I would like to figure out the rate of heat loss of my house. I haven’t thought about this since I built the house and I’m at a loss here about how to proceed. This is an ICF house, and the insulation value of the ICF assembly is always a matter of debate. Some manufacturers are still making wild claims for their products.
The information I have is: indoor temperature drop with the heating system cold, elapsed time, outdoor temperature, surface area of the house.
It seems to me I should be able to calculate a u-value for the whole house from that alone and then work backwards from that, deducting the u-values and areas of the known assemblies to get the u-value of the ICF walls as installed.
More or less.
But the first step eludes me. Anybody got any advice?
Ron
-
ronbudgell | | #126Riversong
This was discussed above.
Ron
-
frenchy | | #127OK so using your numbers a 20% improvement. In addition to that we have the other attributes of ICF..
greater durability caused by freedom from decay caused by moisture or insects {termits, carpenter ants, etc. }
a 200 MPH wind survival capability,
superior fire protection
superior earthquake surviability
faster construction potential
superior sound attenuation
-
MikeSmith | | #132frenchy.... i think ICF's have their place... and compared to standard 2x4 construction, they are superior.... but your reply was incorrect and misleading
....<<<<
OK so using your numbers a 20% improvement. In addition to that we have the other attributes of ICF..
greater durability caused by freedom from decay caused by moisture or insects {termits, carpenter ants, etc. }
a 200 MPH wind survival capability,
superior fire protection
superior earthquake surviability
faster construction potential
superior sound attenuation>>>>>>>>
1st ... the article ( 2d time it's been referenced, BTW ) said NO improvement other that of the R-value of the foam
2d...... if the foam is untreated then there is no freedom from insects, to the contrary.. insects love untreated foam
3.... ok... if you can keep the roof on and the windows don't blow in
4..... not a superior fire protection... foam has a high flame spread... if you want superior fire protection , you should go with cellulose insulation
5... not a faster construction potential at all.. no way.. no how
6.... granted .. superior sound attenuation...
looks like you got 1 out of 6 by my count..... and i like icf's... but a man has to know his limits
Mike Hussein Smith Rhode Island : Design / Build / Repair / Restore
Edited 12/17/2008 2:08 pm ET by MikeSmith
-
frenchy | | #136
1 20% is 20%
2 frankly if water were to affect the strength of an ICF it wouldn't work in the first place.. as for not treating the ICF's Most of those I've seen mention treatment but admittedly I haven't verified all. But I wonder what appeal would a termit have to nest in foam with no hope for a meal someplace? They aren't attracted to concrete.. Foam has zero food value for them.
True they could decide to encamp there because they can. But they can also encamp under a freeway just as well.
3 If the walls will withstand a 200 MPH wind and the roof comes off then replacing a roof seems easier than replacing walls and a roof. Window damage is to be expected.. Pretty easy to replace windows compared to replacing a whole building..
4 Foam does not have a high spread capability. Not as used in ICF's. In fact when I lite it on fire it would put itself out!. Think about the basic fire triangle. You need three things to have a fire.. Fuel source, heat, and oxygen. Granted untreated foam can be the fuel source and sitting in open air it would have oxygen*.. however it has great insulation properties preventing heat transfer.
* however encased in sheetrock on the interior and something like stucco on the exterior access to oxgen is restricted.. Unlike stick building where the consumption of the wood provides it's own access to oxgen..
5 You missed earthquake protection, the forms I used (reward forms) already have that rating and if you think about how they are constructed with rebar reinforcement encased with foam they really are superior to wood nailed together in an earthquake..
6 Faster construction potential?
Absolutely! I've watched experianced crews build with ICF's faster than their counter parts could stick frame..
My own experiance as a complete amatuer was it was the fastest way to build.
I don't doubt for one minute that you could stick frame faster than you could build with ICF's. However look at the experiance level you have stick framing and the same lack of or modest amount of ICF construction experiance. (not trying to deminish any experiance you have merely saying it's tiny in relationship to the experiance you have stick framing)
With experiance we all get better and faster..
7 We do agree on the last point
Replies
That first step might be elusive, since it depends on the aggregate heat capacity of the whole house, including exterior and interior structure (walls, ceilings) and furnishings. Each part of the whole has its own mass and heat capacity, so the total amount of heat lost through the building envelope is total heat capacity times the drop in temperature.
The R value of a material or wall assembly can be calculated from amount of heat required to maintain steady-state conditions. But that's normally laboratory-level stuff, where conditions can be controlled carefully. In a real house environment, you don't have steady state. You've got varying outside temperature, varying solar gain through the day, and varying human activity inside. In a very well insulated house, the human activity can provide a significant part of the heat load. That was the basis for Gene Leger's attempt at building a superinsulated house without a heating system (OK, he had to add a little baseboard heat running off the water heater, later thought he needed only a third that length).
I wonder if you could back into what the ICF wall R value would have to be by measuring heat demand over the whole heating season, and using something like RESCheck to vary the wall R value to match up with the heating degree days for the local weather for that season. The local electric or gas company probably tracks that carefully for delivery and billing estimating purposes.
DickRussell
I understand that the calculation of the R value of materials is a laboratory job - that's why I'm looking for a little bit of real world information.
With ICF construction, the R-value of the assembly is easy to figure; it's the thickness of the foam times the insulating value of that foam, plus something for drywall and air films inside and out. No problem.
Unfortunately, it is true that the house can perform much better than the R-value might indicate. Or so I'm told. I have seen promotional material from ICF manufacturers saying that their houses perform as if they were of R-50 construction. I have no idea how this might be determined, so please don't question me on it. I do know that this house is astonishingly easy to heat, though to a great extent that's a function of design.
Anyway, I was thinking that the time period involved is short, only 8 hours, so that it might make sense to only consider the heat capacity of the air mass enclosed in the house. The temperature of the hard contents would not likely have changed very much, maybe. What's your opinion on that? (I should get about 50 little thermometers and scatter them about so I could know what I was talking about.)
As for the annual approach, Itr would probably be the most accurate way to do this if I could keep track of the heat inputs. But I can't. I might get anywhere between a quarter and a half of my heat from a wood stove.
Ron
"it is true that the house can perform much better than the R-value might indicate"
This is not true. The reason that a simple r-value only calcuation is ususally inaccurate is that it is devised and executed by incorrectly. A structural element that has an a given R value will tranfer heat at the same rate (under the same conditions) whether that thermal resistence is due to concrete, foam, fiberglass or popcicle sticks. The manner in which the transfered heat is manifest in a change in inside air temperature AND personal comfort IS affected by construction details (mass, air infiltration, radiant properties, mean radiant temperature) and other factors.
If the some of the statements being discussed were true, the entire HVAC design industry would be in dissarray. I can attest that it is not. The fact is that heating and cooling loads and transient analysis are performed accurately on a daily basis by the professionals out there that make their living doing so. Manual J is for residential contractors to help them not grossly oversize equipment. That is its sole purpose and the limit of its usefullness.
Heat transfer is a very simple and well documented physical process and it does not change based with application. dTxAxU = h for transmission heat transfer. This applies to SIPs, ICFs, concrete block walls, framed 2x4 walls, those with insulation and and those without. It applie to high mass systems and it applies to low mass systems. It is only one part of the "equation". Wind speed and direction (forced convection), radiant heat transfer, structural heat capacity (related to mass and material properties), solar incidence, outside air temperature and rate of change all modify the the transfer rates.
Heating Degree Day data is a very blunt instrument as well. It is useful in gross energy use estimations only. The idea to measure the heat use over a given period is a good idea, IF you were to take into account the outside air temperature, wind speed and direction, details of solar incidence, the inside air temperature and infiltration and the temperatures of all of the interior and exterior surfaces. Otherwise, the information gained would be general. This is not bad. But on a 20 degree sunny day, I know it will take less gas to heat my house than on a 20 degree windy night.
"Heat transfer is a very simple and well documented physical process and it does not change based with application. dTxAxU = h for transmission heat transfer. This applies to SIPs, ICFs, concrete block walls, framed 2x4 walls, those with insulation and and those without. It applied to high mass systems and it applies to low mass systems."Bear in mind that the heat transmission equation Q=UAdT applies to steady state heat transfer. Seldom in a house is there really steady state. The temperatures are always changing. If an R20 wall had zero mass, the temperature profile and thus heat transfer rate would respond instantly to any change in outside temperature. As soon as mass is figured in, there is time-dependence. The more mass there is, the slower the temperature profile responds to an outside temperature change.True, over an extended period of very cold outside air, the concrete in an ICF wall won't really help. But as Ron pointed out, the damping effect of the concrete can help with the shoulder ends of the heating seasons and any time where there is a large but short temporary dip in temperature.
No, it does not apply ONLY to steady state heat transfer. While it is a simple equation representing a portion of the process (and I clearly stated the transmission or conduction portion of the total heat transfer was just that, only a portion of the energy equation), the transmission heat transfer equation can be utilized in transient analyses. Heat transfer in general terms is made up of conduction, convection, radiation and respiration.
The equation is frequently used in only overly simple models that can only approximate heat loss as a steady state process. There are more complex mathmatics at our disposal than simple multiplication. For quite some time, we have had the ability to analyze systems as a time function.
While it is true that the response of the system is affected by the mass of the system, the thermal resistence of heat transfer through a solid is fixed property of the materials involved. It does not change with temperature (for the temperatures involved in comfort heating and cooling applications) or with the quantity of the material present. If the material remains unchanged, the R value remains unchanged.
Think of transmission heat transfer as an RC circuit. The thermal resistence is the same as the electrical resistence, the mass/heat capacity of the system is the same as the capacitence and the dT is the voltage. This type of transient system is easily modeled by a first year engineering student. Not quite within the capability of most elementry or even high school kids, but simple enough.
I am unclear as to what you mean by "the temperature profile". Please define what you mean by this. Are you talking about the temperature gradient through the element? The inside air temperature over time?
We don't really disagree on the fundamental heat transmission equation (Q=UAdT), and probably not on the proper use or misuse of it.
In the context of the Ron's opening statements, he was hoping to come up with some sort of overall wall R value, for purposes of discussion with others on the merits of ICF wall construction [Ron, correct me if I haven't got that quite right]. The only real R value for the whole wall that would mean anything would be as measured for or applied to steady state conditions. Using the whole wall R to compare perceived performance of high-mass and low-mass walls in varying temperature scenarios would be misleading.We both agree that one could, with the appropriate technique, integrate over time, using the fundamental equation to calculate heat movement through each differential slice of the wall, to get increments of heat moved through it according to the R and temperature difference across the slice. That increment of heat tends to heat up the adjacent slice, which in turn is losing heat to the next slice, and the temperature of any slice goes up or down a bit according to the heat imbalance over the time interval and the heat capacity of that slice.My statement about the fundamental equation not applying to non-steady state conditions is fair in that it can't be applied in simple fashion to calculating the rate of heat movement through a whole wall that has mass and is made of different materials if temperatures aren't steady. Nor can it be used easily to back out a whole-wall R from some heat measurements done for the whole house over too short a time.By "temperature profile" I mean how the temperature changes from one side of the wall to the other (plot of temperature vs distance across the wall). From inside to outside, there would be a large drop across the inner foam layer, then a fairly small drop across the fairly conductive (low-R) concrete, then another large drop across the outer foam.A sudden large change in the outer temperature will not result in a rapid change in the temperature profile across the inner foam and concrete. The profile across the outer foam layer will respond fairly quickly, due to its low mass, and the rate of heat loss from concrete to the outside will increase. The rate of heat loss from inside the house through the inner foam layer will hardly change at all at first. It will take hours for that rate to increase. Clearly, the overall temperature difference from inside to outside at any instant in time can't be used to calculate an overall wall R value, knowing nothing else.
Dick,
You've stated my objectives quite clearly, but I really don't want to try to limit the discussion. This is very interesting.
The temperature profile, using your definition, of ICF walls is not as straightforward a matter as all that, though. First, as the poster above pointed out, the concrete core can conduct heat both from and to the ground below. Second, the concrete core is nearly open to the inside, covered only with a sheet of drywall, around the perimeter of every door, window and other opening in the building. The temperature of the middle of the core will not ever, in a steady state of heat flow, be the average between inside and outside.
Ron
Good point about conduction of heat to/from the ground, up through the concrete core. I guess this ought to help at both temperature extremes. Assuming symmetrical foam-concrete core-foam (and ignoring conveniently the areas around windows and doors), consider the extremes.In the coldest part of winter, the core temperature might be significantly below the temperature of the ground (mid 30s vs. mid 40s or so) if ground heat were ignored. Heat will rise up through the footing to keep the core warmer than it otherwise would be, although the part above grade would see the effect the least, being separated thermally from the footer by the most concrete "R" (96" times 0.08/inch is r 7.7).All summer, the ground will be cooler than either inside or outside, so the core will be cooler than it otherwise would be without ground conduction.Now, as to comments from others, I don't disagree with the fact that heat lost by the core to the outside has to be made up by the heating system (other than what the ground might provide). Most of what I have said is aimed at showing how mass makes for very long times for the temperature profile to respond to temperature changes on either side and how that makes calculating whole-wall R from temperature changes elusive.With a concrete core wall (high mass, insulated well on both sides), the response time is very long compared to the day/night outside temperature swings. Clearly there is hardly any time when the profile is steady. Without a lot of detail on temperatures within the wall vs. time and a detailed transient (computer) model to use, trying to use drop in inside temperature over a period of time to back out an overall wall R value (the original goal) will indeed be elusive. A more accurate value can be estimated from the published R values of the components of the wall, but the usefulness of that number is limited by the the complexity added by window and door openings, as Ron pointed out.That leaves two other issues. One is to what extent, if any, there is a dampening effect of high mass on overall heat loss when there are significant day/night outside temperature swings. Everyone will acknowledge that swings to either side of inside maintained temperature result in reduced or even no cost at all for heating during such times. IIRC, one of the ORNL papers that dealt with the benefits of various configurations of high-mass walls in different climates did show some limited benefits in other climates without above/below temperature swings. I'll look for it, unless someone else finds it first (I have to check that one mentioned earlier in this thread).Finally, there is whatever "perceived performance" there might be from an ICF wall. I guess that's harder to quantify or even define. Are we talking lower than expected fuel bill? Is this just due to lower air leakage?
Edited 11/26/2008 9:18 am ET by DickRussell
OK, that earlier URL posted did lead me to what I had seen. In particular, a graph of possible energy savings vs. total R value of the wall is given for multiple locations:http://www.ornl.gov/sci/roofs+walls/research/detailed_papers/thermal/index.htmlThe plots seem to show at least some benefit, however small, for all locations for wall R above 7, for ICF walls vs conventionally framed walls at the same R.However (sometimes a gotcha), one level before I got to that paper was another link, to a Canadian measurement:http://www03.cmhc-schl.gc.ca/b2c/catalog/z_getpdf.jsp?pdfkey=5754896432760327018176763740702198818224598700828122734/65863.pdfThis showed no apparent gain in R value compared to that of just that for the two layers of foam on either side of the concrete (see page 6 of the paper for conclusions). I can't say if the Canadian measurement and the ORNL modeling are comparing apples/apples or mixed fruit.
Edited 11/26/2008 10:03 am ET by DickRussell
Dick,
I was very interested to see in that CMHC study that the temperature of the cpncrete core varied very little from its average - only 3.25 C up and down, though the outside temp varied between 0F and 50F during the test period.
So they concluded there was no difference between an ICF house and a house built of the same amount of foam alone.
Yet an ICF house will still perform better than a wood frame house with glass insulation which has the same total R-value. Is this because there is something funny about the rating for the glass/wood house?
Ron
The problem with R ratings is they don't take into consideration what's not insulated.
There are studs every 16 inches some times doubled up or more. That's 1 1/2 inches of no insulation every 16 inches sometimes 3 inches or even 4 1/2 inches of no insulation etc..
At best a stick framed wall is 80 % insulation not 100% insulation like ICF' s or SIP's That's one of the reasons fiberglas reads lower.
No, the studs do have an r value. So does every other component. A good program or a competent designer takes all that into account.
So you claim the studs have an R 19 value? I doubt it.. technically you are correct in that they have some nominal value. Heck a coat of paint has some nominal value.. For ease of discussion we use broad strkes here because the whole concept is so complex a person can easily get caught up in the minutia of details and forget the overall picture.. Indeed the goal of this discussion is being able to quantify the energy savings of one form of construction over another.
The bottom line? In my case the energy savings are massive.. I doubled the size of my house. Tripled the number of windows and using my same furnace I cut my peak monthy bills from $500 to $200
Further in the summer I eliminated whole months where airconditioning was required and last summer I used the A/C only 10 hours total! (that with one less A/C unit!)
I'm guessing most of the heat energy savings is from reduced air leakage. On the A/C side, you likely have the benefit of the daily temperature swings that really help take advantage of the mass thereby protecting you from the extreme during the day.
Are you slab on grade?
No, I'm not slab on grade. However to be fair, the summer heat deal is due in part to location. While the previous house was located in the same place. It failed to take advantage of the microclimate locally and as a result added a great load onto the house in the form of heat gain..
That plus really effective insulation prevents heat gain during the hot summer months. I've actaully been somewhat chilled on 80 degree days with high humidity and need to go outside to warm up.. It has to be well over 90 outside with near 100% humidity for me to want A/C on.. (and since I'm so fat heat really is my enemy)
There is a great deal of truth in that the houses mass contributes to my comfort, walls are 18 inches thick. With tons and tons of timber mass inside to cool off at night. and gently release that chill into the hot house during the day..
You can see photos of it at 85891.1& 94941.1
No, Frenchy, he said studs have an R value -- about 1.4 per inch. That works out to about 5 for a 3.5" stud -- not R19, but not-trivial. Each 16 inches comprises 14.5" at R19 and 1.5" at R5. That yields an aggregate R value of about 15, if I figured it correctly. And of course that's not taking into account the R value of the siding, sheathing, drywall, etc, which likely add another 4-5.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
DanH
siding sheetrock etc. are common on all homes so since we are comparing efficency of insulation systems we effectively ignore those numbers..
Designers and archetects also ignore the studs when doing their energy loss calculations but even if we use your numbers that's only 26% of the effective thermal protection on at least 80% of the wall.. with a 2 story building that can easily amount to 40% of the wall or more if large windows are involved..
A basic 2000 sq.ft. 2 story house with a R rating of 19 might actaully net out to be R 13.4 in a relatively typical house and R 16.6 in a home with no windows or doors..
> even if we use your numbers that's only 26% of the effective thermal protection on at least 80% of the wallI don't understand what you're trying to say there.> A basic 2000 sq.ft. 2 story house with a R rating of 19 might actaully net out to be R 13.4 in a relatively typical house and R 16.6 in a home with no windows or doors.. And those numbers are consistent with my back-of-the envelope number. Far better than "26% of effective thermal protection".
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
R 19 compared to R5? thats 26% as effective as an insulation material. Studs are 20% of a wall plus windows and doors.
But you said 26% effective on 80% of the wall.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
OK I put it wrong. Hopefully that didn't cause too much lost sleep..
"Designers and archetects also ignore the studs when doing their energy loss calculations..."
I can't speak to what architects do, the smart ones hire HVAC design engineers, and we do not ignore anything when doing our energy loss calculations. Walls, doors and windows are treated as separate elements and all accounted for as well. I think I understand the confusion. Based on your statement, you did not realize that all of these things are considered in an energy analysis (heat load calculation). They are and usually, they are accounted for in a thorough manner. Each wall, each window and each door as well as foundations (above and below ground) roofs, ceilings and any other openings, penetrations, etc. A coat of paint, BTW, has no measurable R-value and IS ignored, with the exception that the color will affect solar heat gain for cooling.
We are saying basically the same thing simply caging it diverant verbage..
However the odds of anyone hiring a HVAC engineer to do these calculations are virtaully non-existant.. I know of several multi million dollar homes where the old rule of thumb HVAC installer does a quick rule of thumb and gets the bid because he's the low bidder.. The chance of a moderate income home builder doing it are simply non-existant..
I was hired as a design engineer, to design HVAC systems for three houses, which included detailed calculations, and hired to review and offer remedies for several other poorly ROT designed systems. As a "sales engineer" i.e. inside sales and technical support, I designed a few more for my customers, as "part of the package".
Regardless of how often these services are utilized in the residential market, the point is that your assertion that R-value is meaningless is incorrect. I do agree that the data available is often misused or utilized in incomplete/partial analyses.
I'm sure it does happen Tim.. I simply cannot recall when I've ever actually seen it done and I've been involved in some really expensive (tens of millions) dollar homes..
With regard to the abuse of R values.. and the real world. Somehow people believe that all R values are the same. Plus somehow R values indicate with what sort of expense there will be in heating/ cooling their homes.
We know for example that wet or damp fiberglas has a totally differant R number than test results indicate.. We also should be well aware of airflow through fiberglas can effect it's actual rating.. So as built is far more important than design concepts..
Frenchy,
You may have not yet come to this realization, but your experience is limited. It is true for all of us. There are large facets of the building industry, residential, and otherwise that you have not personally experienced. You are not, nor have you ever been directly involved in professional HVAC services for single family homes, multifamily homes, commercial, industrial or institutional buildings. But because you have not personally experienced competent HVAC design, does not mean it doesn't exist. You have never been involved in professionally analyzing the heating and cooling loads of an occupied structure. You have never been professionally involved in the consulting engineering or architectural engineering occupations. I'm willing to bet, just as I know next to nothing of the details of your profession, that you have VERY limited knowledge of what these people do and how they do it.
"wet or damp fiberglas has a totally differant R number than test results indicate"
I've never seen test results for wet or damp fiberglass. Or wet or damp cellulose. Or rodent shredded foam. Or any other compromised material you can imagine. IF the internal insulation in walls is getting wet, regardless of the material or the cause, you have much more serious issues to be concerned with than the insulating value. I do remember that you royally hosed your previous house and experienced this. Incompetence and gross negligence cannot be accounted for by even the very best designers.
Air flow through any structure has to be accounted for in the heat loss determination. I would account for more infiltration in a framed wall than a masonry wall. Infiltration/exfiltration occurs at construction joints not throughout the entire wall. Very small portions of the insulation are subject to airflow. IF a significant portion of your fiberglass insulation is experiencing airflow, check the side of your house! It might be gone. You can make up as many scenarios as you wish. All construction has joints that are assembled with varying precision and attention to detail. ALL structures leak when the wind blows. Competent design takes this into account.
Which part of this is unclear?
As I said, I accept that you have some experiance which I have not seen in my neck of the woods.. I am also sure that you are skilled at your task.. that's not in question..
I do hope that was plain enough.
It is true that I had a bad experiance with both fiberglas and celluliose insulation with the old house,, however none of that was caused by incompetance or neglect. Indeed my frequent checks and searches failed to find a leak or flaw in the insulation package.
When I tore down the old house I looked carefully for a source of leakage as the house came apart and never found any. I would have loved to found one to point to as the cause for the poor performance of my insulation.
However I'm sure like me you've seen plenty of flaws in insulation envelopes. I know with the thousands of remodeled homes I've seen over the past 2 decades it's actually unusual not to discover nasty flaws.
That's why I'm such a fan of ICF's . If there is a significant flaw the concrete spills out and creates a mess.. Unlike every other insulation package it's not done as an after thought. It gets complete attention or the pour makes a mess to punish the inattentive..
That too calls into question your assessment that all construction has joints that cause air leakage. I'm not sure what joints you're speaking about in ICF construction. (another point in favor of ICF construction..
I do know that in spite of fanatical attention to detail joints on my SIP's were not air tight. Fortunetly SIP's come as large as 30x8 so joints are at a minimum. I doubt any SIP joint can be made air/water tight. Which makes stick framed construction even worse..
Poured concrete, whether inside of a foam form or not, tends to be joint free. Houses that have foundations poured in ICFs have construction joints. The walls sit on top of the foundation. Those walls have openings for doors, windows, wall hydrant and electrcical outlets, regardless of their construction. On top of those walls is a roof structure, that also contains joints as well. Hence the statement that ALL buildings have construction joints and all leak. This is not an opinion.
I am not debating the benefits and drawbacks of types of construction. I agree that SIPs and ICFs have great benefits. Those benefits are real and quantifiable and do not need to be exagerated by extreme examples of poor construction.
If you had wet insulation it was due to a failure. Since you did not identify the failure, you really can't say if it was caused by incompetence or neglect, can you?
Air flow through fiberglass can absolutely affect its rated R-value. That assumes it is applied in a manner and in construction that is contrary to what it was intended. I've seen the guys saying their cellulose wet applied is superior because it reduces this ... they show me a box to demonstrate how easily fiberglass allows air flow through it by fan forcing air through the two samples.
But ... that isn't the real world. Our walls are typically not exposed to free air pressure/air flow that will do this. We enclose fiberglass in wall cavities that largely, while not air tight by any means, are an enclosed volume. As such free air flow into and out of that cavity is significantly limited.
Not disrespecting your points or your love of the ICF. Just trying to maintain some perspective here and add some food for thought.
With all due respect, your experiences are yours. We've probably all seen horror stories regarding all kinds of things. I'm guessing the failures you've seen, though are generally the exception, and not the rule. You've maybe seen more than your fair share. That's OK ... you support a reasonable alternative as a result. It's all good stuff.
Excellant points all of them..
What is still really needed is something so the average home owner can say this is the best value for me based on these factors..
Things as they are now are pretty vague to the average homeowner who's more concerned with Granite countertops than details about insulation..
That I think is the point of the OP
My claim about reduced costs while certainly valid and capable of standing up to scrutiny is not a standard whereby someone could justify a differant cost structure..
Just for the record, If tomorrow someone came up with an easy way to inject used potato skins into a superior insulation I would drop my support of ICF's and support used potato skins. (or whatever)
Absolutely. You have to appreciate the 'average homeowner' for he can much only appreciate that which he can see and touch and not the concepts by which his house will save him big bucks in energy. You see two cars ... one looks like a red Ferrari (with a 2 cylinder engine) and one looks like it had been stomped on by bigfoot (although with a very nice drive train) ... and which are you going to pick out of a line up? People don't/can't always look under the hood. Aesthetics does have value, too.
Have we beat this horse to death, now? :) To the OP ... sorry. Nothing like moving in on someone else's conversation and taking over.
Clewless1 and everybody
Don't worry about me. I got what I wanted out of this.
I originally thought I could calculate the as-built heat loss of this house from a short term temperature drop, but was convinced that an annual approach was the only solution.
With a bit of work, I came up with a number for annual enery consumption, did the calculation, corrected a few mistakes and found that that calculation and a heat load calculation I did from the drawings came up with the same solution.
Which surprised he!! out of me.
Anyway, I really appreciate the help and advice.
Ron
Plenty of seasoned engineers will tend to generalize when doing design heat load calculations (which, by the way is a totally different, albeit similar, animal than "energy analysis"). I know of few engineers that count the framing in heat loss ... I mean count each framing piece ... they may make a generalization about the framing to insulated portion ratio. They may even occasionally do a fairly accurate calc. But as a rule, they don't.
And rightly so ... While accuracy is very important, precision is not (there is a difference). I can calculated my heat load to 63,126 Btuh ... or I can calcuate it to 65,896 Btuh ... but the choice of equipment is limited to large increments made by manufacturers. Also, there are enough unknowns that make precise calculations a waste of time. We can only guess about things like air leakage in a building. Is it 0.35 ACH or is it 0.50?
You say you account for every penetration ... of every pipe and J-box? While your point is well taken, you are making it sound like you leave no stone unturned and I suspect that while you sound like a meticulous person, you are not quite as detailed as your words literally say. Even you make generalizations, I'd bet.
I get your point, but the less informed reading this may take you more literally and begin to think that is what they should expect from their engineer or HVAC installer.
"they may make a generalization about the framing to insulated portion ratio. They may even occasionally do a fairly accurate calc."
When I performed manual calculations, I did a stick, by stick analysis of a wall, ONCE. True, most frequently, in manual methods, an average area ratio is used. I found that in typical construction (2x4's 16" o.c., single bottom plate, double top plate, 8' ceilings, etc) the ratio is 85/15. Using a software and selecting the appropriate wall type, that is accounted for automatically. I do not manually run heating and cooling loads any more, except in an estimating mode.
Obviously, an energy analysis is different than a design load determination, though they both have to begin with accurate construction details. Else, they are both guesses.
As far as air inleakage/outleakage, again based on manual methods and typical construction, I would estimate in ACH based on the number of exposed walls (in a room by room analysis. ASHRAE covers several methods I do not use, such as crack length and characterization.
Every penetration in detail? No. Every element in developing wall construction types and associated R/U values, yes. In a typical manner. There is a level of practicality and expediency that requires ignoring certain minimal details. Absolutely, generalizations are made. As I develop the load calcs, though I do know if my loads are "skinny" or "fat". When equipment selections are done, I take that into account.
My point was not to delineate the details of performing manual heat load calculations, but to express that the type of construction is actually taken into consideration when performing such. Can you install a fiberglass batt, nominally rated at R-19, in such a manner that it provides only R-8? Not unintentionally, and even then it would be difficult. The example is BS, made up to exagerate a fallacious argument. The fact that framed walls have a composite R-value based on the entire structure and not simple the nominal value of the insulating material was also a lost point.
Agreed. Just making sure the words aren't misconstrued.
Every item has an r value. You just have to take it into account. I never claimed r19 for wood. If you want to be precise, you need to know the species of wood.
However, for broad strokes, r15 works for a 2x6 wall before windows and doors.
R15 is too generous.. I believe it works out to be R13 average a stud is generally considered to have a 1.4 R value per inch
wood for framing has a nominal R-value of 1 per inchso a 2x4 has an r-value of 4 for a width of 1.5 inches2x6 has an r-value of 6 for 1.5 inches of wall typically the framing takes up 10% of the wall area and the inslated to full depth areas account for the other 90%to get a full composite wall you have to add the values for the inside air layer, the gypsum wall board, the sheathing, and the siding
the outside air layer usually is not counted because of wind washMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
Well Mike you are free to use any formula you wish however the building code actually uses the 20% number.
Second a 2x4 isn't 4 inches it's 3 1/2 inches. a 2x6 is also only 5 1/2 inches. Plus in a lot of places studs are doubled tripled or even more. You did remember to subtract the windows/doors from the total didn't you?
That does not take into consideration any areas that are insulated to less than optimum. it's all to easy to stuff insulation into a wall and fail to get the corners proper or allow electical cable to hold it away and compress it too much around the romex.. etc..
frenchy...i started doing heat loss calculations in '75 when we built the first solar heated home in Rhode Islandwood can be 1 to 1.4-r
if you use one for nominal size you will be right onwhat we are looking for is a reasonable aproximation of the area being caculatedand yes... i calculate all factors including band joist areas... i calculate for edge loss on doors and windowsi use 70 deg iinside design tem and 0 deg outside design tempmy heat loss calculations are all based on ashraewe do :
below slab loss,
slab edge loss
window loss
door loss
NET wall loss
band joist loss
ceiling loss ( attic or cathedral ceiling )and any peculiar areas that are insulated differently than the typical.... eg: garage wallsso yes... i use 1 per nominal inch.... and i have calculated framing content many times.9 / .1 works for us because that is how we frame.... nothing left out.... but no extra stud either......i want to know what i'm designing our heating systems to overcome... and since we zone our systems.... i want to know.... total envelope and room-by-roommy numbers have been pretty consistent for the last 32 years.... and the formula is still the same.... i know what the dimensions of a 2x4 / 2x6 are.... i know how we frameMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
Mike Thus is the weakness of the internet. If we were discussing this together I could almost instantly see where you were going with your statement and wouldn't have bothered you with my comments.. However since I can't "read" you like I could in person I make assumptions and sometimes those assumptions are going to be wrong..
Inherently we are going to be at odds because I believe stick framing is as antique as a Ford Model T. Your approach is with regard to running a bushiness and you have an established reputation you want to protect.. At your age you do not feel comfortable doing a radicle change in your approach to construction and that is certainly understandable..
Imagine if SIP's, ICF's, and other modern construction techniques had been widely available as you were starting out. (they were available just not widely available) and you had learned how to build with those efficiently. If instead of 98% of the houses stick built we'd learned from the first energy shortage and real energy efficiency had been the norm. SIP's and ICF's would be the dominant method and all the short cuts skill sets and specialized equipment had been designed with those in mind..
Take a novice builder and have him build a stick framed house the differance in speed and perfection is the same differance most builders have when they approach SIP/ICF construction. They don't know the short cuts, tricks, and ways to gain speed. They don't have the specialized equipment required and everyt step is a learning process.
Once they are on equal footing watch how quickly stick building becomes a unique subset like timberframing..
frenchy.....98 % of existing housing stock is stick framed.... and 75% of our business is not new construction nor additions....it's remodeling stick framed structures...
when we get done.... our structures always have less heat loss and lower cooling loads than when we start.... always... we design it into our jobsMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
Mike
I'm afraid that's like saying your Model T has a self starter when the competition is driving modern vehicles.
It's fine for you and it's all your customers want from you but if that home is going to remain thru the 21st century it is at risk of being either torn down to put in some really efficent insulation or so dramatically recreated that most of your work will simply disappear into the bin.
It is a way to make money and probably makes for a relatively easy sell based on your reputation etc..
I would think that foresight should require you to at least make the insulation package state of the art rather than a compromise system that's more than 50 years old..
frenchy.... i'll put any of my superinsulated structures against anything you can conceive of.... and we'll see who has the better envelope... sips and icf's are fine... especially compared to conventional insulation specs
what can you do for R-14 slabs ?
r-25 ( or r-32 ) walls ?
r-60 attics.... ?
you still don't have a clue , do you ?
Mike Hussein Smith Rhode Island : Design / Build / Repair / Restore
if you are working with sips, what does your mfr. spec for an r-value ?
what does your mfr. use for a siding / trim nailbase ?
ok... now we have our walls ... what are you going to spec for a roof / cathedral ceiling system ?
c'mon... gimme a spec and an r-valueMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
well my roof over the cathedral ceiling system is R50+ (except the peak where it totals R100+)
I say plus because 48" o.c. I have timbers up to 14 inches thick. My ceilings are also R50 the walls are R30+ because again every 48 inches there is an additional 10 inches of timbers.
Those timbers are on the seams which have splines and glue sealing them and 12 inch x 1/2 inch stainless steel lag bolts connecting them in a clamping method. (yeh the walls are between 16 & 18 inches thick.
You've seen the pictures of my house under construction. If you forget the pictures are at 85891.1& 94941.1
How many times will you bang your head against that brick wall before you realize that reasoning or applied experience do not trump magic?
yeah.... but i love frenchy.... he's my manMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
Tim
Magic? I just thought it was hard work and sacrafice.. what part do you figure is magic?
It is not magic, Tim.The shellac seals all of the air leaks and add R-20..
William the Geezer, the sequel to Billy the Kid - Shoe
whoa...... don't choke on that tongue in your cheek
good to see your smiling face , billMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
The "magic" I was referring to is that conjured by a particular prolific poster, that frequently changes facts and reality to conform to whatever version of reality he happens to be BSing on at the time. It was my nice, euphemistic way of pointing out the lies and deception, bent and twisted factoids and the like.
tim.. i think you're being harsh....and i don't think he has ever lied or intended to deceive
he does have a bias , but i wouldn't be judging his intentions... which i think are honorableMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
True, I am being harsh. History over the past few years contradicts your beliefs, generous as they are. I concede the intentions are not to deceive. The arguments, none the less, are based on supposition, guessing and frequently, fictitious "facts".
i know... but i still love him
Merry Christmas, TimMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
And to you, too!
I do enjoy the discussions, though I may disagree a lot posted, I still enjoy the interest and passion for the subject.
Well Mike,
I believe my house will answer all of your questions.. How many homes do you build or rebuild where you double the size of the home and triple the numbers of windows yet using the exact same furnace cut monthly heating bills from $500 a month to $200 a month?
At least we are in agreement that SIP's and ICF's are fine What you left unsaid but I'll say is that perhaps you do have great attention to detail, that is not shared by the vast majority of builders.. I've seen the heating and cooling bills of my neighbors. They've seen mine.. they are envious.
typically the framing takes up 10% of the wall area and the inslated to full depth areas account for the other 90%
Mike, when you say typically are you speaking of the homes you build or a typical home?
I believe energy raters assume a default value of 23% framing for a wall with studs spaced at 16 inches on center.
The studs alone take up almost 10%..then there are all the extra studs at corners,windows and partition intersections...and don,t forget the typical 3 plates and the headers.
I admit that we can do better than 23% with a little thought and planning..but 10% is unrealistic.
Never thought that I would agree with Frenchy.
Edited 12/14/2008 6:42 am by homedesign
since you are getting specific. In my circle ... most houses are 2x6 @ 24 oc. Also, if you use some advanced framing techniques, you can minimize the double/triple studs.
Also SIPS have framing every 48 oc, right? plus around windows, doors, etc. Yes, approaches 100%, but not 100%. I'm guessing even ICF has framing around the windows/doors, maybe not.
Edited 11/27/2008 9:52 am ET by Clewless1
No there are no studs in a SIP's or ICF wall. while there are wood framing members around window and door openings in both, those do not carry to ground like normal stick built houses do. You simply cut a hole where you want a window stick in a buck to nail the window to and poof window! For the sake of energy calculations you add that together with the window for window/door loss.
Around here stick framed houses need a minimum of 2x6's 16oc to meet insulation codes and if you plan on using many windows you have to place them carefully in order to meet heat loss calculations.. It's normal to have only one or two small windows on the sides of homes in order to meet those rules.
Further single 2x6's or whatever will not meet load calculations on most 2 story homes.. (normal due to extremely expensive land) Don't forget our roofs need to be much better built than many roofs due to winter snow loads and the fact that we are in Tornado alley. It is common around here to use nearly solid walls of 2x6's to put in the large picture windows most want for the fantastic views overlooking the lake..
SIPS I've seen always have a framing member at the edge, top, and bottom. It usually just ain't OSB on foam and nothing else. You're right about the windows and stuff, but you did bring up the issue of framing and said 100% of SIP is foam ... and it ain't quite. You put a lot of windows and doors, my gues 2-4% is framing. Just the one edge of a 4x8 panel is 3%, so it may be more than you think.
2xt @ 16 oc minimum for energy ... so you can go 24 oc there? if so, that reduces your % framing a lot. I've never thought of 2x6 16 oc if you don't need it for structure and you can go 2 stories @ 24 oc w/ 2x6 (just finished a house w/ that and the BO approved it and they were sticklers). I used no header over windows on gable end walls and wherever possible a single 2x6 or 2x10 or whatever on bearing walls ... a full 6x10 is usually not required structurally on the ground floor. Even if you need more than one, two spaced w/ 2inches a foam will do the trick on a header. Also if using a single header, you can let the header into the stud eliminating the jack stud.
3 stud corners, too. Advanced framing is the way to go. You have to pay attention to some details, but you reduce a lot of framing. Then you can always substitute 1/2" polyiso anywhere you don't have a shear panel to provide a thermal break. Don't they do these things in Minnesota? Snow load on my house, I think was 50 psi I think (lots of wet snow out west) and 100 mph wind load.
While not an advocate of eliminating the view, I also don't think you need a solid wall of glass to get your nice view of the lake. Views don't have to be uniterrupted expanses of glass. The classic craftsman style of three large windows set a very nice stage for very nice views surrounded by nice architectural detailing ... now the view and the house begin to merge. Small snapshots of views work well to keep life interesting. Especially in Mpls, a view looking north can feel mighty cold during those -20 winter days.
SIP's come up to 30'x8' as a standard size and if the wall or roof is longer than that they simply spline the panels together, no transmitting member like stick framing.. My north wall is 50 ft. long and 24 feet high. Other than windows the only 2x materiaL IS AT THE EAST END & WEST END, TOP & BOTTOM.. Think of how much wood is required to stick frame a wall like that!
No we can't use 24"oc because it's not structural enough. (snow loads and wind load requirements).
When you pay a million plus for a 50 foot lot you want a lot of unobstructed glass viewing the lake you're paying for. If you look at my pictures 94941.1 you'll see I didn't go as crazy as most did. However I was only able to achieve the required load strength because of the use of doubled timbers. Most houses have solid 2x material on the lake side.
Foam as a shear wall might work where you are but not here.. since many homes have stone or brick exteriors they are required to have 3/4 plywood. It's rare that I ever see built right used and never on homes on the lake side..
Clewless,
I think that double element headers are always better than single because they will likely resist twisting better as they dry - as long as they are nailed together well. I would find a single element acceptable only if it was small, such as a 2 x 6.
I agree completely with your views on window size and I have wasted unspeakable numbers of hours trying to convince customers to see the light, so to speak.
I think I can recall one of the essays in "A Pattern Language" suggesting that a view glimpsed remains more interesting and adds more to the house's environment than if it was very prominent.
That's not even thinking about the heating and cooling problems you can get yourself into with very large windows in a house.
Ron
Headers can be e.g. LVL and such, too if you are worried about twisting.
People can be so irrational, huh? ... referring to the window thing.
I have just finished re-computing the heat loss for this house and I've come up with some peculiar results.
First, I remembered the original badly. The calculated heat loss at t-ext of 5F is just under 18000 btu/hr. That's using an R-value of 22 for the ICF walls, which is 3/inch thickness on 5 1/2" of foam. I added nothing for concrete.
Then, I converted the estimated annual heat loss of 70,000,000 btu over 5525 heating degree days into the heat loss over (70F-5F) = 65 heating degree hours so that I could compare that number to the first calculation. That value is 13,700btu/hr heat loss, though there is some uncertainty in the amount of firewood consumed and in the amount of electricity consumed which is actually transformed into usable heat.
Anyway, the actual heat lost is less than the theoretical calculation by 4300 btu/hr - over 30%.
The peculiar thing is that in order to get the computation to agree with the actual, I had to increase the R-value of the ICF walls in the computation to R50.
I think we all agree now that that isn't realistic, but it's a funny coincidence.
The truth is that, given the uncertainties, unknowns and several factors simply not considered here, I think the two numbers agree surprisingly closely.
Ron
Very interesting conclusion indeed.
There is an empty ICF home near here that hasn't sold due to the economy.They have the thermostat at 40 degrees and even though the lake is frozen solid and we've had whole weeks where the temps didn't get above freezing the furnace hasn't come on once. Solar gain during the day had kept the place warm enough.
Just guessing but I'd place the size of the house at the +8000 st.ft. size. No special efforts were spent in making the house tight. The contractor who built it used the house as a scam to steal over $3 million dolllars from a local bank that financed it.. He obtained a $5+ million dollar loan because he'd been an industry leader of really high end local properties.
Instead of his usual high end finish work he used cheap contractor grade materials, got a certificate of occupation, collected the last of his money and left for parts unknown..
frenchy,
so he took off with the cash adding just a little bit to the level of distrust of people in my business. Well, I suppose if he hadn't then the bank would have merely given it away as an executive bonus or it would have gone to the lawyers for some protracted frivolous lawsuit. But it sucks to have to put a contractor into such company.
As for the house, I can see that being achieved easily. The bigger it is, the more volume you can enclose with proportionally less shell. That's why so many multi-unit multi-storey jobs around here are ICF. On the bigger jobs, the payoff comes sooner.
Ron
There's actually more to the story.. Apparently the contractor was always spending slightly more than he recieved and making up the differance by taking from the deposit previous owners gave him to get in line with him. Once that ended Conjecture has it that he knew the end was near.
I've seen several of his homes and sold equipment to several builders who worked for him. His homes were stuning. The detail was meticulas and there was always a surprise or two in each one.. Hidden stairs,, fanatastic built ins, One had a stunning view of the lake even though the bedroom was in street side of the house while still providing complete privacy for the owners.
Wait ... I'm lost. You are trying to simplify again and are missing some pieces. Also I can't read your attached file w/ .ods extension.
Confused about your construction 3 inch thickness over 5 1/2" of foam? Not sure what you are saying. R-22 of styrofoam (expanded polystyrene, I'm assuming) would be about 6 12" at 3.3 per inch (not sure if that R-value is right).
Play w/ numbers enough and you can seemingly get correlation.
Clarification: You take your HEATING total load multiply by your efficiency (or median efficiency) divide by HDD and divide by 24 then multiply by delta T ... that would be your theoretical design load.
You're right, though in your calc in that your real world result is say 30% lower than design. Unless you heat 24/7 at 70 deg setpoint, you will always fall short of the calc'd design value. Also, the 5525 HDD is at base 60. Not sure why it is at base 60 ... assumes you set your stat at 65 I guess?
You don't use ALL your energy for the calc, either. Just the heating side which I think you said was 40 million Btus ... w/out the combustion loss. Not sure what you used for combustion efficiency. 0.70 average? Lower? Not sure what your ratio of wood to oil was (I didn't estimate it).
So saying your 40 mil is right. Divide by HDD x 24 and then multiply by 65 and you get roughly 19,000 btuh design heat loss. Looks good so far.
Also remember that average HDD can vary from actual by +/- 25% and more during any particular year. So the year you used 40 MBtus may have been 'unusual'.
I've done calcs like this my whole 30 yr career. It's important to check assumptions and be accurate (which is different than being precise). Sometimes you have to look at things mathematically a couple of different ways, too ... kind of cross check your thinking a bit.
Clewless,
Thank you.
You are exactly right. I made a stupid error in calculation. Actual heat loss is 19,600 btu/hr.
The ods. file is an Open Office spreadsheet calculation of theoretical heat loss. I thought most spreadsheet programs could open it. I have changed it to reflect your k value of 3.3 for the EPS foam in the ICF wall. My walls have 5.5" of foam, which is 0.5" more than most.
I think I chose to use the base of 60 in the HDD because we would never turn on the heat if the outside temp was as warm as that.
Then , what I end up with is figures that are identical for calculated and actual heat loss. What an astonishing coincidence!
This is the spreadsheet:
Heat Loss T=5F
surface
area
R factor
ext temp
int temp
heat loss/hr
ICF walls below grade
700
18
45
70
972.22
ICF walls above grade
1810
18
5
70
6536.11
windows
324
3
5
70
7020
doors
65
7
5
70
603.57
basement floor
821
10
45
70
2052.5
Insulated ceiling
700
40
5
70
1137.5
Roof – rafters
336
25
5
70
873.6
19195.5
I've just been reading the replies posted since late Wednesday. Not much to add, although I thought throw in some numbers I've seen.Typically, the R value I see for EPS (white) foam is 4.0/inch. The XPS (pink or blue) typically is stated as 5.0/inch. I looked up R value for studs, found spruce/hemlock at a nominal 1.2 to 1.25/inch. A very hard wood was more like only 1/inch. Then, too, with the way tables of data are collected and sometimes of questionable origin, one might well find a table with differing values.Edit into the middle: Regarding HDD (heating degree days), as I understand it, the idea is to provide a means for the fuel companies to be able to compare severity of different regions for purposes of estimating when to make fuel deliveries, based on past fuel consumption history and present HDD since last delivery. Using a base temperature (65 is what I see also) is a means of allowing so many degrees to account for the "free" heat provided by solar gain, lighting, cooking, TV, etc. that make up the heat loss and keep the inside temperature constant before the heating system has to click on. Clearly, a very well insulated house will hold temperature below he 65 established quite some time ago. Also as clear, the point where the "free" heat isn't enough depends on what human activity goes on in a particular house. I did want to point out another thing, though not for the regulars posting here who are well-versed in doing heat load calcs but more for the casual readers just interested in this sort of thing. One doesn't have to use rules of thumb (and certainly shouldn't for either heating system or A/C design for any new structure) to figure out what load to expect. The numbers can be calculated in a fair amount of detail, and different construction and insulation types and levels can be evaluated and compared. The spreadsheet posted above shows in general how the various pieces are calculated and simply added up. No more "I heard this or that from some guy...."
Edited 11/30/2008 4:33 pm ET by DickRussell
So, in conclusion. R-values is R-values irrespective of mass ... under most or normal conditions (although I disagree that it should be most or normal) ... I mean to say conventional or historical conditions (i.e. 'bad' design). I'm not trying to be critical of your design ... I know very little about it; just that good design would take full advantage of mass. Not all designs can do that, but frequently I see designs simply ignoring what I consider thermally obvious.
Again, if you setback your stat any time of the day routinely (e.g. bedtime and/or work), you can save roughly 30% of your energy use (can't recall if that is 30% heating or 30% total). Setback strategy is significant. In mass construction, though it can be a little different sometimes.
Don't know if I would use 45 as your ground temp. Typically 50-55 is the norm, I think. Maybe your area is colder, but I'd think not really. But you did the calc right, there, it looks. You did leave out the affect of air leakage. Even small amounts like 0.10 ACH can result in big energy requirements (relatively speaking). If you mechanically ventilate regularly, you could include that as well.
Bottom line ... the estimated loss roughly correlates reasonably w/ reality. You have a house w/ more consistent insulation than a typical framed house and it probably has an average R-value that may even be better. Your house is also naturally fairly tight (agian relatively speaking). So you have an efficient situation w/out R-50.
Clewless,
A very good summary.
I have measured the ground temperature by sticking a thermometer on the side of the (well) water pressure tank when a lot of water was being used. I think it was higher than the temp I used in that spreadsheet, but we'll let that stand as an allowance for ventilation losses. I was trying to be conservative and make some allowance for the fact that the top four feet or so of dirt will be colder than what's below the frost line at the design temp. Air leakage is not much of an issue.
Maybe what I ought to do is find out why it is that glass insulated houses do not perform as they should. Radiant heat transfer, through the insulation? Bad installation leading to convection transfer?
There is a mass effect in this house, though. I didn't even start heating the upper two floors of the house full time until a week ago. I'll probably shut it down a month before my neighbours can shut theirs down next spring. Spring and fall, I can run a hot fire in the wood stove for three hours and keep the house warm enough for 24 hours if the outside temperature is in the range of 30 to 40. The interior temperature drops very slowly. At the same time it is not easy to overheat this house.
What features of design can you see to take advantage of thermal mass in a house? What is obvious to you that you frequently see ignored?
Ron
A couple of things: 1) in heating … passive solar gain. Often simply rearranging the same window area w/ an emphasis to the south makes a big difference. 2) in cooling, avoiding the east/west and protecting the south w/ a simple overhang/eave to control the summer sun. Designing the form of the building with the long axis E/W.
<!----><!----> <!---->
I realize that such an ideal cannot always be achieved. There is always that view that is contrary to these simple rules. But like I was saying to another guy, you don’t need to always plaster a huge window in front of a great view to get maximum effectiveness. Life is a compromise and I understand that. But I frequently see people irrationally ignoring great opportunities in favor of irrational decisions that provide only marginal benefit.
<!----> <!---->
For example, I now live in the desert. People place large view windows to look at the fabulous view of the mountains to the west. West windows, even small ones result in huge cooling loads. With the generally nice sunny weather here, it seems just as easy to simply walk out onto a well designed patio and enjoy that view in an even better way.
<!----> <!---->
I’m talking about some simple design principles that have shown success for hundreds, even thousands of years. This is architecture 101 here, not some cutting edge new design philosophy. Just take some of the simple basic standards and combine them with our new ideas, materials, and technologies to end up with a design that will provide decades of energy efficient comfort.
The best mass is that which is exposed to allow the ready transfer of energy to/from it. Ultimately it will all work, though. The detailed thermodynamics of mass can get complex fast. It has to do w/ the time/space continuum thing ... just kidding, but it does get complicated.
That's probably a reasonable way to check ground temp. Are you on your own well? City water may be off ground temp if in an elevated reservoir. Hard to say, though.
Glass insulated houses will have higher leakage rates. An in your case with a solid R-18, you may be better insulated than even the average R-21 batt after accounting for the framing. Some of the other posters have hinted that framing area can be significant. I think I've calc'd it conservatively at myabe 20%. Some of these guys were saying even more.
I've seen well built frame houses minimize the framing through 'advanced framing' techniques. Then there is the quality of insulation installation ... near the bottom of the skilled trades where you may often find over and under stuffing of insulation. For the insulation to perform, you need it installed correctly and this is often simply not done. I advocate cutting insulation similar to sheetrock ... +1/4" max. -0. Always cut around obstructions/irregularities ... cut it to fit, don't stuff it.
Then if you seal the house right ... which can be tough to do, you can get a good product. You do have to put out effort to achieve the 0.10 ACH leakage in a frame house. The ICF .... you get consistent insulation and air sealing in one package ... usually costing more, however. Pay your money, take your choice. I've found economics usually follow much of the same laws of thermo.
Is this a pretty small house? I noticed your ceiling and roof area is relatively small and you have a large window area and a large wall area ... relative to your ceiling area. But wait, you said 2,400 sqft of floor area. Do you have your roof/ceiling area right? Multiple floors? Maybe that's it ... two floors ... begins to make sense. Just doing some reality checks ... my nature to go back to the numbers and make sure they look right.
Can I ask what brand of ICF you used?
frenchy.... i normally use a stud factor of 10%... not 20%
and adjust all my wall values for composite wallMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
I disagree that any R value, be it for an element or for a composite structure, is dependendent on a steady state process. We agree that using thermal resistence alone to estimate the response of a system is an inadequate approach. Perception aside, we also agree that the concept of an overall "R-value" to account for mass in a structure is a flawed concept. With the exception of a large temperature swing in a short period of time, steady state analysis of heat transfer through a wall can be respresented faily accuratley. I know that at my house over the last twelve hours, the outside air temperature was 25 degrees, plus or minus 1 degree. Close enough for energy analysis. The effect of the heat that is transferred must take into account the mass of the sink or the source, depending on the process examined.
The "finite element" approcah to modeling a transient heat transfer process through a real substance, using pencil and paper methods is tedious at best, but it can be done. It is an excersie typically experienced in the first year of Thermodynamics. This is why any meaningful analysis is done with appropriate software.
What you are calling a temperature profile, is what I call a temperature gradient.
In classical, pencil and paper heat loss analysis, the following elements would be considered individually to come up with the total: transmission, radiation, perimiter losses, infiltration, and based on the mass a "heat-up" factor is applied. R-value pertains only to the first element.
"Clearly, the overall temperature difference from inside to outside at any instant in time can't be used to calculate an overall wall R value, knowing nothing else." I agree with this, but then why would want to try? It is not a useful exercise, and does not apply to any heat loss or heat gain determination that I have ever experienced.
I feel you are saying two different things in the same argument. On one hand ... long term energy is no better, you say. On the other hand, short term variations benefit energy wise by the affect of mass.
The ONLY times you have a benefit from mass as one ORNL study indicated are days when the outside temp rose above AND fell below your setpoint. Also if you have a passive solar benefit, you can store excess energy in the mass to use later.
This is somewhat simplified as variations in temperatures (inside and out) can complicate things. But we must keep in mind the ultimate laws of thermo. And those laws say you will never have an energy benefit from mass, just because of mass.
Your furnace and inside temp variation will definately respond differently to shor term temp fluctuations ... but in the end ... every Btu that comes out of the mass to stablize interior temp must and will be put back into that mass at some point.
As outside temp varies, Btus flow in/out of the mass ... but really, again in the end, it will be virtually the same as an identical low mass wall when it comes to energy consumed to maintain space temp.
Mass does not somehow majically create Btus for our use (to reduce our furnace output). I'm not arguing that I am against the use of mass. I'm all for it ... in the right context. We should not ... cannot expect to gain a benefit w/ ICF construction without consideration for other design elements (e.g. passive solar).
With all the variations and dampening going on ... The Btus still will need to 'add up'. Eventually my dip in outside temp tonight may not be really seen by the occupants in the mass house ... but at some point, every Btu that was lost during the cold night will have to be returned to the mass.
Tim
R value is badly misused.. a stick framed house has no R value (or nominal) where the studs are yet people say they have R 19 walls.. At best they have R 19 walls for maybe 80% of the wall.
In addition it is extremely easy to mis-install insulation. Where the insulation doesn't cover say the back of an outlet or a wire compresses the insulation away from the wall etc.. A corner isn't filled because the insulation wasn't straightened out etc. . So what starts out in a laboratory as R 19 winds up in the field as an R8. Then too we're dependant on a good wrap job to prevent air infiltration and I'm sure we've all seen houses with flaws in workmanship.
At least with ICF's if the forms are mis-installed the wall fails during the pour.PLus the insulation is continuos Not interupted by studs or other structual members.
Frenchy,
The use of the data by incompetent individuals does not invalidate the data. Your lack of understanding does not either.
The R-value of a composite element must be determined by accepted means of analysis. You do not know how this is done so I understand why you are so confused by these technical details. The frame wall has a composite R-value for the details of construction that apply. Minor imperfections in material production and installation are insignificant, the rest is just mindless babble.
The local building code reflects the mindless bable because that is indeed real world.. unlike the labratory testing insulation companies provide.
Minor imperfections can and do make a significant differance!
Compared to it's size the hole in the Titanic was minor....
You are confusing the published data for an element of a structure and how an appropriate analysis would utilize that piece of data. True, some might state that "I have R-19 walls", but the uninformed statements of some (you make many, BTW) do not negate the fact that a 7-1/2" fiberflass insulation batt installed in a 2x8 wall will provide an average insulation value of R-19. If the installation crew screws-up a corner or two, the overall composite R-value of the wall, taking into accout the effect of the framing, siding, sheathing, drywall, interior and exterior sufaces and the effect of the wind blowing, and infiltration, is unaffected. No one, that knows what they are doing, assumes the construction is perfect. The composite numbers, developed at the begining of a heat loss/gain calculation include some fudge for these issues and the competent designer "knows" how conservative the analysis is and knows where there is or isn't a margine of error to apply when its time to determine the capacity of the required equipment. That is the point I was trying to relay. No one uses published data at face value.
The local building codes and the national building codes for that matter, reflect very little real world and represents only the minum acceptable requirments. They have nothing to do with quality of construction. I have worked directly in the commercial construction business for more than a few years and specifically invloved in how my heating and air conditioning systems integrate in these structures and how and why they do or do not work properly. I go to job sites and examine the details of construction. When a system is not meeting expectations, I examine every detail. Monor imperfections never cause much of a concern. Attention to detail and missed elements, grossly misapplied elements and materials do make a significant difference.
While what you say about the accepted means of analysis is true. However, Frenchy is generally not far off base in that actual practice can and has proven to affect the theoretical values obtained by 'accepted means' in very profound and significant ways. Meticulously installed batt installation can make a significant difference in the heat loss.
Like most things concepts are fine, but the performance is in the details. Just because I'm applying concepts based on 'accepted means' does not give me carte blanc to do poor work and expect good performance.
The reality is, contractors get in a hurry ... especially insulation contractors who tend to be near the bottom rung of the skills ladder.
A hot box test of R-19 insulation is a test of that material only and not a test of an assembly. Typically assemblies are not tested ... as it is difficult to generalize about how the 'typical' assembly of framing members would look like.
The use of R-19 by unskilled people who don't know how to install it DOES invalidate the R-19.
Quite often, it is an assembly that is being tested.
I stand corrected. Normally published assembly R-values, in my experience, are not readily used or available to people like myself that do calculations. With few exceptions, I've always compiled R-values by adding up the components. In a framed wall this may involve adding the components of two areas and then applying a ratio of areas to get an average R-value. The ratio is usually an approximation since it tends to be impractical to account for every square inch of framing in a building.
I was surprised to see the old ASTM hot box test method has been replaced. But I suppose that is fairly normal in that field.
For us field guys ... published R-values are readily available for individual components and we generally use those. An exception might be e.g. RAASTRA block ICF system that submitted a sample for test ... rightly so, since their product is an assembly, not just a component. Interesting that RAASTRA test, if I read it right, tests out at roughly R 7.6 for the assembly.
If you know of a good reference for tested assembly R-value results, I'd love to take a look at it. That would be a great reference to have on occasion.
I think that this has information on assemblies.I copied from an old message and have not looked at it recently.http://www.ornl.gov/sci/roofs+walls/research/detailed_papers/Whole_Wall_Therm/index.htmlhttp://www.ornl.gov/sci/roofs+walls/tour/LSCS.html(Large Scale Climate Simulator).
William the Geezer, the sequel to Billy the Kid - Shoe
Generally good stuff. I'm disappointed at the technical writing and the lack of detail on the descriptions (didn't they distinguish between standard and advanced framing?). For something that was intended for the more lay reader, it wasn't very well compiled (referring to the paper on wall R-values).
Seems the other article was focused only on roof assembly testing ... and no results. The ASTM C236 test method has been around a long time. There is generally little impetus to test complete assemblies.
Also, the article on walls implies that there were some testing/analysis related to mass construction that simply wasn't done (or at least presented in the paper).
The lack of detailed descriptions of the wall constructions leaves me with little practical information about what I might use. Certainly better than nothing, but I'd feel a little like I was working in the dark a bit by choosing a particular wall section.
I guess I'd expect more from ORNL. They have a strong reputation. I'll probably make some comments to the authors about their publication.
"However, Frenchy is generally not far off base .."
I have discussed many technical issues with him over the years. My assessment differs from yours. Maybe its the language barrier.
This form of communication when getting involved w/ these kinds of discussion can really hinder the 'understanding factor' (which I think the ASHRAE value is maybe 0.36 if I recall ... just kidding). It's easy to go off on a tangent or think someone meant this when they really were referring to something else.
I may have missed your point some how some where. I either didn't listen well or you didn't speak language that I would understand ... takes a lot of both to 'get it'.
Not quite the same as talking face to face ... the future internet communication!
And those are VERY good points. You've maintained a good perspective ... which is needed in these kinds of discussions.
What you are talking about is called "effective" R-value and it is for any high mass structures.It is based on daily temperature changes. A lot of what you see in manufactures ads is blowing smoke.But there have been some studies that qualify it.I have seen numbers like 30% improvements for areas like the desert SW where you have hot days and cool nights.And maybe 5% in someplace like Atlanta.And the amount varies by the type of mass and where it is located in the structure vs other insulation. The IRC has a table of altenate minimum values of insulate for high mass structures..
William the Geezer, the sequel to Billy the Kid - Shoe
I am in a similar situation with ICF walls and a SIP roof. I would be satisfied to know how much fuel is used for heating. The complication is that the same boiler is used for hydronic floors as domestic hot water. Then there is the wood stove variable…
CJD
Like me, you have too many variables to use fuel consumption as an indicator. Unless- you could quit using hot water and burning wood for a while. Just a couple of weeks should give you enough data. It's a small price to pay for the truth.
Ron
Hello Ron,
I'm in the same situation.. compounded by my 76 windows, three entrance doors, and three garage doors. I suppose the portion of the house was cantalevered over the lower structure also changes the calculations..
I'm not sure R value is of any real value.
Isn't the reason for getting good insulation to reduce the cost of the use of energy and R Value is simply a shortcut to those numbers?
So perhaps what we could do is skip all the calculation and do some accounting instead?
Thus if we know how many degree days are involved (something I find on my gas bill) and know the interior size and efficency of the furnace then we have some idea of the cost of heating..
While that number is going to be somewhat soft due to claimed efficencies and actual efficencies varitations plus other inaccuracies in measurement..
frenchy,
Your accounting approach is just what Dick Russell suggested and it might be the best way to solve this. Maybe even the only way, though I had some hope of being able to figure out the heat loss over a short period of time from the temperature drop.
What I want to end up with is a realistic R-value for ICF walls in order to communicate that to customers. Right now, what I have is manufacturers' figures with no idea where that came from or what kind of house that might apply to. Design is such a large component of energy efficiency. I want to be able to say, "In this particular house, the ICF walls perform as if this was a wood frame house with R38 glass insulation in it" or whatever the numbers indicate. I want some real information I can prove.
Ron
The R-value of the walls is what it is. What you are trying to measure is not the R-value of the walls, rather the heat loss of the whole envelope, which you could do with a record of the heating degree days and the BTU generation of all your heating appliances for a given time period. But as others have said there are so many variables it's a meaningless number in relation to the actual r-value of the walls.The foam guys are always saying that 4" of foam, while technically r-28 is really a much higher r-value. No, it's r-28. R-value is a very specific measurement of conductive heat-loss through a material. It is what it is.It's the overall air-tightness and the reduction of thermal bridging that are inherent in SIP construction and sprayed-in foam methods that increase the performance of the envelope. You can't realistically boil the whole picture down to "this house is insulated to R-xx". Steve
mmoogie,
I should have been more careful in stating my objective. What I want to figure out is what is the equivalent in conventional wood framing and batt insulation of what I have here.
In order to do that, I should have said I was aiming for a number to attach to an ICF wall comparable to R-value in order to be able to spec an equivalent construction.
I do know that this house performs better - loses less heat - than its calculated heat loss using R-values would indicate. so something about that kind of calculation is not strictly applicable to this house.
Ron
Ron,I think I understand your objective, but I don't think you will be able to get any kind of meaningful equivalent. You don't have a meaningful control house to compare it to. If you were to build a twin house right next door, in traditional frame construction, oriented in the same direction with the same external exposure to sun and wind, and heat both houses under the same conditions to the same temperature over the same time period with the same number of people living in approximately the same manner, you would have a meaningful basis for comparison.I think you are placing too much weight on wall-assembly to wall-assembly comparison.ORNL has tested various wall assemblies for actual whole-wall R-value performance. But there are many other factors besides the effective r-value of the walls of house that affect energy consumption. Effective whole-wall r-value numbers just don't tell you that much. Of equal importance is the air-tightness of the structure and the efficiency of the heating plant. Those metrics can vary immensely depending on the details of construction.I do think you could quantify the energy consumption of your particular house and articulate the value of that performance to potential clients, I just don't think saying " this house is the same as a frame and fiberglass house with wall a foot thick, and that would cost 25% more to build" means anything. I thinks it' would be far more meaningful to say something like "because of the better insulative value and superior air-tightness of SIP construction, you will use "x" percent less energy than a conventionally-framed and insulated house".The real question is how do quantify how much better it is without a meaningful control house to measure?Steve
Edited 11/23/2008 10:26 pm by mmoogie
Hi,
The ORNL study of ICFs and another study that tried to determine if the ICF offers a higher R value than you would get by just adding up the R value of the foam form. The 2nd study, which was a pretty careful study on an actual building with heat flow measurements concluded that that the R value of the ICF is just the R value of the ICF foam form -- they did not see a higher effective R value from the ICF mass.http://www.builditsolar.com/Projects/SolarHomes/constructionps.htm#ICFGary
I can accept that however air flow through a stick framed wall is a real issue. That's why we use wraps etc.. wraps can and do fail over time..
So air flow would be nigh unto impossible thru a concrete wall. thus stick framed starts off with a disadavantage over ICF's.
That also ignores other factors such as durability and sound transmission. Plus safety. Frankly in the case of a drive by shooting which would you rather be behind? Concrete or 3 1/2 inches of fiberglas insulation?
Finally the study in question made several assumptions which are not based on maximising the performance of ICF's Noteably along the lines of solar gain from the use of ICF's
GaryGary,
That can only make me sure there is more to keeping the heat in than R-value.
Ron
Do it small scale then.. eliminate all the variables such as windows doors etc.. Take a tiny room made with ICF's and heat it to say 70 degrees then seal the room completely and record the temp drift on a cold night then repeat with stick framed and finally with SIP's for a full comparison on the same night.
I'm sure this magazine would be interested in such an article and perhaps help you underwrite the costs involved.
I understand the desire to be accurate. Everything I had prior to my making up my mind was anecdotal or manufactures statements or data. However that data would vary greatly due the the variables of weather and location..
For example If I said in all sincerity that my house costs me less than 20% of what my old house costs to heat/cool that still doesn't say that ICF's/SIP's are that much more efficent.. So the long term savings aren't 80% of my old home. If annual heating cooling costs of my old home was $2650 and my new home is about $550 that still doesn't reflect the inevitable increase and inflationary pressures of future energy costs.. So I save more than $2100 a year for the next 100 years. I save 2100 x inflationary costs of energy x 100 years..
Now some might have issues with that 100 year period since the currant age of an american home is 56 years. however the durability of concrete structures compared to wood structures is well documented.. and a period of 100 years shouldn't be out of line.. (which brings up another value of ICF's over stick framed) one that is measurable and quantifiable..
At a minimum you avoid the need for extensive termite and insect protection as well as normal deterioration due to rot caused by moisture damage..
frenchy,
I'm not looking so much for information on ICF's in general, but for provable data on this particular house. Once I have that, I can calculate what it would cost to build the equivalent house in wood frame construction.
I'm willing to bet that wood would cost more.
That's a good idea about proposing FHB do a piece on this. I'll send them a note. (They recently bought a short piece from me on FabForm footing construction, which I first discussed here.)
Ron
"Take a tiny room made with ICF's and heat it to say 70 degrees then seal the room completely and record the temp drift on a cold night then repeat with stick framed and finally with SIP's for a full comparison on the same night."That is not only a measure of insulation value, but also of the thermal mass of the structure and it would not accurately reflect the relatively cost of heating them..
William the Geezer, the sequel to Billy the Kid - Shoe
"What I want to end up with is a realistic R-value for ICF walls in order to communicate that to customers"
You can't get a realistic R-value for the ICF walls alone on an as-built from any accounting method. Averages of fuel consumption/Ft² in a number of similar homes in your area over a year would probably be a better marketing tool anyway. ICF does not matter if you don't seal everything well, use leaky windows and doors, have minimal roof insulation, or leave windows open. You will also find that ICF performance is more sensitive to passive solar design than low-mass structures. You can't compare ICFs in Juno to Phoenix.I was able to turn heat off months earlier and turn it on months later than my stick-built neighbors due to a lucky balance between insulation, infiltration, solar gain, and thermal mass.
CJD
I think you can get a realistic "equivalent to R" or "performs like R" value for a specific job from accounting, but generally speaking, I think you are right.
What I want is a realistic value for this house here, not a value that will necessarily have any relevance beyond these walls, except that I can use it to estimate the cost of a wood house like this house that will consume the same amount of energy.
This afternoon, I calculated the amount of heat that would have to be taken from the air contained in the house in order to drop its temperature by the amount that I observed. It was about enough heat to make a good pot of tea and far less than heat losses should have been through the windows alone. So heat is being lost by everything in the house as the indoor temperature drops and the method I originally had some hope for simply will not work. Too many elements involved.
Ron
Yeah, most of the heat required to raise the temperature of a house (over and above losses through the walls, etc) goes to heating the walls (drywall makes a great heatsink), furniture, etc. Heating the air is trivial in comparison.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
You've hit part of the nail on the head with your calc of how much heat the cooling of just the air inside the house gives up. To give a couple of numbers to quantify how much heat the walls, floors, and furnishings provide, the approximate heat capacities of wood, gypsum, and concrete are:
wood 0.33 BTU/lb/deg F
gypsum 0.26
concrete 0.21Odd that concrete has a lower heat capacity, but it is far more dense, so BTU/cu.ft./deg F would be much greater.Anyway, if you add up the parts: weight of wall frames, flooring, wood anything times 0.33, plus weight of GWB covering the walls times 0.26, you get approximately the amount of heat given up by the house's innerds per hour per degree F. Yeah, a lot more than the air gives, since it all weighs far more.The other part of the difficulty of calculating wall R over a short time is what I said before, that the house is never at steady state with respect to temperature. Consider what happens when you go away for a week in winter, leaving the T-stat at maybe 55 to save fuel. On return, your heating system cycles on/off frequently at first, as it dumps in heat, the heat is slowly absorbed into the walls and floors, and the system kicks back on. After some hours of this, the cycling is less frequent. The walls and floors provide a lot damping effect on the shots of heat, absorbing it more slowly than the system injects it.To put some numbers to the ICF wall issue, and help explain the claims that the wall is "like R-50," consider a wall with R10 of EPS foam inside and out, with 8" of concrete sandwiched inside. The 8" of concrete, at R=0.08/inch (the number I most often see), that's a total of R 0.64 for the concrete, or 3% of the total R of the wall. At steady state, with 70 F inside and zero outside, the temperature drop across the concrete is a whopping 2 degrees.Working on a per square foot basis now, the 8" of concrete, at 145 lb/cu.ft. and heat capacity of 0.21, holds 20.3 BTU of heat per degree F. Since the temperature drop across the foam layer on either side of the concrete is half of the other 68 degrees, or 34 degrees, the rate of heat flow across it is delta T/R or 34/10 = 3.4 BTU/hr/sqft. Since, at steady state, no net heat is accumulating in the wall, the same rate of heat is lost from concrete to outside as is gained coming to it from inside the house.Now suppose we drop the outside temperature by X degrees. Ignoring the heat capacity of the foam layer (being light compared to the concrete), the imbalance in heat flow is X/R10. If the temperature drop is, say, 15 F, the imbalance is 15/10 = 1.5 BTU/hr. Since that square foot of concrete holds 20.3 BTU/degree, it starts to cool by 1.5/20.3 = 0.074 degree/hour. That's over 13 hours to cool by just one degree.Sure, the concrete has little R value, but considering how little heat passes through the two foam layers, it takes a long time for its temperature to respond to a sizable change in temperature on either side.I think it was one of those ORNL reports referred to elsewhere in this thread that modeling of mass-heavy walls insulated in different ways (inside/outside/middle/combinations) was done for various climates. Not surprisingly, the most effective situation was where the outside temperature swung to either side of the maintained inside temperature, and where the heavy mass was in direct contact with the inside air. Least effective is where the outside temperature is constantly colder or warmer than inside and does not undergo large swings over a 24-hour period.For a cold climate, an ICF wall won't do much more insulation-wise than the foam on either side of it when the outside temperature is cold and constant. On the other hand, when the outside temp goes from somewhat cold to an overnight bitter cold and back up at daybreak, that thermal mass will damp the temperature swings somewhat, shaving the peaks.I guess I ought to end this long-windedness with some kind of bottom line assertion for others to agree or disagree with. I suppose I'm claiming that considering the large mass of house within the exterior envelope and the large mass within the ICF walls, temperatures will change so slowly and unevenly that trying any measurement of heat loss over a period of a few hours or even a day will be very inaccurate. I would imagine the inaccuracy would be worse than just taking the measured R value of EPS foam times the thickness.
DickRussell,
OK, I'm convinced. The annual accounting approach seems to be about the only way to do this.
I should have realized it myself. I spend a lot of time telling people that one of the big advantages of high mass is the lag it introduces into the response time of the house to changes outdoors.
I've read the Oak Ridge report you referred to. I concluded from that that even in a cold climate, ICF construction makes a lot of sense in that such construction can extend the no-heating season in both spring and fall.
The ORNL concluded that foam outside, concrete inside was the best configuration for heat retention. It isn't the best for hanging pictures though. On the other hand, once you got one hung up, it wouldn't be fallin down very soon.
Ron
My 2 cents worth, I have worked on ICF an SIP buildings. in a Sip building the performance depends on the design and ability to make it tight. the 2 1/2 storry house we did required 2 x 10 wall studs between panels and king studs and trimmers at doors and windows. I could visualize an infra red photo showing cold spots in the walls like when you can see where the roof trusses or wall studs on a frosty day. We used 2 1/2 times as much panel sealer and spray foam as the vendor recommended. I was on crutches and when they set up the scaffolding and I was watching the roof go on I could see gaps between the foam when the osb was pulled tight. End of panel calking is not the best way to seal panels. When there was 3 inches of fresh snow on a concrete floor over 4 inches of foam you can see where the16 inch thick footings are. the snow melts faster in that area. The ground heat transfers up thru the concrete. one advantage of ICF's is the ground heat can traansfer. If you do a good job of vibrating your concrete on an ICF you will have consistant tight walls. with no air leaks. Some one is building a 6000 sq ft ICF house about 5 miles away and has a terrible roof truss design Only 6 inches of space for insulation around the outside walls. THe ICF will probably be blamed for poor performance. My son is an electrical contractor and did the work on a house featured on TV as energy efficient. It had Sip panels for the roof with recessed can lights. HIs comment was what are they thinking. all those places with only an inch or 2 of insulation left. you will probably see the snow melt patern a dozen places on the roof.
Good points I especially like what you said about conducting ground heat up a ICF wall!
I hadn't thought of that.. You would appreciate the details I took when I built my house at the roof wall juncture using SIP's I ended the foam on the foam (possible to do with a 27/12 pitch roof) and used one common 2x member rather than 2
In addition before setting my panels in place I used sprayed foam as a sealant and then quickly closed the space between and nailed it while the foam was exanding.. rather than the glue they would have had me use. I saw that in cold weather it simply couldn't flow out and provide a good seal..
I also used the weight of the panel to seal the joints of the panel rather than attempting to clamp them together.(Put them in horizontal rather than vertical)
IT paid off.. this house is 5500 sq.ft compared to the old one at 2500 sq.ft. plus this place has 76 windows compared to less than a third of that with the old place.. I'm using the same furnace (recycled it) and my heating bills are $300 a month lower. Plus summer cooling is down to under 24 hours total in spite of temps well into the 90's with 100% humidity.. during the summer. On an 80 degree day I can actaully get chilled
I got married last summer and have busy working on my wife's farm. She had a duplex lot with sewer connected and permits to build. They had planned on using SIPs that were designed with no studs between panels but the next county south of us changed their requirements to require a post and beam framefork for sips. so we are going with 2 x 6 walls and spray foam insulation. not as energy efficient but we have to meet costs bugeted. She has a farm lot already subdivided into 10 lots and we are thinking of building starter homes and will probably use Quad lock Icf's. I worked on one a couple of years ago and like their products.
I ran headlong into that objection too, if you get a copy of the building code or what the building code is based on you can do it even over building officals objections.. All the SIP panels I know of meet all building codes and once something meets the codes the issue is moot..
Next you can build a post and beam home very affordably. Sawmills sell the heart centers of timbers for $20.00 each.. That's the nation wide price. You see hardwood heart centers that are 9"x7" x 102+ inches are what railroad ties are made of.. they can be made from any structually sound hardwood and the price of $20.00 each is the standard price paid for them..
So a bent for a room with 10ft ceilings will cost you only $100. That's an 8 foot spacing. With post and beam you don't need to be carefull and do mortice and tenion work you can simply lag bolt everything together. Thus a room that is 18'x18' would only cost you about $500 to do. You could assemble and install the whole thing in less than a day. Smaller rooms would be even cheaper.
Think of how much more attractive your house will be with a few thousand dollars worth of timbers in it..
Wow! That's one of the best explanations that I've read in a long time. I was getting a bit glazed-over by some of the math, but I got the gist of your calculations. Very interesting and thanks for taking the time to put it down so concisely. Are you, or have you, built an energy-efficient home yourself? I'd be really interested to see where you found the best "bang for your buck" came from, if you did. Thanks again.Cheers,
KenYou live and learn. At any rate, you live.
If you heat with gas and you have your utility bills for the last year, you can calculate the real heat loss based on this information:
http://www.cmhc-schl.gc.ca/en/co/renoho/refash/refash_018.cfm
In my case, I assumed that the gas consumption during the summer was for the water heater so i subtracted that amount from all my monthly readings.
Edited 11/23/2008 2:41 pm ET by Chucky
There is an alternative approach: On a reasonably cloudy, windless day heat the house up to, say, 80F, then time how long it takes to get down to, say, 70F. Next, record your gas meter reading (don't know how you'd do this for oil or propane) and heat the house back up to 80.
Calculate how much gas it took to heat up, divide that by the hours it took to cool down plus the time it took to reheat, and you have energy per hour.
The next thing you have to do is factor in the outdoor temperature to calculate energy per degree-hour. Take the average of the high and low inside temps (ie, 75 in the above example) and subtract the outside temp from that (average readings taken several times during the test). Divide that temp difference into the energy per hour and you have energy per degree-hour.
DanH
That sounds like a good idea that would result in a useful number.
I might be able to do that even though I have an oil burner. I could record the amount of time the burner is running perhaps by using a microphone at the burner fed into the computer and recording onto a sound recording program. Then, delete the portion of the recording under a certain sound level and what's left is burner time.
Oil consumption per unit run time is fixed.
This year, I haven't yet begun to heat the upper two floors of this house with the oil burner, so I'd have to let it run for a day or so to approach a steady state.
I'm going looking for a microphone.
Thanks,
Ron
"Oil consumption per unit run time is fixed."Note that for some of the high eff modulation burners that is not true. Don't even know if do that in oil or not.And I don't see any reason to cycle the tempature as Dan suggested.Just pick a day with little wind and sun and meausre fuel consumed for a period of time, say 10 am to 2 pm and at an average OAT.This would be easy with NG. Just put the WH on vacation setting during time and not use any gas stoves or driers.But R-value is based on sq ft of surface area so you probably need up with averaging in the walls and ceiling. And depending on how much work that you can do also average in the windows.Don't know if you can any numbers that are meaningfully compared to advertised R-values. There are assembly values that have been published by Oak ridge. But that is not what people see or understand.May I suggest a who other idea.See if you can get some date on similar size houses. don't need to be identical, but similar size and number of floors and the built around the same time.Then get the fuel usage in gals for a fixed period of time and then convert them to gals/1000 sq ft.That would be a real number that people can understand..
William the Geezer, the sequel to Billy the Kid - Shoe
Bill,
Taking advice from people who contributed to this discussion, who thought an annual approach was the only one that made sense, I added up my heat inputs for last year (wood and oil), allowing for efficiencies, and found a source for the degree days for that heating season.
I calculated that the actual heat consumption of this house was essentially identical to the heat loss calculated from the plans pre-construction.
Given all the factors in play in a real house, like coming and going through doors, the effect of wind, radiant gains and losses, input from cooking and so on, that's an astonishing coincidence.
(With the Toyotomi boiler I have, not a mod con, oil consumption is fixed per unit time.)
Ron
OK, now my 2 cents; maybe lend a new perspective ... Started reading this this a.m, but had to go to work.
The "effective R-value" argument is largely bunk. I can appreciate trying to simplify and to make comparisons. But it really isn't fair and it is just the lazy sales persons way of justifying a product.
R-value is just that ... as several have stated. Why are you trying to compare R-values when there is more than conductive loss that is at work? As someone pointed out, ICF often means reduced air leakage ... so why don't you do a blower door test and compare it ... with what? Another poster mentioned that you have no comparison structure to compare with. BUT if you do a blower door and find that you are at say 0.10, you can reasonably say that you are far lower than the 'competition' at say 0.35.
I believe I've read parts of an ORNL study related to this topic (it may be in the website posted in msg 19). I did this in response to someone trying to sell me that log houses use less energy because of the thermal mass. Again, BUNK! The study looked at two identical structures (mass and frame). The study concluded the mass was superior in energy performance ... WHEN the outside air temp both rose above AND fell below the setpoint (stat) each day. What a revelation that was (sarcastic). Good study, but it told us what we [should] already know.
Another time mass will be of benefit is whenever there is 'free' heat (I'm not talking about your wood stove) ... as indicated in message #11 ... when you have a building DESIGNED properly to take advantage of solar energy.
You can't simply say you have an 'effective R-value' because of the superiority of one element (air leakage) that has nothing to do w/ R-value.
You can determine your heat loss ... throughout the year. Do like message #7 ... eliminate the summer energy use for DHW for 12 months, add in your wood heat value and you have total heat loss in Btu for a given year. That's about it. You can convert it into effective net R-value for the whole house, but that is meaningless and not useful for any other comparisons.
You can't use the timed temperature drop approach in message #12 ... because you are measuring air temp only and the thermodynamics of the mass over a short period of time cannot really be accounted for ... THAT is a complex topic, but the principles are simple.
Assuming normal design and [mis]oirientation of a house ... R-value is R-value. Period. And so is air leakage. They are separate. The existence of mass in and of itself will virtually do little to nothing for your energy bills. It will take the same amount of BTUs to heat as an equivalent frame construction (at the same air leakage) ... unless you have a source of free heat (e.g. sun).
My guess is that a SIP construction will outperform a ICF construction assuming reasonable measures taken to seal the panels (given a house w/ no solar benefit). Better R-value and equal air leakage. Concrete is heavy ... and an expensive material. Not without it's very nice benefits. SIP is expensive because of the 'high tech' material (foam plastic).
Pay your money, take your choice. You always have to live with the laws of thermodaynamics. You can't create energy just by having thermal mass. I'm just trying to make sure you maintain proper perspective when you go to sell an idea. I'm not trying to push one idea over another ... I've no agenda there. I appreciate all types of construction.
I get tired of sales people saying how their construction is 'effective' R-50 ... some don't even say 'effective'. Sell it, but sell it right. Don't try to make an R-15 wall something that it isn't. Remember also ICF insulates BOTH SIDES of the mass, not just one side as was noted by the poster that referred to the ORNL study.
Edited 11/24/2008 9:58 pm ET by Clewless1
Also ... if you calculate all your annual energy use for the entire house, I can give you a general idea of 'how you're doing' ... like gas mileage for houses. Need your floor area, too.
clewless1
I'm starting to think that I'd rather listen and learn more about thermodynamics in general than drop into specifics, but.........
(You use English units, right?)
Last year, we burned 600 litres of fuel oil at 90% efficiency and about 1.5 cords of mixed maple, birch and some spruce at maybe 50% efficiency for a total of about 40,000,000 btu used in the house. I'm guessing at the amount of wood. There are other heat inputs - waste heat from an electric water heater, cooking, body heat, solar gain. I can't quantify them, but they are significant contributors.
For the whole heating season, there were 5525 degree days at a 60F balance point ( http://www.weatherdatadepot.com/index.asp This is the only place to look for weather data)
At the design stage, I calculated a heat loss of 27,000/btu/hr at a design temperature of 5F. I thought that was unbelievably low. Then, in the last stages of construction, in December 2005, I heated the house with a sheet metal wood stove I use inside a tent. I've been cold in the tent with the fire going hot, but it was enough for the house.
The floor area inside the house walls is 2400sf. The floor area inside the tent is 80sf.
Ron
Need your electrcal consumption, too. Talking about total energy here.
Litres ... will convert to gallons.
Edited 11/26/2008 9:16 pm ET by Clewless1
Clewless,
I've coverted those litres into gallons and discounted for inefficiency. That 40,000,000 btu is the house's heat loss, more or less.
Electricity consumption? Is there some way to estimate how much of that is converted to heat? I'll get that this evening.
I gues everything is heat in the end, isn't it?
Ron
Essentially all of the electrical usage, save for outdoor lighting, outside hot tub, etc, is converted to heat.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
40,000,000 plus the combustion loss? It's important to not discount the energy consumed ... All of it.
Thanks for the HDD ... almost identical to what I'm used to using, so the weather factor will be similar. I'm used to base 65, though; I was a little surprised to see you quote the 60 degF ... that is not historically, the standard.
the 5 degF design temp sounds about right. Spokane, WA is 6835 HDD @ 65 base and their design temp if I recall is 4 deg (maybe it was -4 deg, memory is fading).
Your 27,000 Btuh for calc'd heat loss ... 70 deg inside? Does that include infiltration/ventilation? Or is it just the conductive loss throught the surfaces of the envelope?
KWH convert to Btus, energy is energy whether electric or combustion or whatever.
You can calc annual energy using HDD ... but there are some factors ... e.g. night setback that can alter that ... but you can also recalc HDD to account for that kind of thing. Simple concepts ... but complications pile up quickly.
clewless
Your 27,000 Btuh for calc'd heat loss ... 70 deg inside? Does that include infiltration/ventilation? Or is it just the conductive loss throught the surfaces of the envelope?
That's conductive loss and ventilation. I made no allowance for infiltration or any radiant factors. 70F interior temperature. I can't find the calculation any more. It's been years. Perhaps I'll just do it over tonight.
60F seems like a reasonable base for calculating HDD. I would never think about turning on the heating plant if the exterior temp was as warm as 60.
Ron
clewless,
Forgot - one year's electricity - 8800kwh - mostly going for hot water
Ron
And I forgot -- hot water that goes down the drain doesn't count. But I doubt if "most" of the amount is hot water.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
however some of that heat from the hot water goes down the drain while some is lost to heating the house..
plus water introduced into the house provides an additional chilling factor and as a result heat is lost up the vent or down the drain..
Roughly, you are at ab out 35,000 Btu/sqft/yr. For a new, well built house, that is fine. I know nothing about your lifestyle, but on average you are doing well. Residences range from 20,000 to 120,000 depending on the age of the house and the lifestyles. Reasonably built houses of the last 20-30 yrs. I'd expect around the 20-50,000 Btu/sqft value. I haven't calc'd my new house, yet. Only been in it a few months. Considering your house is probably 'tight', you are about average.
BTW, your electric use is about 37% of your total energy use ... hot water, lights, refrigerator, cooking?, and that computer you are staring at. :)
An semi-educated guess is that your air leakage might be around 0.10, but all I know is that you have the ICF construction, so that has to be taken w/ a grain of salt. Tested frame houses can be expected to be 0.35 and up if sealing is reasonably done.
Hope all this is food for thought. Enjoy, dude.
body heat? Yeah ... but not significant, really. 6 people in a house and say a load of 30,000 Btuh ... that is only 5% of that load. 250 Btuh typical of people. And that is a fairly small load, really for a house. Commercial buildings are a little different. Higher density of people (often).
Cooking? Only if you do it a lot. Lights ... pretty tiny in a residence. Solar? I didn't think you had solar in Nova Scotia! :)
Solar only if you actually get solar, and it's winter, and your house is designed for it (i.e. south facing windows). Solar can be significant. I built an unheated passive solar sunspace on my house in a northern climate ... IF it was very cold out and sunny ... it would get up to 90 deg in that space! In 5-6 hours of winter sunny day you can gain a lot of energy.
Looked at your weather site ... interesting that HDD are on base 60 deg and CDD the same ... I tend to disagree w/ a CDD base that is that low ... mainly because between 60 and say 75 ... if it gets too warm most people will simply open windows, not turn on the A/C. In commercial applications, you over ventilate (economizer or free cooling) during those temps. Seems that relevant cooling data is really above the stat setpoint (or slightly lower), not the balance pt temp of the building.
I've never seen HDD routinely expressed on the base 60 ... always on 65 (old ASHRAE standards for calcs).
ron... thanks for the weatherdatadpot linkMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
i spent the 50 bucks and downloaded the hvac computer software (homeowner version). you plug in your house data and it tells you heating and cooling loads.
the program saved me a lot of money in not buying extra capacity (to be on the safe side), and so far i have no complaints at all...at least i have plenty of heat and cooling. hvaccomputer.com if i remember right or google "hvac calc" spend the time making sure you are entering everything accurately -- it's well worth it IMO.
You will find out if your fine tuning of the design and equipment selection is OK ... WHEN you approach design conditions (e.g. -10 degF or whatever your design temp is). The VAST MAJORITY of time, systems run at 1/2 of their peak capacity because that is where the average outdoor conditions are. I used to size systems where the design temp was about 4 degF ... but average winter temps at the same location were 34 degF ... roughly half the load!
Your approach is exactly what I advocate ... assuming there is a little tolerance for a worst case scenario. That is in the case above, WHEN it drops to -10 degF, will I tolerate my space temp not being reached? In hospitals, that is not the case. In most houses, the occupants might tolerate a lilttle.
If you don't calc your load reasonably accurately, you stand to grossly oversize your system even at peak conditions ... which at average conditions will be horribly oversized. A theoretical ideal I think would be to have a furnace capacity that adjusted itself for the load and ran continuously ... just meeting the load.
I'm not going to read through all 125 posts on this thread, but there's a simple answer to your quest: it's already been tested.
A Canadian study of an ICF apartment building compared to a similar wood-frame building showed:
"The ICF wall assembly studied in this research project had an insulating value that was fairly close to the nominal insulation value of the polystyrene layers of insulation. No thermal mass impact or higher effective insulation value was observed. However, the air leakage testing found the building to be relatively airtight and this can, for the most part, be attributed to the ICF wall system. Additionally, the ICF wall system provided a significant thermal buffer between indoor and outdoor conditions, which would provide for enhanced comfort conditions within the building."
https://www03.cmhc-schl.gc.ca/b2c/b2c/init.do?language=en&shop=Z01EN&areaID=0000000127&productID=00000001270000000041
Another study performed by NAHB Research Center for HUD on three identical side-by-side homes, one ICF block, one ICF plank, one 2x4 construction showed:
http://www.pathnet.org/sp.asp?id=1005
Solar & Super-Insulated Healthy Homes