Super Insulation and Natural Convection
I’m going to be building a super insulated, three story ICF home with an open central staircase.
I’m curious about how natural convection will work in such a structure, depending on where the heat source is placed.
For example: how will convection occur if there’s a wood stove on the top floor? How will the surface temperature of the walls change the air flow? Will warmer outside walls help air flow?
How will convection occur if the wood stove in on the bottom floor?
In either case, how can convection be improved?
BTW, I don’t plan on using a wood stove as the primary heat source but I’d like to be able to count on it for whole house heating, in the event that it’s needed. And I’d also like to be able to cut the heat bill in half, burning wood in an efficient stove.
Another question; assuming that the wood stove will be used continuously to help heat the home, will radiant floor be as effective as hot water baseboard? How will the two differ?
Edited 3/5/2008 8:35 am by Hudson Valley Carpenter
Replies
I wouldn't consider an ICF house to be superinsulated, but it would certainly be well insulated and should be very air-tight. The thermal mass will add some effective R-value, but this diminishes in a cold climate.
A very tight, well-insulated house has very little natural heat stratification and little natural convection. What helps wood stove convection in a poorly-insulated house is the cold air wash falling off exterior walls and windows which is much denser than the heated air from the woodstove.
A three-storey house will be more difficult to heat with a non-distributive heat supply such as a woodstove, unless you assist the distribution with fans and ductwork.
Placing the woodstove on the lowest floor will aid natural convection as long as there is both a warm air supply path (such as open staircase) and a return path.
The more open the floor plan, the better the heat distribution on each floor, but moving heat from floor to floor requires a circuit.
If you're running the woodstove regularly, then a radiant floor system will not cycle often enough to keep the floor warm and you will loose the advantage of the "warm toes". It would make more sense to use a quick-response backup heating system such as hydronic baseboard which can pick up the slack as soon as the woodstove dies down.
Solar & Super-Insulated Healthy Homes
Excellent answers, thanks.
You've confirmed several theories I've been contemplating, most significantly the need for power assisted returns, even with an open central staircase.
I'd heard at an RF seminar, going back twenty years or so, that RF lags enough so that it's not really compatible with other types of heat. Therefor it would seem that, if someone has their mind set on both RF and wood, a wood fired boiler would be the best way to go.
BTW, The ICF system I'm currently planning to use http://www.quadlock.com has three options for foam thickness, R-40 being the highest advertised value.
According to the Quad-Lock product manual, the R-values range from 16 to 34.
But an R-34 ICF wall will offer more than that in effective R-value because of the thermal mass.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
HVC
Just bumping this thread for Mike Smith.
Rich
Thanks for the bump. I'd forgotten this question. My intention to use ICFs for the first time has since changed due to real world costs but I'd still like to hear ideas about heating a super insulated three story home.
Since participating in another very active thread on super insulated designs, one where Mike Smith generously offered a lot of insights and ideas, my plans are to stick build in the same configuration I wrote about in my first post here, using deeper Mooney walls to enhance the R-value.
HVC
The house you described originally sounds a lot like my house. I have a three-storey ICF house with radiant HW heat on the bottom two levels and a wood stove on the middle level.
I spent a lot of time in the design stage trying worrying about the heating system, its controls, compensating for fast heat inputs like the wood stove or even the effect of baking a load of bread (which I do) or the sun coming out. I was getting a lot of advice from salesmen, too, who all thought I needed more and more and more - equipment, controls, this and that.
I bought the heating system from the guy who said, "You don't need any of that. You need an area of the house where the heating system can respond as fast as the inputs change." So we installed HW baseboard convectors on the top floor, where most of the heat loss occurs anyway. He was right.
I am also very happy that I stuck with ICF, despite some cost pressure. It isn't just about heat, either. The difference between this and a wood house is fundamental. It is not about details and it's not about design. This house feels different, sounds different from a wooden house. It's as solid as rock and, when you're in it in a storm, you know that. It's as sheltering as a cave.
Ron
Thanks Ron, I appreciate hearing from those who live in their own designs, homes that they planned and built carefully which work as well or better in real life than they expected.
Of course I'd like to experiment with ICFs but my primary aim is to build a very energy efficient home which fits a particular market and will produce maximum profit.
My retirement plan is to use the capital gains exclusion on the sale of one's primary residence as a serious income enhancement, building new and selling every few years or as required.
"I am also very happy that I stuck with ICF, despite some cost pressure. It isn't just about heat, either. The difference between this and a wood house is fundamental. It is not about details and it's not about design. This house feels different, sounds different from a wooden house. It's as solid as rock and, when you're in it in a storm, you know that. It's as sheltering as a cave."
The difference is not as "fundamental" as you suggest. My modified Larsen Truss homes feel just as you describe and are almost certainly more energy efficient. Without a doubt far more resource efficient.
Contrary to your assertion, it IS about details and design as well as material choices and quality of workmanship.
Side-by side house analyses performed by NAHB Research Center and CMHC (Canada) has demonstrated that an ICF house is no more tight or energy efficient than a wood-frame house.
CMHC: "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"
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Hi I would like to see the study. I live in a three storey ICF in Sask with in floor heat from hot water. I would do it again or do straw bale but stick framing I think is a dianosaur.
in 83 I built a Modifed SRC wall, 12 inches fiberglass curtian wall etc. Im sure there is a current name for it. It was a very warn and comfy home in a wood basement. Sorry I sold it I was cheap to heat and sound tight but had to move.
But i still think and feel the ICF in the long run is better Fire resistance, and tornado resistant, termites not a problem,I would like wood heat but were I live and lack of close fire department, my insurance rates double from an already high rate! Would end up costing more in the long run. Better to add some solar or PV panels and get a grant. for the cost of a good wood burning stove and associated chimmeny et all. Some jurisdictions are banning wood stoves.Have you thought of a post and beam infilled with straw bales?
Just rambling as I can't get to work as I'm Snowed in! My wife has the 4x4!!!
shoe... i have no idea what a Modified SRC wall is .... can you elaborate ?Mike Hussein Smith Rhode Island : Design / Build / Repair / Restore
http://www.cmhc-schl.gc.ca/odpub/pdf/65863.pdf
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
I see your point about little gain for a large
amount of embodied energy.
I'd be interested to see what an increase of the exterior insulation
would do to the Mass performance. Oh, welcome back.
Edited 12/19/2008 6:59 pm ET by Henley
Riversong,
I don't know anything about Larsen Trusses. If your house feels rock solid to you, gives the feeling of security, then hooray for you. Mine does too. I'm not in a position to compare.
I can compare it to ordinary wood frame houses. I've lived in a number of them and built a few too. This house feels different. I have built houses in the R2000 style, which usually means 2 x 6 framing, sheet metal wind braces, 1 1/2" of foam outside, fiberglass in the studs. I have sometimes felt that if the whole roofing crew swayed together, they could bring the house down.
Flimsy, weak, fragile, vulnerable. There is no satisfaction to be found in slapping together jimcrack boxes like that.
My point is that my house gives me, oddly enough, the impression it was cast in place, especially in very bad weather. There isn't a quiver, a shake or even a vibration that I can detect. It is in this way fundamentally different from even the best built wooden house, which will always have some movement in it. And that makes a world of difference to the way you think about your home.
On another matter, the CMHC study did not conclude, to quote you, "Side-by side house analyses performed by NAHB Research Center and CMHC (Canada) has demonstrated that an ICF house is no more tight or energy efficient than a wood-frame house." That's your conclusion.
The rest of your assertion is undeniable. In a pure heating situation, the foam is all there is. Which contradicts your statement in what, the second or third post in this thread that there is a higher "effective R value" due to the mass?
I don't see that as a serious contradiction, though. I think the mass of the walls and the rate at which they give up heat help to extend the no-heating season at both ends compared to wooden houses.
Anyway, heat is not much of an issue. My phone adn internet bill costs twice what home heat costs. I wish I could nail something together that would cut that down.
Ron
"Flimsy, weak, fragile, vulnerable. There is no satisfaction to be found in slapping together jimcrack boxes like that."
That's entirely a function of quality of materials, design and construction. There are wood-framed houses in Europe that are many hundreds of years old, and colonial American wooden buildings that are more than 300 years old. The Temple of the Flourishing Law in Japan is a wooden building that is 1400 years old.
I am certain that no ICF buildings, nor plastic foam buildings will last anything close to that. Concrete is strong only in compression and requires steel or other fibrous reinforcement to have any tensile or shear strength. Like anything rigid, it is vulnerable to cracking from settling, frost heaving, or seismic activity, and steel reinforcement is vulnerable to corrosion. All plastics have limited half-life and are vulnerable to fire, mechanical and UV damage and insect infestation. All plastics lose their plasticizers over time and become more brittle or more friable.
How many old wooden buildings have you seen which are still standing on their cracked and leaking or spalling concrete foundations?
"My point is that my house gives me, oddly enough, the impression it was cast in place, especially in very bad weather. There isn't a quiver, a shake or even a vibration that I can detect. It is in this way fundamentally different from even the best built wooden house, which will always have some movement in it."
Notice that stiff trees get broken in a storm, while flexble trees bend and remain standing. What gives wood its great resilience is its ability to flex.
"On another matter, the CMHC study did not conclude, to quote you, "Side-by side house analyses performed by NAHB Research Center and CMHC (Canada) has demonstrated that an ICF house is no more tight or energy efficient than a wood-frame house." That's your conclusion. "
I didn't say that, did I? I said "Side-by side house analyses performed by NAHB Research Center and CMHC..." I couldn't include the link to the NAHB study last night because their website seemed to be down. And you obviously didn't search for it.
http://www.pathnet.org/sp.asp?id=1005
<!----><!---->Insulating Concrete Forms: Comparative Thermal Performance <!---->
Prepared for:<!----><!---->
U.S. Department of Housing and Urban Development<!----><!---->
Office of Policy Development and Research<!----><!---->
<!----> <!---->
Prepared by:<!----><!---->
NAHB Research Center, Inc.<!----><!---->
Upper Marlboro, MD
August 1999
<!----> <!---->
Comparative Thermal Performance contains results on energy and thermal comfort performance, as well as computer modeling of energy use. Three homes were built and monitored. One home has an ICF plank system, one has an ICF block system, and one is of conventional 2X4 lumber construction. The homes have identical floor plans. They are located side-by-side on the same street in Chestertown, Maryland. <!----><!---->
All three homes, which were unoccupied, were set up for long-term energy monitoring. Two of the homes were also monitored for thermal comfort analysis per ASHRAE Standard 55-1992. Weather data from the site were used in the energy use computer modeling program, Building Loads Analysis and System Thermodynamics (BLAST), to compare predicted energy performance of the homes to actual energy use. <!----><!---->
Key findings include the following: <!----><!---->
There was not significant difference in air leakage test results among the three homes. This lack of difference may reflect the dimensions, volume, and relatively limited wall area of these simple, affordable homes. <!----><!---->
The two ICF homes were approximately 20%more energy efficient than the wood-frame house. This difference is largely due to the higher effective R-value of the ICF walls and continuous insulation at the slab. <!----><!---->
BLAST modeling of energy use produced results very similar to actual energy use. The results suggest that the contribution of thermal mass and ground-coupling effects to the overall energy efficiency of the ICF homes was not significant. <!----><!---->
While no dramatic thermal comfort differences were apparent between the ICF and the wood-frame homes, several thermal comfort measures showed slight but significant better performance for the ICF homes. <!----><!---->
"In a pure heating situation, the foam is all there is. Which contradicts your statement in what, the second or third post in this thread that there is a higher "effective R value" due to the mass?"
Not really. In a steady-state heat loss analysis (which is how R-value is determined), only the thermal resistance of the materials matters. But in a dynamic environment, with daily temperature swings, a mass wall - if it is thermally coupled to the conditioned space - will dampen the indoor temperature variations because as heat is lost into it much of it is absorbed before passing through. Masonry requires approximately 1 hour per inch to store or dissipate heat, so it slows the changes in heat flow direction. While this does not increase the conductive efficiency of a wall, it can increase the human comfort level by maintaining more uniform temperatures.
"I think the mass of the walls and the rate at which they give up heat help to extend the no-heating season at both ends compared to wooden houses."
Not at both ends. A high-mass building takes longer to either heat up or cool down, so at each end of the heating season it's less efficient, and it's less efficient if indoor temperatures are allowed to vary (set-back thermostats are not very effective in high-mass homes or high-mass heating systems for this reason).
Also thermal mass has less effect if it's sandwiched inside insulation and even less if it's outside the insulation. It is for this reason that I always insulate a foundation on the outside.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Edited 12/20/2008 7:47 am ET by Riversong
Edited 12/20/2008 7:48 am ET by Riversong
Edited 12/20/2008 7:51 am ET by Riversong
Edited 12/20/2008 7:58 am ET by Riversong
You just wanted to say "friable".
You just wanted to say "friable".
Like an egg. Over easy?
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Riversong,
You can't seriously think of comparing medieval wooden buildings to the style of stick framing I was referring to, can you?
This is an argument by misdirection.
By the way, R2000 refers to a standard of airtightness and insulation, not to a particular style of construction. The construction I outlined, and a thousand additional details, make up what is commonly called "R2000 style" by the people I know.
I am not a certified R2000 builder.
Ron
You can't seriously think of comparing medieval wooden buildings to the style of stick framing I was referring to, can you?
You seemed to be suggesting that it was in the nature of wood-frame buildings to be "flimsy, weak, fragile and vulnerable". I was merely indicating that there is nothing in the nature of a wooden building which makes it any of those. There are simple Appalachian shacks which have been standing intact for a couple hundred years.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
There are simple Appalachian shacks which have been standing intact for a couple hundred years.
Mine has been around for about forty, though it was only meant to stand for five or less. It's about two miles from the Appalachian Trail, in New York State.
BTW, welcome back. And thanks for introducing some good reference materials to this discussion, along with your experience and personal point of view.
The house I'm planning to build in NY State later this year will be three stories. Code prohibits more than two top stories being wood framed. My current plan is to form and pour concrete walls, all above grade, for the bottom floor which will serve like a walk-out basement, opening to the lower level lawn and gardens.
I'd like to insulate the outside of those walls, so as to gain the advantage of their thermal mass. Have you ever done something like that or is there a web site you can point out? I'm mainly interested in hearing about and seeing successful methods.
HVC
The ICF product you were considering, Quadlock, sells little polypropylene clips that can be mechanically fastened to a surface for retaining their EPS panels.
It might be possible to devise a way to fasten those clips to concrete with a Hilti or Ramset gun without too much breakage. A Hilti rep could certainly advise you on that.
That would give you a solidly fastened 2 1/4" or 4 1/4" thick EPS panel outside the concrete, where it will do the most good.
Another option is to use a synthetic stucco base coat as an adhesive to fasten XPS to the concrete. I have done this on the inside in a reno. I don't really know how it might hold up in the long term outside.
Ron
Ron,
Those both sound like good methods to me. What would you use as an exterior finish on the EPS?
HVC,
If you use the quadlock system, your options are wide open as they have fastening strips like any ICF. Siding or synth stucco above grade, parging at grade and waterproofing membrane or dimple board below.
Here's the product: http://www.quadlock.com/retrofit_insulation/
Would you cantilever the upper walls to align the surfaces of the wood walls and the foam?
I never looked at Quadlock before I saw your link here. It looks like an interesting product. One drawback I see in the ICF applaction is that their ties are 12" apart and the thinner foam option is only 2 1/4" thick. I would foresee the foam bulging between webs. I have seen foam bulging between webs in Integra Spec, which has 8" centers and 2 1/2" foam. The closer webs and slightly thicker foam would make Integra Spec nearly twice as stiff between webs as Quadlock.
I'd like to see a Quadlock job being poured.
Ron
Would you cantilever the upper walls to align the surfaces of the wood walls and the foam?
I've had in mind to build a short roof onto the bottom of the woodframed wall above, as protection and visual break for the 4+" of EPS insulation as well as shade for the east and south facing glass.
The major feature of this building site is a grand view in those directions so there will be a lot of glass which needs to be at least partially covered to control heat gain in the summer.
The concept is to repeat the main roof line over each floor, beginning just below the windows above.
I never looked at Quadlock before I saw your link here. It looks like an interesting product. One drawback I see in the ICF applaction is that their ties are 12" apart and the thinner foam option is only 2 1/4" thick. I would foresee the foam bulging between webs. I have seen foam bulging between webs in Integra Spec, which has 8" centers and 2 1/2" foam. The closer webs and slightly thicker foam would make Integra Spec nearly twice as stiff between webs as Quadlock.
As Quadlock has its origins in Europe where it's system has been in use for some time, I expect that they have ironed out any of those problems.
Edit: I just remembered that the Quadlock foam is more dense than any of the others I saw at that show. I don't know whether that makes it better structurally, for pouring concrete, but I'm sure it adds to the R-value.
I'd like to see a Quadlock job being poured.
I spoke to their SoCal dealer/contractor about visiting his next job when I met him at the Pasadena show where I first saw the product. He seemed open to the idea but neither of us followed up later. I saw so many ICF systems that day, I'm surprised that I remember any of the people I spoke with.
Quadlock has a free, professionally produced DVD showing the installation of their ICFs. I have a copy which I picked up at the show booth from the dealer. Shouldn't be difficult to get one from their distributor.
Edited 12/20/2008 6:51 pm by Hudson Valley Carpenter
Peter... in regards to mass inside or outside the envelope.......
couple things i've thought about over the years...
as you know ... we were very involved in active and some passive solar space heating from '75 to about '86
in our active systems we developed whole house water collector (drain back ) systems with massive concrete water storage tanks
then we linked that system with water-to-air heat pumps
then we dropped those and went to hot air collectors with rock storage in concrete tanks
and hot air collectors with radiant slabs using Air Crete forms developed before WWII in California
while we were doing this... in a parallel universe, others were doing their own thing.... like the double -envelope house (passive )
and there were a lot of passive houses built with trombe walls
most of the trombe walls used direct gain thru south glass and quarry tile floors
our observations boiled down to a lot of things...
but we found that the trombe wall was superfluous.... most of the heat gained could be stored in the quarry tile floor
and... most of the heat we gained from our hot air collectors could be stored in the mass of the house.... the rock storage was an exra expense.... the trombe wall was an extra expense
after about '86 i also became convinced of a few more things
1) we mostly have a severe heating requirement for 3 months....December...January... February---------go furthur north and you can tack on November and March to that... so 5 months
2) the other 7 - 9 months... are progressively :
little heat/ closed windows..... open windows/ screen doors ....
closed windows w/ a/c..... open windows/screen doors....
little heat/closed windows... so the heating season requires super insulation.... which costs an order of magnitude LESS than active solar
and good windows to take advantage of passive solar gains
the a/c season requires super insulation and strategic overhangs to reduce solar gain
but one thing NONE of these require is additional mass ... we have all the mass we need in our gypsum wall board, flooring, and fourniture..
if you insulate the exterior of your foundation you will incurr an extra expense, and you will still have to stud the interior if you intend to finish that space
i like full basements.... if the budget allows ... but when we do that, we put treated eps foam from the footing to the bottom of the subfloor... so, we isolate our slab ( 2" ).... and we stud the wall and blow it with dens-pak cells (say a total of R19 )
lets assume the underlying soil temp is 45 deg........ that is a considerable heat loss just thru the footing alone... if you develop a cone of heat influence under the footing... perhaps the soil will rise in temp... some say it does... but i think that cone can only be maintained by a steady state loss from the conditioned space
so... the way we do our full foundations is as i described above AND we put 2" uder the full slab too
i assume you want 3 stories because of a view... if this is mountainous terrain and the first story is say...... a 9 ft. foundation, won't that normally be a walk-out ?
if you go icf's for the found... that would be good.... i guess... would the walk-out portion be framed ? or is that a code problem too ?
one problem i have with icf's ( in my head ) is attaching trim and siding.... the mfr's solutions always look self-defeating to me
what code are you designing under that won't allow 3-story wood frame ?
Mike Hussein Smith Rhode Island : Design / Build / Repair / Restore
Edited 12/20/2008 7:34 pm ET by MikeSmith
Mike,
That's an excellent synopsis of your long experimental efforts and your conclusions. Thanks for that very helpful perspective.
I didn't know that you'd been so interested and active in solar homes.
I've only tried a couple of passive solar ideas, over the years, neither of them based on anything but my own experience with poorly designed homes where I'd lived and my sense of what should work. Consequently they only worked well when conditions allowed them too.
Winters in the Mid-Hudson Valley are pretty dreary, only about one day of sunshine to two days of obsured conditions. Therefor it's not worth the expense to add solar heat to the equation. I learned that fact very well over many winters in my little cabin with the big glass passive living room. Great view, even when it was just the surrounding forest, but hard to heat.
I'll try to work out the glass, the floor composition and overhanging roofs so that the winter sun will have some where to land and add some gain.
I'll certainly reconsider the exterior EPS insulation on concrete walls. That didn't really appeal to me but it seemed like a good way to moderate temperatures inside. And of course, being a typical old time carpenter, I didn't want to waste an opportunity to save some money on heating costs.
The two story wood framed limit is according to my architect in NY State. I don't know where he got that but he's mentioned it a couple times in the past. He's worked in NY State for many years so I assume that he knows what's up.
The 4 acre lot, ~300'wideX600'deep, is on the low side of the road which runs pretty level, parallel with the ridge line. The drop in elevation from the road to the far side of the house, the east/south/east (big view) side is about twenty feet. So I'm planning a short, level driveway, perpendicular to the road, directly into the garage with the house attached behind.
The main living area is on the top floor, the bedrooms below and the recreation/shop area on the bottom level. All three levels will have a nice view but the top level will be panoramic, nearly 180 degrees with a fifty+ mile vista, across the Hudson Valley.
If you think of anything else that fits this proposal, I'd appreciate your advice.
Peter
east bank...or west bank ?
above bear mountain ?
above poughkipsee ?
it's a long riverMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
West of the Hudson river, on the east side of the northern Appalachians, called the Shawanga or Shawangunk ridge. It's the first ridge east of the Delaware river valley, about thirty-five miles from the Hudson river. The elevation is ~1200 ft above sea level.
The Mid-Hudson, as that part of the valley is known locally, is about fifty-sixty miles wide from Kingston down past Newburgh to Cornwall, which is a few miles north of West Point.
Bear Mountain is a few miles south of West Point.
BTW Mike, what do you think of this product? http://www.superiorwalls.com/products_r5.php
Edited 12/21/2008 3:38 am by Hudson Valley Carpenter
Mike,
I knew that you had been seriously into solar but I am still surprised at the breadth or your experience.
You said, "if you insulate the exterior of your foundation you will incurr an extra expense, and you will still have to stud the interior if you intend to finish that space"
There's one of the reasons I first got into ICF work about 13 years ago. ICF almost always costs less that pouring a conventional wall then framing and insulating the inside. If you insulate outside of the conventional wall, too, it's no contest. Saves a little space, too.
Ron
NONE of these require is additional mass ... we have all the mass we need in our gypsum wall board, flooring, and fourniture..
That's true only if the solar glazing is kept below 7% of floor area. Every square foot of south glazing beyond 7% requires:
5.5 SF sunlit thermal mass floor<!----><!----><!---->
8.3 SF thermal mass wall<!----><!---->
40 SF thermal mass floor not in sun
<!---->Beyond 12% of floor area generally requires an active system with remote storage and mechanical distribution.<!---->
<!----><!---->
<!---->This was the mistake commonly made when passive solar caught on in the 70s. Either far too much glazing with insufficient mass and no overhangs or too much mass and complicated active systems (even the envelope house is highly questionable in its passive functioning).<!---->
<!----><!---->
<!---->You are right, however, that trombe walls and remote storage (and even attached sunspaces) are less efficient (and more costly) than simple south glazing:<!---->
<!----><!----> <!---->
SOLAR COLLECTOR EFFICIENCY<!----><!---->
•double-glazed windows 50%<!----><!---->
•dgw with R-4 shade 60%<!----><!---->
•thermo-siphon air panel (TAP) 34%<!----><!---->
•TAP with fan 40%<!----><!---->
•greenhouse/sunspace 20%<!----><!---->
•sunspace with fan 35%<!----><!---->
•flat-plate collector with fan 40%<!----><!---->
<!---->
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
5.5 SF sunlit thermal mass floor<!----><!----><!---->
8.3 SF thermal mass wall<!----><!---->
40 SF thermal mass floor not in sun
SOLAR COLLECTOR EFFICIENCY<!----><!---->
•double-glazed windows 50%<!----><!---->
•dgw with R-4 shade 60%<!----><!---->
•thermo-siphon air panel (TAP) 34%<!----><!---->
•TAP with fan 40%<!----><!---->
•greenhouse/sunspace 20%<!----><!---->
•sunspace with fan 35%<!----><!---->
•flat-plate collector with fan 40%<!----><!---->
Thanks for supplying those figures but I'm not knowledgeable enough to make any sense of them. Maybe you can explain how they apply to the home I'm proposing.
I'm not certain of the % of total glazing vs floor area for the three story home I've described but I'm sure that the top floor will be over 12%, probably about 15%. The bedroom level will be around 10%, with the lower level at about 8%.
I plan to shade at least 80% of the glazing from the summer sun. I also expect to add some kind of insulated panels, similar to bi-fold doors, as interior night time winter window covers.
The winter weather conditions in the area aren't condusive to solar heat gain, only about one day of sun for every two days of clouds.
Any thoughts?
Edited 12/21/2008 2:45 pm by Hudson Valley Carpenter
My current plan is to form and pour concrete walls, all above grade, for the bottom floor which will serve like a walk-out basement, opening to the lower level lawn and gardens.
I'd like to insulate the outside of those walls, so as to gain the advantage of their thermal mass. Have you ever done something like that or is there a web site you can point out? I'm mainly interested in hearing about and seeing successful methods.
I've never poured an above-grade "foundation", but if code limits you to something other than woodframe for base floor, you might check out Superior Walls. They're 5,000psi precast reinforced concrete-stud/plate walls with R-5 rigid foam board cast in to the outside. additional insulation can be added between the "studs", which are pre-punched for wiring. They require only a level crushed stone pad underneath, and are bolted together and caulked with a HD urethane sealant. They can be designed for any configuration and with door and window rough openings preframed to any size.
http://www.superiorwalls.com/products_r5.php
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
RS,
That's another interesting product and method you've contributed. Thanks.
I'll have a good look at the web site and see how it might suit my plans.
OK, I've had a better look at the R5 system.
Do you know what method they advise for insulating a poured concrete floor, inside those walls?
Do you suppose that it would be possible to pour an insulated slab on a gravel bed first, then set the R5 walls on top of it? I'm considering ways to insulate/isolate the bottom of the R5 wall, to avoid heat loss into the gravel bed.
HVC
There's a bit of a discussion going on at GreenBuidlingTalk on Superior Walls which involves some people who are experienced with it.
https://gbt.buildcentral.com/Forums/tabid/53/forumid/4/postid/46975/view/topic/Default.aspx
Ron
that's an interesting site.... some of those posting know very little about foiundations other than teir personal bias for icf
here's my bottom line... all of these schemes are so superior to conventional construction... pick one and explore the options... but doble check all the claims
hey....what ever happened to that discussion about the miracle electric heat glazing ?Mike Hussein Smith Rhode Island : Design / Build / Repair / Restore
Ron,
Thanks for the link to that discussion. Interesting reading. Reminded me that my goals wouldn't all be compatible with the Superior wall. Nonetheless, the R5 wall looks like a good system for some situations.
Do you know what method they advise for insulating a poured concrete floor, inside those walls?
Do you suppose that it would be possible to pour an insulated slab on a gravel bed first, then set the R5 walls on top of it? I'm considering ways to insulate/isolate the bottom of the R5 wall, to avoid heat loss into the gravel bed.
I've seen only one of these go up here in VT (an Energy Star nightmare, because of the thermal bridging in its all-steel floor framing). As far as I know, they make no recommendations about anything other than the wall system. This house had a radiant concrete slab poured over poly and XPS inside the wall system. I don't recall if it had slab edge insulation (since the walls are insulated outside, this may not be necessary).
My understanding is they want a gravel bed to set the walls on. There shouldn't be much heat loss to a dry crushed stone (3/4") bed.
As you can see from the pictures below, they will pre-install PT door and window frames, fabricate the walls for any crazy angle, and the concrete "studs" have thermal breaks built in and electrical conduits.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
There shouldn't be much heat loss to a dry crushed stone (3/4") bed.
The only major difference is that my "basement" is going to be above ground, on all four sides. Assuming perfect drainage, how many inches or feet of stone do you think would be required to mitigate the effects of frost on dry crushed stone? I mean, isn't there a pretty strong thermal bridge going on in such a stone bed?
On the other hand, maybe I'm fixating on one small area of bridging which can be made less significant by eliminating most of that effect. Using the Mooney idea on the interior of the R5 wall would take care of most of that concern I would think.
Just mumbling to myself here. Don't give it too much thought. You may end up in the same quandary. ;-)
Edited 12/21/2008 11:14 am by Hudson Valley Carpenter
Assuming perfect drainage, how many inches or feet of stone do you think would be required to mitigate the effects of frost on dry crushed stone? I mean, isn't there a pretty strong thermal bridge going on in such a stone bed?
There are no frost effects on well-drained granular fill, let alone crushed stone. Frost-active soils have at least 5% silt content, have high water storage capacity and high capillarity, and a source of ground moisture.
Course crushed stone, if dry, will have very low thermal conductivity (it's mostly air and has very little surface contact area.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Riversong,
I believe you are deliberately misunderstanding what I have been writing in order to get a fight going.
Ron
now ron..... can we spell paranoia ?
'member the story of the scorpion and the frog ?Mike Hussein Smith Rhode Island : Design / Build / Repair / Restore
I believe you are deliberately misunderstanding what I have been writing in order to get a fight going.
That I would never do. I'm merely responding to what you've posted. If you feel I'm misrepresenting what you've said, then it's your responsibility to clarify - rather than make unfounded accusations.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Riversong,
I do not mean to offend you with unfounded accusations.
I am just going to drop it, though. I really don't want to go through an "I said and then you said" thing. Too dreary.
My writing is not that opaque, though. And you are not that dim.
Oh, I did read that NAHB study. I had never seen that one before. I was interested to see that the second highlight they noted was that the ICF houses used 20% less energy on heating than the other house.
Ron
Oh, I did read that NAHB study. I had never seen that one before. I was interested to see that the second highlight they noted was that the ICF houses used 20% less energy on heating than the other house.
Read it again. What they said was that the 20% improvement in efficiency was entirely related to the 20% additional R-value over the 2x4 house and the ICFs were neither more airtight nor more energy efficient per R.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Riversong,
I saw that. I don't expect anything else.
The point is that those ICF houses built in the normal fashion use 20% less heat energy than a wood frame house built in the most common fashion.
We know it is possible to build a wood house which will use less or the same energy as a typical ICF house. It just isn't done very often. And they still move.
Ron
"The point is that those ICF houses built in the normal fashion use 20% less heat energy than a wood frame house built in the most common fashion."
Normal? 2x4 R-11 houses are a thing of the past. The bare minimum to meet today's energy codes is 2x6 R-19.
If you can make your point only by comparing apples to oranges, then you don't have a point.
The conclusion of that study was that ICFs offer no more energy savings than an identical wood frame wall with the same R-value.
Why are you unwilling to acknowledge that?
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Riversong,
I am not arguing that a wood frame wall and an ICF or another wall with the same R -value will lose different amounts of heat. I thought I said that quite clearly.
Here's what your NAHB study said:
The two ICF homes were approximately 20%more energy efficient than the wood-frame house. This difference is largely due to the higher effective R-value of the ICF walls and continuous insulation at the slab.
I understand that the difference is because the houses are different and insulated to different standards. That (apples and oranges) is a fair representation of reality.
What is the R - value of a normal 2 x 6, 16" oc wood framed wall with fiberglass insulation and OSB sheathing? R 17? R 18? And that can be reduced to very little by poor workmanship in the insulation installation or the least little draft. Any ICF wall gives you R 17 or R 18 and will be airtight without having to put any special effort into the construction and without having to rely on the craftsmanship of an insulator.
I believe that there are very few standard built wood frame house which ever reach their potential insulating value. On the other hand, it's hard to build an ICF structure that doesn't reach its full potential.
Ron
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You continue to compare an ICF house with a poorly-built or sub-code wood-frame house.
What the study said was that there is no energy advantage to an ICF house over a wood-frame house.
Any wood-frame house built to today's minimum energy code standards will perform as well as an ICF house. With a small additional effort, a wood-frame house can easily outperform an ICF house.
The more salient issue is the environmental impacts of the materials. ICF (concrete and petrochemical foam) has extremely high embodied energy, very high global warming contribution, and a variety of other toxicity issues at both ends of the life-cycle.
From an ecological and sustainability perspective, it's very hard to justify an ICF home.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Edited 12/21/2008 6:46 pm ET by Riversong
Rivresong,
The environmental impact of ICF vs. wood frame is a very interesting question. I think it's worth starting another thread in the Green Building folder.
Shall we meet there?
Ron
By the way, a study performed by the US Oak Ridge National Laboratory on comparative thermal advantage of different configurations of mass and insulation demonstrated that the most mass benefit occured with exterior insulation, second best with concrete-insulation-concrete (CIC), third with ICI (like ICFs), and least with interior insulation.
In all ten cities evaluated, exterior insulation on a mass wall significantly outperformed ICFs, with the most difference in warm climates.
http://www.ornl.gov/sci/roofs+walls/research/detailed_papers/thermal/index.html
http://www.ornl.gov/sci/roofs+walls/research/detailed_papers/thermal/figures/figure5.pdf
http://www.ornl.gov/sci/roofs+walls/research/detailed_papers/thermal/figures/figure6.pdf
http://www.ornl.gov/sci/roofs+walls/research/detailed_papers/thermal/figures/figure7.pdf
http://www.ornl.gov/sci/roofs+walls/research/detailed_papers/thermal/figures/figure8.pdf
The mass advantage was greatest between R-13 and R-17. Above that range, the advantage diminished, and below that range there was a disadvantage.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Edited 12/20/2008 8:45 am ET by Riversong