What are my insulation options?
I’m building a new workshop. The size is 30′ x 50′, 10′ walls, vaulted ceiling. The attachment is a pic of a typical truss. Heat will be low intensity infrared tube. I live in Montana and we get chilly weather from time to time.
I’m already convinced sprayed foam is the way to go for the roof but I’ve still got a few questions…Can I have the foam shot on to the underside of the roof sheathing and skip venting? would 4″ be enough? Would the addittion of fiberglass batts be worth it? Would the air aspace between the foam and the drywall be a problem?
Walls will be 1″ foam and fibergalss batts.
I’m looking for any help you guys can give me. I usually do the pinky-pointing furniture thing but I’ve spent quite a bit of time with a big hammer in my hand, too.
Thanks,
Lee
Replies
Hi, as for your question of whether or not 4" of insulation is enough..I believe that would only give you about an r-20 (depending on the product..icynene (sp) ?) That seems abit light.
As for ventillation...what kind of roofing are you installing ? Typically (in my area anyway) if you're useing metal roofing you'd be ok. If your're not useing metal, you may wish to read whatever the mfr. requires.
I am assuming you are installing gyp. to the interior ? If so, just remember to install a good vapor-berrier and you will be ok.
Are you installing a vapor berrier to the underside of the slab ?
Are you installing any rigid insulation under the slab ? (or down to the footing) ?
I envy you building such a structure !!! Sounds like it's going to be great !!
Hey Tigger,
I can go thicker with the foam to get the Rs up there...could I supplement with fibergals? If so where...between the bottom chords or against the foam? Since the insulation is so far from the drywall should I try to recover the heat that gets up into that cavity?
Roofing will be asphalt shingles...T-locks
No vapor barrier under the slab...it's a desert here and moisture from that source is actually welcome, heck, I've even wet the floor with snow and buckets of water trying to get the humidity higher at certain times of the year.
No insulation under the slab either, the slab is monolithic, about 12" around the perimeter.
Lee
http://www.furniturecarver.com
I think you should have the ceiling blown with loose fill insulation. More R-value/$. That way, you will have ventilation between the insulation and the roof surface, thereby having less chance of ice build up on the roof.
Matt
Edited 12/21/2003 2:00:17 PM ET by DIRISHINME
Lee, The blown cells will probably be cheaper if you are using a finished skin on the interior.
but I suggest that you give the local Corbond people a chance to show youwhy they believe that total spray faom on the whole package is the better way to go. When you seal the whole thing from top to bottom against infiltration this way, you don't need venting or as much R-value. gerneral rule is 2" walls and 3" ceiling/roof.
They are glad to sell you more thickness, but they hace charting to demonstrate from historical evidence and studies, that you would likely be wasting your money.
I would definitely avoid fibreglass batts anywhere that it is so cold and windy as your state.
Excellence is its own reward!
Thanks Piffin,
I'll give them a call. Is there any real difference between the various spray foams? Is one any better in real terms than another?
Also, I'll be using a wood stove in addition to the infrared heat so there will be heat stratification...I'm still a bit concerned about the cavity between the inside face of the foam and the drywall in the roof. Since there's not likely to be fiberglass there should I try to recover that heat with some sort of ventilation fan or should I just write it off, perhaps I'm looking too hard for problems that just don't exist.
Leehttp://www.furniturecarver.com
Re your question - what's the difference - the spray foam that Piffin referred to (Corbond) is a polyurethane foam I believe. There are several manufacturers of polyurethane foams. The basic difference is the density of the product - PCF - pounds per cubic foot, of the different products. Generally, the more PCF, the higher the R-value per inch, but also the price goes up somewhat proportionally. If you are not too space constrained (like 2x4 walls) , the R-value per inch is less important. Also there are various additives such as flame retardants and mold inhibitors. One thing I don't know is if any of the site installed spray foams have a insect inhibitor such as boric acid (or a derivative).BTW - I looked at your web site. Fabulous art work...
Let us know what you find out in terms of $$ and what your final decision is. I'd be quite interested.Matt
Lee, closed cell polyurethane can yield R-7 per inch, and will add some stiffening to stud structures.
The open cell foams are about R-3.5 to the inch, and are more spongy.
In my opinion, the #1 advantage to foams is the sealing effect you get in every crack that is covered, the# 2 is the good R-value for limited space. If you have the space, then I would go with a combination of closed cell foam for the air seal, and follow with cellulose or fiberglass for the remaining R- value desired. PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
Lee,
The urethene foams are vapour barriers as well. If properly applied, they yeild up to 7.2 R-value.
The icynene isoanurate(?sp) foams are not vapour barriers and only yield about R5 as I understand it.
I have used another uretheyne foam but have migrated to the Corbond in large part because it contains borates to prevent insect hospitality issues. borate happens to be a mold preventive also, but I'm not sure why that would be necessary since the product itself eliminates dew points and is a Vapour bar. It provides no food for the mold or bacteria.
Another reason I migrated to Corbond is that it off-gasses far less than the other urethene I had used previously. next morning there was no noticeable odor with Corbond. The other tened to leave odors for up to a week, depending on air temps.
I believe they have all mostly eliminated the toxic gasses now tho. It would be a Q worth posing to those you interview for the job.
Let that air chamber above the sheet rock stabilize. Sucking the air through constantly to recycle the BTUs is just likely to suck excess moisture into that cavity where it could remain behind. But that is only me surmising. I just don't think there is anything to gain from the excercise in recapturing that small amt of heat energy.
I believe that your area is a home stomping grounds for the Corbond outfit..
Excellence is its own reward!
Piffin -
I think that 7.2 R rating is currently somewhat controversial. The high initial R value is said to be the result of the trapped blowing agent which eventually bleeds off. Some claim the final value will level off around 5 something, about the same as the Urethanes without the special blowing agents such as Icynene, which is generally listed as a modified polyurethane.
There has been quite a bit of discussion of the qualities of Icynene on some discussion boards. The company and those who install it claim that Icynene seals all leaks and does not need a vapor barrier. Yet, the same advertising claims that Icynene is open cell and will allow water to drain out. Not quite sure just how that works.
The idea there is that when you insulate well enough to eliminate convection currents and dew points, there will be no condensation.
You can theoretically approach the same effect with denspack cellulose..
Excellence is its own reward!
Thanks to all of you for the input. These messages added to the great info that came via e-mail have made me less of a dummy about spray foams. I'm going to talk to a couple of foam contractors and probably go with straight foam in the roof and, depending on the price, foam and FG in the walls, closed cell throughout.
Leehttp://www.furniturecarver.com
lee... i don't know if you've ordered your truss yet... we use a lot of scissor trusses.. BUT we order our with a typical 12" ENERGY HEEL... then we blow 24" of cells into the space..
at your pitch you would be blowing full depth by the time you come in about 3'..
you wind up with an installed R-value of about 60 .... and about 40 on the perimeter...Mike Smith Rhode Island : Design / Build / Repair / Restore
lee... here's an energy heel..
and a pic blowing the cells AFTER the ceiling is installed..Mike Smith Rhode Island : Design / Build / Repair / Restore
Mike,
the old part of my house had exactly that sort of insulation. the walls were all fiberglass and the roof was blown in cellulose.
Heating bills in excess of $300 for two or three of the heating months here in Minnesota. that's with a brand new high efficency gas furnace tuned up every fall.. Anderson windows with Low E etc..
It was built very carefully with with the correct vapor barrier and every thing properly inspected.. By mid winter the insulation in the ceiling wasn't doing anything.. it was a sodden mass of frozen ... guck!
Heat would work it's way past the insulation ( in part because of the thermal bridge of each rafter) hit the cold roof which then frosted over.. first warm day and it would melt causing it to get the cellulose wet and further reducing it's effectiveness..
I actually had better luck when I forgot to put the attic access back in place and the heat that came out kept the insulation dry most of the winter! I plugged the vents and stuffed rags into the ridge cap and it was both warmer and cheaper.. effectively I had no insulation (except whatever insulation the plywood and shingles offered..)
snow melted quickly on my roof.. but The year I did that my heating bill wasn't any worse in spite of a colder winter..
Try this,
take a bottle wrapped in cellulose and pour boiling hot water into it.. let go before you burn your hand..
now take the same bottle, spray a layer of foam on it and grab it, now pour that same boiling hot water into it.
what can i say , frenchy..... if you're not controlling your internal moisture.. you're screwed anyway..
we don't have wet cellulose... and heat doesn't work it's way past the insulation due to thermal bridging...you had major air leaks ... you had a mini-climate.. it was fuggin rainin in your attic..
don't blame that on cellulose... sheeeesh .. louise....Mike Smith Rhode Island : Design / Build / Repair / Restore
<<<<< Try this,
take a bottle wrapped in cellulose and pour boiling hot water into it.. let go before you burn your hand..
now take the same bottle, spray a layer of foam on it and grab it, now pour that same boiling hot water into it. >>>
lessee if i got the scientific procedure down ?
wrap a bottle in cellulose... let's say two inches.. R7
pour boiling water into it.... ok..
now do the same with R7 of foam.. pour boiling water into it..
ok..
WHAT'S THE DIFFERENCE ?
let's do the other one.. i've done this one..
grab a handful of cellulose... place a penny on top of it.. light a torch and melt the penny...
now grab a handful of foam.. put a penny on it.. now grab a torch and melt the penny ... wait stop... don't do that !
yeah , so what ?
if you want foam ... go ahead , use foam, it's great, it's expensive, you need a specialty sub to install it
just don't confuse your problem with a leaky attic with a failure on the part of cellulose.... Mike Smith Rhode Island : Design / Build / Repair / Restore
Not a leaky attic!
Oh and That isn't the only way to get foam. you could also buy SIPs
Frenchy:
You said: "every thing properly inspected.."
If you are referring to inspections by local government building inspectors, many people are under the misconception that building inspectors insure quality work. Actually, all they do is enforce a minimum set of standards called a building code. If the ceiling has 300 leaks in it the size of your little finger around light fixtures, bath fans, etc, generally speaking, they could care less. Their only job is to see that the insulation was installed to a thickness to meet the required R-value. If nary a one of your outlets had insulation put behind it, do you think a building inspector would check for that? Were all electrical, plumbing, etc penetrations fire caulked, or otherwise draft stopped?
Sounds like an overload of interior moisture coupled with air leaks is your problem. For starters do you have bath and kitchen fans of adequate sizes that are vented to the outside of the house, and do you use them? Is your dryer properly vented? Do you have a whole house humidifier that is out of wack? Where is all that moisture coming from?
Lee:
Just as an FYI, that energy heel truss configuration Mike is referring to is also called a raised heel truss. Matt
Well, not only are the trusses ordered...they're here.
The heel cut is 4 3/8". I'm matching a garage roof because the workshop is attached to the garage.
I'm doing the foam, probably FG to supplement The wind howls like a big dog around here. I've used fibergalss and cellulose on our house and another house I've built nearby...I'm ready to use the foam if for no other reason than my own edification. Since the wind howls so here the infiltration barrier will be nice.
Thanks again, guys.
Leehttp://www.furniturecarver.com
I was the inspector of this house prior to purchase.. when I inspected it I took three 12 hour days before I made an offer on it.. Cosmetically it was a mess annd it showed like the city dump (only one light bulb in the whole house worked) I knew I was buying a tear down but a tear down I would have to live in for a while..
The only thing I did like about the house was the care they had used in insulating it.. I was sure that with that care the heating bills would be reasonable.. There was a vapor barrier behind alll the electrical boxes, insulation well above the norm for the area and I never have found anyplace where there were any leaks of any size in the ceiling.
It's simple where all the heat went. The R value of a 2x8 is 2, you put a piece of sheet rock against it and insulation between the bays and every 16 inches you have no insulation.. that heat went up into the attic, condensed on the inside of the roof and the chilled air from the eve vents caused it to condense and poof! frost! first warming spell (like tonight it's above freezing as we speak) and the frost turns back to water and drips off the nail heads etc.. water dripping onto ground up paper isn't a real good insulation..
As further proof of my ideas,
half of the house has SIPs right now, the other half has the insulation I spoke of.
Now the half with the SIPs isn't heated. all of the furnace vents were torn out as I tore down the house section by section.. the only heat in it is what escapes from the half with the regular insulation.. (yes it's pretty open, but no furnace ducts anywhere near that section) It's 63 on the floor of my bedroom in the old part of the house and 64 8 feet higher on the ceiling.. go into the great room (new part of the house, unheated but with SIPs) and it's 66 on the floor but the ceiling 28 feet above is 67
Just for information I'm using a raytek lazer mini temp to get all these temps
But in an unheated portion of the house it's three degrees warmer than the heated portion of the house.. the only differance is those SIPs I spoke of..
it's ok... i still love you...
your ideas about what caused your wet attic are still out to lunch..
the r-value of a 2x8 isn't 2...( unless they're laying flat )... it's 8.. ( nominal )
and heat doesn't carry moisture... air does.. heated air can cary more moisture than chilled air ( that's how dehumidifiers work )...
if it was raining in your attic , which i don't doubt, then your HOUSE was the source of the water... not the exterior.. it was probably your cellar area (crawlspace, slab, whatever )..
or some other GROSS water source ( that would be gross as in large )..
the warm moist air moved thru the house until it hit a condensing surface.. the one you saw was in your attic.. you probably have other condensing surfaces within your walls.. if all you have done is put up sips , then you have denied one condensing surface.. but you haven't said what you did about the water source..
if you haven't stopped the water source, then someplace else within your structure is becomming the contact point between the warm heated air and the dew point..
none of this has anything to do with cellulose insulation , which BTW, is almost universally accepted as a great air diffusion barrier...
we've installed many thousands of board feet of foam products over the years...
in areas where the depth is limited, there is very little substitute for the highR-valu you can acheive with foam..
in an attic ... ( IMNSHO) ....foam is a waste of insulation dollars..
but hey, whadda i no ?Mike Smith Rhode Island : Design / Build / Repair / Restore
There isn't a moisture problem in the house, exactly the opposite. the moisture level in my house is often single digits. (There are three humidistats in the house to check on) When you heat a house in Minnesota winters you dry them out.. Humidity gets so low that skin cracks and dry out, smaller humidifiers often can't keep up and running them full time will still leave the humidity too low.
My wife starts putting lotions and creams on as soon as the heating season starts and still her skin gets dry and flaky
(it isn't always a curse, the dry air allows me to air dry wood to around 7% moisture in about 45 days during the heating season)
The escaping warm air causes whatever moisture there is to condense on cold surfaces.. warm air escapes two ways.. the one you allude to, leaks in the insulation surface and thru convection.. A solid surface like wood will transfer a surprising amount of heat, not as much as metal but far more than Foam..
There are ways to build a house without those thermal bridges that stick building requires. It demands a totally differant mind set to think outside of traditional construction methods.
I think we are talking degrees here..
If, IF! we are talking about traditional stick building then I could be inclined to agree with you. it really doesn't make a lot of differance if you use fiberglass, celluloise, or foam as the insulation medium..The only real differance that I can think of is air movement. Fiberglass will allow the most and foam the least. As for their relative "R" value I can imagine that celluliose if not packed down and kept dry would be better than fiberglas and worse than foam.. It would be easier to blow in celluliose than to properly install fiberglas. Neither celluloise or fiberglas tolerate water very well and retain much insulational value.. while foam is not affect by water..
Fire on the other hand is an issue with foam much more so than fiberglas or celluloise.. Except! with properly installed SIPs then the risk of fire is dramatically reduced.. To pass the test for fire safety they built a bon-fire in the corner of a room made from SIPs and built according to standards. An hour later the fire was out and no damage noted.. Also no off gasing or noxious fumes..
I'm not saying foam is not a better insulator, nor do I think anyone is. It just has a number of caveots. The newer poly type foams have fewer.
Your problem is not rooted in thermal bridging. If your attic is as well insulated as you say, the 2x8 ceiling joists should be covered by at least 4" of insulation. Most houses are insulated as your's is, and they work fine. Yours does not because it has a moisture problem.
Have a good day.Matt
Matt,
read my answer to Mike Smith
Frenchy... c'mon.. most winters we run a humidifier for 3 months.. so , you're no different than us..
if you had water condensing in your attic, it came from your house.. no ifs, ands, or buts...
you said it yourself.. the wisconsin winters are bone dry.. even with snow cover on the ground... because the cold will not carry any moisture.. and the RH gets down to below 10%...so , the outside air was not the source..
so.. you tell me.. if it was raining in your attic ... where did the water vapor come from ?
air leaks move air....air carries water vapor..
AND. if you follow some of the SIPS news, you will see that last year there were a lot of homeowner association suits against builders in Alaska who failed to seal the joints in their SIPS... whole roof assemblies were failing from rot in 4 year old buildings....
air sealing is a problem no matter what kind of insulation you use.. and foam insulators can screw it up as well as the rest of us.. they just have to be more inventive....
Mike Smith Rhode Island : Design / Build / Repair / Restore
Mike,
if the moisture in the house is too low for comfort, even if (and I disagree with your assessment) the moisture is coming from the house it's too low to materially cause the problem I discribed..
Consider this,
Yesterday the moisture outside was pretty high. (too busy to measure it) but it was foggy in the morning (isn't that near 100% moisture?) and during the day it got up to 43 degrees. everything was melting and damp..
Roof vents admit outside air in so during yesterday it was damp as heck in the old part of the attic. right? Overnight it dropped below freezing and the moisture that condensed on the attic from the moisture yesterday would dampen the insulation,... Correct?
remember we have a heat source, heat that transfers by covection thru the joists (even given an R 8 rating, it is still lower than the R30 rating of the insulation..) will warm the area of the attic causing it to be warmer than outside air... with now damp insulation yeilding up further heat the problem will cascade..
Sure on very cold days there is low moisture outside.. but not every winter day is that cold.. and thus not that dry..
As a side issue, thanks for your imput on this subject.. I'm enjoying the conversation regarding insulation.. I arrived at my choice for insulation after a great deal of thought and looking at various issues.. I realize that with stick building there is a matter of speed of assembly.. trading that speed for a differant way of doing things isn't the way to ensure profitablity. As a Pro that is and should be your real priority.. Even when selling equipment there is a point when I let the customer win and use a piece of equipment that is less than optimal for his application.. kinda, "he wants it he can have it," mentality.
You too, must take that approach.. History has taught you that celluliose is OK and that is what you use..
No, I didn't see that article about someone failing to seal joints causing rot.. I can understand it though.. My manufactorer made me install a vapor barrier underneath the Sips. I thought that was kinda dumb (but I did it) now I can see why.. as carefull as I was to seal the joints between the SIPs if there were spots where the joint wasn't perfect, the first line of defence wasn't the SIP itself rather the vapor barrier..
Just to braoden the perspective here a little -
When you mention the fog meaning close to 100% humidity remember that this is a measure of RELATIVE humidity.
100% at thirty degrees is probably not much differn amount of moisture than 30% at 70° because wam air can handle more moisture. Mike has been right in this discussion, not that I'm a great fan of cellulose, but if you have moisture problems in the atic and the roof is not leaking, you need to deal with the moisture in the house by keeping it out of the attic..
Excellence is its own reward!
Piffan,
to repeat myself, the house is/was dry.. too dry.. the only moisture in the house is in the attic.. as an example I can set newspaper on the floor of the basement and it remains bone dry.. I keep flour, household flour in the basement in an open tub. ( I use the flour to remove the black residue from polishing the aluminum on my race cars) it's never cakey or sodden.
the only thing getting into the attic is condensed moisture.. when I first moved into the house there was a near new roof on it without any leaks. I laid in the attic with a flashlite and confirmed it during a driving rainstorm prior to my purchase.. The only way that I can imagine to keep moisture out of the attic, would be to block the vents in the attic..
You are running humidifiers. Where is that moisture going?
The air in the house may seem relatively dry relative to summer humidity levels, but it is wet relative to outdoor levels..
Excellence is its own reward!
depending on a lot of factors, the humidity indoors in the winter is often in the 5 to 8% range.. almost never over 10% unless it's extremely damp outside..
I live on a lake so humidity in the summer is near triple didgets often.
How damp does the celluloise need to be before it starts to lose it's insulation value? the wetter it is the worse the problem can become.. Again, a warm couple of days when everything is melting.. the air will get pretty damp during the day.. that moisture laden air will go any where including in the attic. (right?) now the roof may be still cold from the snow burden on it . the moisture laden air hits the underside of the cold roof and poof,... frost..
the escaping heat will cause the frost to melt and drip onto the insulation.. damp insulation loses it's insulation value and more heat can escape.. Since the attic will never really get warm enough to dry out the insulation (remember the eves allow cold air in and allow the warmed air to exit thru the roof vents..) the insulation stays damp untill the next wet days and the problem worsens.. eventuallty by January I could look up in the attic and touch the insulation and feeel a frozen block that doesn't dry out untill the first really hot days in late spring.. The fact that my ceilings never fell in on me is thanks to the excellant job the insulation contractor did when he wrapped the inside of the house with a poly vapor barrier. Even the seems were sealed and that was over 19 years ago probably 20 to 25 since the insulation contractor did his thing..
i don't know how to break this to you... but the moisture in your attic DOES NOT COME FROM THE EXTERIOR..
don't gimme the "i live by a lake".. i live by a freakin ocean... people install air conditioning not to get cool... they install it to keep the mold from growing in their closets.. you could wring the air out if you could get a hold on it...
so you have no different conditions than we do... except in length of winter.. and slightly lower temperatures...
wether your attic is vented or it ain't vented.. any moisture soaking your attic insulation can ONLY come from one of two sources.... either a leaky roof.. or warm moist air FROM THE INSIDE OF YOUR HOUSE
do you have a leaky roof ?
do you have ice dams ?
that only leaves one other source.....
can we say "inside your house" , boys and girls ?
if fredl was here , he'd have you testing with smoke candles and blower doors... and a poly vapor barrier you installed 15 - 20 years ago ain't gonna cut itMike Smith Rhode Island : Design / Build / Repair / Restore
Well Mike,
a smoke door will have a good laugh since about 3/4 of the house is SIPs and the other chunk is the old ground up paper. (I'm in middle of changing this from a stick built house to the timberframe covered with SIP's) so it is totally acidemic.
I am afraid there is a world of differance from living on the ocean (lucky you) to living in this frozen tundra.. Unless you get periods where it drops to 20 below for a week or more I'm afraid we are talking apples and oranges.. Unless you have a foot of snow on your roof much of the year (one of the reasons part of my house has a 27/12 pitch) I suspect that your micro climate is differant han mine..
IN some parts of the frozen North they claim that you should close up the roof vents for the winter.. I've often heard those same claims.. IN the case I outlined it would make sense..
yet I keep repeating myself, with that low of humidity in the house most of the winter where would the moisture come from? If you want proof of how dry it is here, please come and look at my wife's skin..
Mike,
I was driving home yesterday and noticed a water tower.. on the bottom of the water tower,... frost! Then I remembered that on occasion during the winter I've even seen ice build up on the bottom side of water towers..
Now it doesn't happen all of the time, but it does happen.. I'm certain that on warm days with the sun shining the frost or even ice melts and drops to the ground below..
Edited 1/1/2004 1:52:32 PM ET by frenchy
let's hope your attic is not a water tower..
or a fishing boat on the north atlantic..
your attic is an attic.. and the moisture is not comming from the outsideMike Smith Rhode Island : Design / Build / Repair / Restore
OK if the moisture is not coming from the outside, and water towers frost over in the winter plus it's desert dry in the house, where is this moisture coming from.. please don't repeat but only suspect. (that it's coming from this damp basement (that isn't damp) or leaks in the vapor barrier (that showed no signs of leakage as I took it down)
Mike, I'm certainly willing to admit that the old house was far from perfect, it had too many flaws to deny that.. however there were three things done really right (they must have been done professionally since so much of the rest of this house was so poorly done) the foundation was excellant.. the wiring was as fine as I've ever seen and the vapor barrier was very nicely and completely done.. the only penetrations I noted in the vapor barrier were for the waste water drain, the water heater flue and the chimney.
the vapor barrier was 5 or 6 mil poly with the seams taped.
well... i'm starting to sound like a nag at this point... and that is not my intention..
i find it hard to conceive that your soaking wet insulation was a result of moisture comming in thru the soffit vents..
and .. apparently the condition no longer exists.. you've changed it. so?
BUT.. on the off chance that it hasn't changed, but it's just moved out of sight.. i'd do some smoke candle testing and some blower door testing..
we spent 15 years installing 6 mil vapor barriers and taping the seams.. and we were really careful.. my own house has it.. i wouldn't trust it worth a plug nickel..
there are so many paths for air to move in a house.. thru a wall, and thru a ceiling.. the only way you know if you've got it sealed is to test it
if you don't test it.. then you have to use a system that isn't dependent on vapor barriers.. like sprayed in place foam.. or dens-pak in open stud bays.. ie: a complete visual inspection of every square inch of wall & ceiling..
fiberglass batts & poly film do not give you that visual inspection.. no wayMike Smith Rhode Island : Design / Build / Repair / Restore
Frenchy
That 5% RH air at 70 F that leaks out of the house into the atic will be 100% RH at 0 F. It will condense and form frost.
Something tells me that he doesn't want to be bothered with facts like that.
:).
Excellence is its own reward!
"Something tells me that he doesn't want to be bothered with facts like that."
I am SOOOOOO tempted to make a polictical comment here, but for once in my life I will behave.
Actually I think that it is more that he is not comprehending the physics behind this.
Frenchy, I have never seen triple digit relative humidity...it must be damper than damp.
The guys here have given all the possible / logical reasons for the tropical forest you have in your attic. Unless a leaky roof or an open combustion flue in the attic or a dryer vent under a soffit vent, the moisture is coming from the house carried in a warm air stream. It could be through walls from a crawl space, light cans, pull down steps, attic fan housing etc.
Re: sealing gable vents. I know an engineer who thought too much hot air was escaping his house in the winter, so he put plastic over the gable vents. The roof rained into his insulation/sheetrock within two days, yet he felt the house humidity was low.Energy Consultant and author of Practical Energy Cost Reduction for the Home
fog or a cloud has 100% humidity and that's triple didgets so Unless you've lived in a desert all of your life ;-)
Anyway on foggy days in the winter there is a lot of moisture in the air.. that moisture will go anyplace the rest of the outside air can go. it will enter at the eves and leave thru the vents.
This old house had relatively shallow roofs. They hold a snow load thru much of the winter particularly on the north side. Moist air from the fog and melting snow enters the attic thru the eves, comes in contact with the cold underside of the roof and frost is formed..
At some point the warm air escaping from the 70 degree house below will warm up that frost and it will melt.. when it does, the melted frost (now in the form of water) will need to go someplace.. reason says that it will fall on the insulation below. when water falls on insulation doesn't it get that insulation wet?
Please show me the flaw in my logic..
You and others have assumed that it can only come from moist air escaping from below.. Let me state clearly that within the scope of that arguement you and others are correct. However I have given you a clear method that will also satisfy the physics of thermodynamics..
It may not be your experiance, but unless someone can refute my arguement regarding how it happed in my home you must admit that it is not the only way insulation can get damp..
Regarding the sealing of vents. I dismissed that idea well over a decade ago based on articles in Fine Home Building.. I do know that in some parts of northern Canada it is common practice..
here's what's wrong with your example..
<<<<<< This old house had relatively shallow roofs. They hold a snow load thru much of the winter particularly on the north side. Moist air from the fog and melting snow enters the attic thru the eves, comes in contact with the cold underside of the roof and frost is formed.. >>>
those two conditions do not exist at the same time often enough to do what you claim..
in other words.. if it's foggy, then the temp. is above freezing and if it's cold enough for frost to form on the underside of your roof, then it's not foggy
there may be momentary times of short duration when these could occur... but not to where it soaks the insualtion..
if you have vents that are letting in that much air.. they may also be letting in fine blown snow.. i have seen two foot snow drifts in attics right underneath gable end vents.. and it sounds like you are describing gable end vents..
again.. this is a rare occurence.. if you have a continuing problem.. then the house is probably still the source of the moistureMike Smith Rhode Island : Design / Build / Repair / Restore
Mike,
well thought out, except that the snow mass on the roof will hold it's cold even though it may be above freezing.. (kind of the principle behind cold plates) so even with the outside air at say 40 degrees the bottom of the roof will be at less than that number, below freezing.. (I never checked, just noticed the frost) last week we had three days that qualified for that condition (warm enough during the day to melt stuff yet cold enough so some roofs still had snow on them.) once the insulation gets damp there really isn't a way for it to dry out.. the temp in the attic will be around that of the outside air..
by the way there were no gable end vents in the roof.. the air entered in the eves and exited from those roof vents (there were probably too few of those for good ventilation, plus under some conditions the snow would block them off..)
good point about snow coming from the roof vents,, very possible except that the bottom of the roof deck was frosted, sometimes very heavy and sometimes only the tips of the nail heads (from the shingles) that poked thru.. yeh, a lot of the time there wasn't any frost.. I have to admit I didn't poke my head up thru the attic access very often.. because I hated to waste heat I always kept it well sealed.. My observations occured over a 18 year period some winters I never looked and other winters I might look once or twice.. There wasn't anything up there, no storage or anything so only couriosity caused me to look..
Frenchy and Mike, I happen to think that both of you are right even though both of keep saying the other is wrong.
Frenchy has an under-roof microclimate that is freezing when the outside temps are relatively high with high humidity and the ice cold roof venting space is pulling warm moist outside air down the inside of the roof from the upper vents to the eave vents.
Mike, leave a crack in your freezer door. (|:>) Feel the cold air flowing out the bottom of the door? Give it an hour and you will see frost in the freezer. Even with a warm, tightly capped soda bottle full of water in the freezer.
Frenchy, seal a large square of plastic down to the basement floor next cold snap, and put a cake pan filled with crushed, salted ice. Check under the plastic just before all the ice in the pan melts. I'll bet you a beer in the tavern that you will see signs of moisture. Or freeze that soda bottle I mentioned to Mike and set it on the kitchen counter and watch the dew form.
So. . . why can't you both be right??????
SamT
Simply because that wouldn't be any fun! I get to expound on my thoerys and Mike gets to do the same on his.. If you notice we are being very civilized about it, hardlya single curse word or obsciene jesture involved! Probably should have gone to the tavern with this a long time ago but what the heck! Hopefully the Tauton press proprity police are on vacation.. ;-)
c'mon, frenchy... sam's gotta have his fun too... so shut up and take it like a man....
BTW... when r u gonna learn how to use that digital camera so you can illustrate some of these situations ?Mike Smith Rhode Island : Design / Build / Repair / Restore
I can take pictures, I can even print them out.. but to convince this stupid computer to post them so you can see what I'm describing is beyond my limited ability. Somebody please come over here and show me what I'm doing wrong? Please! grovel, grovel, beg, plead, whine!
By the way I went back to the store where I bought the camera and explained my problem he said,
you take ;wmpwe ;le and click onthe psk skjh wiv a pIh p p p phpqqrlskb>r qb.q. then you /ahcu; f/r ; ;ao ; ;rucpz.mv anfnf,fnma lqll oh ou o o ou <wab don't forget that lsv; sj b b mns,gn js lv ljll . .,j vonf;fa;bfap; v aap
wait while tpioe pthu psu;sph p hphpv and that's all there is to it!
Frenchy,
How are you finding your pictures on your computor? I mean, how do you know where they are stored?
What program are you using to look at your pictures?
What program are you using to print your pictures?
Do you have any image editors?
What do the names of your pictures look like on your computor? something like picname.XXX? what is the XXX in your picture names?
SamT
Edited 1/2/2004 4:51:20 PM ET by SamT
I shouldn't be sarcastic in a forum. Yes, rain and fog will produce 100% rel humidity, hopefully not in your house. Do you suppose snow is blocking the ridge vent (low pitch roof), and you are getting poor ventilation of house generated humid air with its subsequent condensation under the roof deck?
I agree once the cycle has started, the insulation degrades in R value, so more heat is lost, more condensation, internal rain etc. If that is the case, the attic needs better ventilation if you can't stop the humid source and path. PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
I didn't have ridge vents, I had a couple (yeh I know too few) of those box type vents, but yes I'm almost certain that was the kind of situation that happened. Some moisture condensed on the bottom side of the roof, melted and dropped onto the insulation causing further heat loss aggrivating the situation..
I suppose that the roof was about an 8/12 pitch before (front and back were differant and the back had this 3/12 pitch leading into about a 10/ 12 pitch.. {guestimate since that part of the roof is now in a landfill})
hopefully you realised the little smiley face was ment to convey a sense of humor about it..
the new house will be ever so much more efficent in regards to ventilation.. Have you got any data regarding SIP's?
The issue is cold roof VS hot roof.. In that a significant chunk of this house will have what is a "hot" roof. Hopefully with an R50 rating and as steep as it is (27/12 over the west wing and 17/ 12 over the great room).. it shouldn't become a problem but it would be nice to get some confirmation..
just as a little side note, the ridge of the 27/ pitch has 32 inches of foam from peak to ceiling and the 17/12 has over 18 inches at the ridge..
I don't have any specific info on sips, but a google search or direct contact to a manufacturer should provide pleanty. My take on them is that they are very effective as long as installation/seams are air tight.
There is a house somewhere in Oregon that was panel built with an ACH of .07, or one air change every 14 hours. This is a little extreme, but with an HRV, it must be pretty cheap to condition. I'll take too tight any day, and ventilate to my needs.
What kind of foam do you have that is 32" deep?
How are you ventilating those steep roofs?
PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
I had custom made foam panels made that were shaped to the roof and thus I wound up with that much foam at the peak!
as for the manufacter they assure me that It's OK not to ventilate the roof. (another words I can put the roofing directly on the OSB) that will lead to a hot roof which is a concern but not according to the manufactorer and several shingle companies.. (not all but there were several that were willing to extend their warranties in this application.. )
actually what I did was to use a layer of ice and water over the whole roof and then put a layer of cedar breather under the cedar shakes (handsplits) That apparently satisfies the shake manufactorer... although with a ten year warrantee I doubt he has his neck stuck out too far esp. since these appear to be old growth cedar shakes.. unbelieavably tight rings indicating extremely slow growth common with old growth.
as for too tight, I agree with you and did every trick that I ever read about to seal this house up tight. Any suggestions on brand of HRV?
Hey frenchy I'm trying to picture you nailing those shakes on a 27 / 12 roof
does that cedar breather have lines on it or do you lap it like felt at the exposure you want or did you nail on a temporary cleat and drop the butts to it?
What exposure did you use? what bevel for ridge? I'm wincing as I imagine the hammerclaw indentations on my forehead
way back when I planted many a doug fir on slopes about that steep
John,
nailing shingles on the 27/12 roof was a piece of cake.. I used a telescopic fork lift with a work platform on it and it was like shingleing a wall.. lean over and nail in place.. shakes right there at my side (I even got lazy and used a table so that they were always in easy reach and I didn't have to bend over to pick them up..) when I ran out of nails, shakes or whatever I'd just have my wife lower me down so I could reload.. it took about a minute or so to lower me and about the same to lift me into place.. I always was working between waist and shoulder height, never over or under since it was so easy to raise me up or lower me.. so I can't imagine an easier way to do things.
When we rented out all of the forklifts I used a manlift. with the forklift I needed to have my daughter or wife run me up and down however with the manlift I was able to operate the controls from the basket so I didn't need anybody. With the work platform I had a 4x16 foot platform to work off of, the one I used was returned without the required railings so it was actually easier to use, not having to reach around the railings (I was carefull that I paid attention to my footing since I didn't want to take a 40 foot first step,.. railings would have eliminated that concern but still you could feel the ridge of the edge of the platform so I didn't feel frightened.. (don't do this this at home kids, do as I say not as I did!) I did set the platform right next to the roof so the only way to step off was on the sides or the back since I stacked the shakes back there and kept tools like hammers, trim saws, etc. there, only the sides were an issue..
I used 8 inch exposure and the roof came out perfectly with 8 inch exposure at the ridge.. As for the ridge I used custom bent 20 gauge copper as my ridge (or will once I do the back side)
cedar breather is like a plastic version of steel wool with 1/4 inch bumps in it kinda like a golf ball in reverse. you don't overlap it you butt it together.
I used a 1x1 black walnut cleat to set the butts on but I screwed it in place rather than nail it.. seemed to be a lot more steady and with a bit in the electric drill it only took a second and it was easier to get dead-nuts right on.. I used one set of screws so far running them in a bit and then backing them out..
one corner of the roof I did have to use roof brackets and that was tough! I really respect those who day in and day climb up on those things dragging bundles of shakes up with them and doing roofs.. I was even able to cheat and raise the bundles up to the scaffold with the forklift so I didn't need to bust my butt doing that part..
luckily it was only a couple of bundles to do the part that need to be done off of toe boards. There will be a section towards the lake that will be done off of toe boards (roof brakets) but that's a mere 17/12 pitch and if I should slip, there will be scaffolding under me again..
Edited 1/1/2004 1:48:44 PM ET by frenchy
Edited 1/1/2004 1:54:06 PM ET by frenchy
Frenchy, I have not personally owned a HRV, so I would defer to some of the guys who have, to advise you. I have read the lit on some, like Fantech. David Thomas has some interesting experience and innovations in his HRV. Many threads have discussed HRV.
I built an air injection system with triple filtration to keep positive air pressure in the house during spring/fall pollen season, but it does not have heat/cool capture.It does keep air flow pushing out on a still day, and has greatly helped reduce allergy problems. The neg pressure gas appliances have dedicated/isolated outside air...clothes dryer, water heater.
You seem dedicated to getting all the "squeal out of the pig".
Have you looked into a GFX, or is drainage plumbing out of reach?
Glad you have house well sealed. The old "non insulated " vacuum thermos bottle did fine with its vacuum/radiant coating. PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
GFX? what's that?
I keep listening for information on HRV's but so far there doesn't seem to be any real agreement as to brands etc..
so if i am understanding correctly you are an advocate of site sprayed foam with no attic ventilation? would this also apply to a crawl space? and what would be the extent of the climate ranges you would advocate this system for? this is what i think is best, and hope you agree with me, based on what i have learned from reading just recently(tauntons book on weatherizing and insulating, the pro series, excellent book)
there appears to be a debate, some question as to what is the best insulation system. i think frenchy's problem is solved with a spray in urethane, that will seal the air leaks. mike does not favor foam, but insists that air leaks are the culprit for wet insulation in the attic, is not spray foam the easiest way to seal the air/vapor from living space to attic?
i keep hearing paul advocate a combination of site sprayed foam, and batts? does it not make sense to just fill the space with spray in foam while you are there? one would assume that a large part of the cost of site sprayed is the setup/cleanup/breakdown of highly specialized expensive equipment, and with time being money in most cases isn't having the insulation/sealing/air/vapor barrier done in one day a more cost effective way of insulating a new construction structure/home? would the money you save by not filling the space with foam pay for a different crew with different materials to come out, set up, and finish the job? if i was an insulation contractor i would keep my spray unit spraying, and nothing else, i would have a different crew entirely for batts etc.
I am an advocate of urethene faom, sprayed in place. With this system, ventilation is not alwys necessary. I don't take permanent sides in the ventilation wars. it depends on the house. In new construction job, you can design and controll the whole thing, but with remo work, you are generally dealing wioth only a portion of the structuir so compromises sometimes need to be made.
I've never had a problem with urethene and it gives me good reviews with my customers, most of whom can afford the big price tag up front.
Mike has no probs with cellulose in his jobs.
I have seen old houses filled with cells that developed moisture and moild problems.
The principles involved in this whole thing are that either you need to provide ventilation, or you need to absolutely control everything. A spray faom or a denspacked cellulose job - either one can be done so as to eliminate the dewpoint anbd stop condensation issues. SIPs can too when installed right.
But then you can end up with stale damp interior air too. Enter HRUs.
I'll have to let Paul explain his hybrid design. In my understanding from his posts, he is attempting to get the tight seal from the minimal spray and finish the R-value buildup in ways to reduce costs. my customers generally cen handle the cost so I don't look for that compromise. I don't endorse or attempt to disprove Paul's methods as I haven't seen them in action. I am like you in finding a redundancy of labor in the installation of multiple methods that seems inefficient..
Excellence is its own reward!
Skids and Piffin, Happy New Year. Re foam and fg combo.
The combo accomplishes a good cost /value of excellant sealing and R-value. Take a 2x6 wall and put in 2" (R-14) of foam (closed cell poly)followed by typically the same contractor on the same day putting in R-15 batt (3 1/2"), same job foreman.With sheathing, wallboard etc., you have a well sealed wall at R-30, and the fg is able to perform with out air flow problems. The total installation will be $0.85 to $1.00 per sq ft less than 5" of foam yielding R-35 + sheathing.
Both a major installer and the manufacturer agree that that is the most cost effective package. Both would make more profit with a full 5" of foam, but my questions to them were "what is best bang for buck,...or, what would you do for your own home?" There is one potential problem that can occur with full depth foam. Today's often less than dry wood can hold enough moisture that can get forced out of the wood during the exothermic heat cure of the foam, thus preventing deep spray (over 2") jobs from good adhesion to the studs.
Wet sprayed cellulose gives good air sealing, takes special equipment, yields 3.5/inch R-val.and requires a drying period. Dollar for dollar, I keep coming back to the foam/fg combo. I think each person should price the total application in his own area on a cost per R/val/ air seal comparison.
If additional R-val is needed, or a need to break the stud cross section thermal transfer, then I would add a layer of foil faced foam board exterior of the sheathing plywood/osb. If an air gap is then left open (like prior to brick), the wall will have a good radiant barrier as well. I offer this as just my opinion as to what I would do, and hope it is helpful to others. PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
paul... we've done lots of 1" polyiso on the exterior for a thermal break..
no more for me...we've opened up too many walls with the foam loaded with vermin..
the only foam we'll use on the exterior or interior of a WALL is treated foam.. and the only one we've found so far is PerformGuard.. EPS treated with borates..
if we want the extra R-value, we install the EPS on the interior and strap the wall horizontally...
but with a 2x4/2x2 Mooney wall we can get a nominal R-17 with just cells
have you used any of the dens-pak blown thru InsulMesh? this doesn't require special equipment.. and you can get 3.5 to 4.0 lb/cf density with dry cellulose
Mike Smith Rhode Island : Design / Build / Repair / Restore
Mike, I have not used the mesh/dry cell system, but it sounds like it is pretty good. How is cost vs closed cell? I do like the "glue" effect with foam for max sealing. I am aware of one contractor who has done a number of homes with 1" sprayed foam followed by wet cells. R-15-16 pretty tough wall. However, that did require two different power trucks, and foam/fg only requires one.
Please don't get me wrong re cellulose, it is a huge advance over fg batt, roll and blown. I will use 1" spray foam on attic floor, air boots, ductwork, drop ceilings etc., and then fill with cells which will "snowdrift" over any trunk lines.
Re; the foam board. Is perform guard available with foil on one side? I want a good radiant barrier on walls behind brick. Have you found vermin in foam board with aluminum taped seams and edges?
If you used a foam board with foil, would you prefer felt paper on the sheathing or tyvek type product?( would like to have a good air barrier product that had low emissivity, an aluminumized tyvek...) Paul
edit :I was in a $$million house under construction last week in Dallas. A lot of foam in walls, even some in the attic. I was impressed with the care some contractor was taking until I found three layers of 6" fg batt stacked in some areas of the attic. Each layer had a vapor barrier....Also, all attic duct work (three systems) hanging from roof rafters. Hundreds of feet carrying coldest air through hottest portion of the house with lowest R-value insulation. Stud bays used for returns, but voids through back walls not sealed. 1/2" gaps around ceiling duct boots and sheet rock allowing air blast back into attic. Price just doesn't mean good work. PH
Energy Consultant and author of Practical Energy Cost Reduction for the Home
Edited 1/2/2004 8:22:03 PM ET by Paul Hayden
paul... when we were using foil faced, we never taped the edges not the seams... but even if we had the vermin would still be there.. every knife cut, every nail.. every pipe would give them access..
as to comparative costs of foam- in- place vs. mesh & dens-pak.. i don't have those numbers.. it's been about 10 years since i got a quote for foam-in-place.. has it gotten any cheaper ?
i "think" it's gotten more.. a lot of the foam guys got burned with the old bugaboo about outgassing remember that ?
anyways .. the mesh is labor intense... staple & glue the mesh.... then next day blow the cells... blowing goes fast.. the staple & glue is slow... but so is everything else..
my numbers are at the office so i don't have anything to offer as to cost
if you want more info on the insul mesh.. google on Regal Wall.. a big insulation supplier in Ohio i think...
we've been doing it for about two years now.. i learned about it from someone here .. i think thye were out of Arkansas.. ( not tim mooney )
PerformGuard.. i can get it with just about anything... blueboard.. osb... drywall.. i've never ordered it with foil.. but i bet they do it...Mike Smith Rhode Island : Design / Build / Repair / Restore
Mike,
I'd like to pick your brain about you "Mooney" wall.
First, what is your typical board foot cost for the cell (lineal foot cost with 5" Mooney and 8' height would work too).
Now how long would you estimate it takes to strap and staple the mesh on. I know you strap ceilings anyways, but I can't remember if you like to do the walls also. If you would, then the labor/material cost for the strapping is irrelevant.
Now, I wonder how this compares to the two prices of foam that were mentioned ($.35/bd. ft. and $.7/bd. ft.).
Two advantages that I can see are that you significantly reduce the thermal bridging and the strapping could come in handy (as long as you know it's there)... Nail trim anywhere, fasten cabinets anywhere, etc. Of course, the thermal bridge could be dealt just as effectively with 1" EPS on the exterior over the ply, but you've shared your lack of affinity for that method.
I guess I'm just trying to determine the cost of keeping foam off of the exterior. That would kill the bridge, then you could insulate with whatever method you choose.
What do you think?
Jon Blakemore
i am currently working on a plan with steel stud construction. the method of eliminating thermal bridging is a 1" gap between dual exterior walls. everything will be tied together by plywood cleats-windows, doors, etc. the plan calls for steel joists and scissor trusses as well. the subfloor will only be installed after the dual exterior walls, with a similar dropped ceiling so as to isolate thermal bridging there as well. i think with this method i have eliminated the problems paul describes with over applying foam and having it pull away from wood. supposedly the foam is a better combination with the steel, and eliminates much of the dead space of wood frame headers and corners.
there is a company in so cal that another contractor in my area uses for wall panels. he orders, and they prefab and deliver onsite. i will fabricate my own floor panels and trusses onsite, as i have yet to find a manufacturer to build these, although i may yet come up with someone. the idea is to work the bugs out of this system and put together a package that can then be sold as a kit house(framing package), only custom made to whatever plan is desired. the goal is to get something that even an apprentice (simple) can put together with screws. the screws act as clamps for the welder, and stay in. prefab sections will be color coded with spray paint to indicate where welds are required, and make for an easy way to check off on welding for inspector. steel frame sections are very light and easily moved and installed by 3 man crew without equipment, you screw together framing package, and call out the welder to glue it in place.
my favorite part of the system is the foundation, which will utilize prefabricated steel stud wall sections instead of rebar and protruding above the concrete pour to eliminate the foundation connection of structure at the concrete level. the prefab sections are screwed together in the trench then anchored and braced so as not to move around while concrete is poured. forms for concrete are attached to the pony wall following grade, and removed after pour. concrete is finished with a shovel as it is never seen and doesn't need to be flat for a wall instalation. it could even be done with balloon frame walls and welded joists for floors, but i'm thinking the standard method of stacking joists on pony foundation wall is more efficient.
i'm trying for an extremely simple system to assemble onsite, that anyone can put together, and then call in the specialists to weld, and spray the foam, for a super strong, super insulated, termite, and mold proof house. the future of construction as i see it.
Be sure there is no oil on the steel studs. You will have most of the wall foamed, ie., a higher percentage than 80 due to the channel being filled, and stiffness should be great with closed cell.
I know this has been brought up before, but what is the best way of attaching tall base board to the sheetrock when using steel studs?
Please keep us posted on your efforts. PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
paul.. my best practise for tall baseboard with steel studs is to put plywood blocking between the studs... notch the "C" side and attach , let the no-flange side float..
catch the no-flange side with a screw thru the sheetrock.. now you have all the blocking you need for the baseboard, and you've made a minor compromise of your insulation depthMike Smith Rhode Island : Design / Build / Repair / Restore
Mike, thank you, I understand. Just wouldn't want to glue it.
What about starting the sheetrock about 3" above floor, and straping in some long strips of 1/2" plywood across the studs. Then, 4" base would cover the seam (I would want it taped anyway) between the rock and the ply? That would avoid the stud cutting. You have probably already tried this and figured the individual blocks work well. I have not built with steel studs, but may consider for next personal house. PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
paul... your's is probably even better ... we do throw a lot of blocking in when we work with steel studsMike Smith Rhode Island : Design / Build / Repair / Restore
Mike, do you think it would work for chair rail and crown molding as well? The rockers shouldn't object if the framer placed the strapping where trim had to have nailable support, and the studs would pick up some support. PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
well.. it would work... but a STRIP of plywood will lay a little differently in the middle of the wall ( chair rail ht.) you may get some bulges you don't want..
i like blocking behind the drywall ( blueboard for us ) so the drywall is continuous and as big a sheet as possible..
your strip would probably work.. but your options would be limited after thatMike Smith Rhode Island : Design / Build / Repair / Restore
Mike:
Thanks for the reply. Pretty scarey story, particurally since the problems surfaced in a short period of time. I'll definately remember your recomdation for Perfomguard EPS for sheathing.Matt
OK Paul, if these guys can pick at each other, let me a turn at your theory/method to see what you say. You have obviously done more cost analysis and comparisons on the numbers, but for me, that would vary due to local conditions. In many places, the spray foam guy is one sub and the cell/fibre guy is another sub so more co-ordination and potential delays follow...it almost compares to hiring one sub to run tarpaper and flashings on the roof and another to lay the shingles. Who do ya call when it leaks?
First thing that stands out is to ask about those cost comparisons with the 6" wall cavity. Do they take into account the extra cost of lumber for the thicker wall?.
I also note you seem to be comparing the R30 combo method to R35 of sprayed foam. Why not compare costs of equal R-vaules? Also, I'm thinking that if you wanted that much R-value, you could get it from foam in a 3.5" studwall. let's see, R7.2 x 3.5"= 25.2 OK Not quite. but close. I can't really see why anybody would need more than that in a WALL.
The other thing that raises questions in my mind on this is vapour barriers. In the wall system you describe do you rely on the single foam for vapour stop or let the fibreglas guys lay another inside the studs? Normally you never want a double VB.
.
Excellence is its own reward!
I can help with costs a bit..
In general it costs about $400 dollars to get the foam truck out to your place.. (that's kinda the fixed cost. then they charge about 35 cents a sq.ft. to spray foam.. do a rough calculation of the space involed and you should have an idea of the costs.. *
By the way this months issue of Fine Homebuilding has a great section on insulation. you really should buy it and check it out.. your questions are pretty much answered..
* length (in inches) times height (in inches) times depth (in inches) then multiply that number by .80 (roughly the percentage of wood that occupies a wall the rest is available for insulation).. and divide the whole mess by 144 that is the number of sq. ft. multiply that times 35 cents or whatever the local charge is and add the $400 fee to get the truck there..
walls that have windows subtract them if they are big or a lot of them and don't forget to subtract the space where the header over the window is.. there isn't any insulation there either..
granted the numbers are rough but everybody needs a starting point..
Edited 1/2/2004 10:43:11 PM ET by frenchy
I know about the minimum 400. That's the same here because of setup and parts for the equipment that wears and is throwaways.
but my installed cost is closer to seventy ccents a board foot here. i've never done one small enough to worry about the minimumfee..
Excellence is its own reward!
Everybody seems to be talking about spray foam in a generic sense, when, in fact there are a number of different products that have very different properties and costs. From the less expensive products that are maybe .5 PCF and have a perm rating of maybe 15 and a R-value of 3.5 per inch all the way up to the top of the line type stuff like Piffin mentions (Corbond - not sold in my part of the country) that is maybe 1.8 PCF, ~7 R-value/inch thickness and a perm rating of around 1.
Specifically what product were you talking about that is $400 setup fee + $.35/sq ft? Also, If I read your correctly, then you are talking about $1 a sq.ft. for a 3" thick application?
Mike Smith - you say that your major objection against foam is "vermin" by which I assume you mean insects. Not doubting you one bit, but just curious as to your opinion as to why "vermin" like foam?
Matt
Edited 1/4/2004 12:15:41 PM ET by DIRISHINME
irish where i live there are all kinds of bugs, and everywhere i look they are crawling into crevices and under boards and rocks. they seem to love to hide for some reason, even if there is nothing to eat. must be some instinctual craving for shelter i guess. its a county wide thing too, you can't put a 2x4 down for more than a couple hours without there being a bunch of pincher bugs under it, not to mention the pill bugs, silverfish, spiders, and ants. oh and the termites those things will eat concrete i swear, or at least tunnel through it.
i too am anxiously awaiting information about the different types of foam, i very much want to use it, but want to know more about it. which is best for where and why? seems to me the spray rig is pretty much typical as a piece of equipment, but different blends of ingredients yield different foams. i am thinking the best is a closed cell non-permeable for mixed climates-not too cold or hot-medium humidity, with an additive of borates to discourage vermin?
Some foam manufactorers are using borate in their process. it's harmless to humans but kills bugs... one of the reasons I chose AFM
What is AFM? - a SIP manafacturer?Matt
yes
The 400 setup minimum gets mentioned to me by both of the foam sprayers I have mentioned. It could be that frenchy knows people who charge 400 plus .35/board foot while mine charge .70/bd ft with a minimum of 400. His pricing structure would be much better for bigger jobs. My subs have an island ferry transportation system to deal with in their pricing too.
Insects don't eat the foam, but it makes excellent nesting material that is easier to burrow into than wood is.
Termites like to eat wood but all the others only burrow in for transport and nesting. The reason they cause problems in wood structures is that they carry moisture, spores, fungi, and bacteria with them that take a turn on the wood.
When any insect ingests borates, whether from chewing a tunnel or eating outright, it destroys their gut so they die of indigestion and starvation..
Excellence is its own reward!
matt... can you imagine doing work for a lawyer .. encasing his whole house in foil faced 1" polyiso.. ?
then comming back 3 years later to install a window in a 2d floor wall ?
when we cut in .. the 1st quarter inch under the foil was litterally honeycombed with a bug that neither one of us have ever identified...probably the larvae period of Godzilla..
i also know from personal observation that termites love foam on the foundation.. it's the space age version of their old mud tunnels..
then you get to carpenter ants.... we built on on top of a hill in a pine forest... wrapped all the 2x4 studs with 1" foil-faced polyiso.. solid blocking for nailing.. and 1/2" sheathing for a nailbase..
just before plaster the owners and I were doing a walk-thru.. and i heard an owful grinding sound in a 2d floor bedroom... pulled back the fiberglass batt ( yeah , i know... fiberglass... hey , what'd i no ? )... pulled out my McGiver tool and cut out a little square of the foam.. 1/2" carpenter ants came pouring out... man .. freaked me out.. luckily i had mentioned to the owners that they should have bug people spray their foundation ..
so they did.. and signed up for their maintenance contract
when i found out i could get everything i wanted from EPS , including borates.. i vowed to never allow foam in my houses again unless the mfr. had ADDRESSED the bug issue..
know what's a huge laugh ?
our statewide interpretation of the energy code allows for external application of foam to the outside of foundations..
.because of the bugs.. they also allow it to be cut flush with the grade line so there is no foam from the ground up ????????????
so they get earth sheltered foam from the relatively warm ground down... but zero protection from there to the sill in the coldest zone on the house.... Mike Smith Rhode Island : Design / Build / Repair / Restore
Piffin,
The insulation contractors I have dealt with in a number of places all started with fg, and then went to cells or foam. They still do the fg and either cells or foam, so one company gets the whole job. Also have a number of people who want to do some DIY work, and do the finish fg or attic cells themselves, after a wall partial foam job.
Re 6" wall... was not trying to compare 6" to any other thickness or cost of structure, 2x6 vs 2x4. Example was for how a 2x6 one way vs 2x6 another way. My contacts only claim R-7 for closed cell, and even in a 2x4 wall, they try to hold to 3" to avoid too much over expansion that has to be cut off (more labor cost). Result is r-21. However, in earlier post I explained some problems they have experienced with over 2" foam spray. In a 2x4 wall, 1" foam plus compressed fg for remainder can produce a good package at R-13-14. Cells can fill the full 3 1/2'' at 3.5 for r-12.25, or go cheap to full fg using the 3 1/2" commercial batt that has r-15. In those comparisons, my preference is the foam/fg combo, followed by the full cells. Full fg batt is not an option for me.
Re wall R-value.Some people in very hot or cold climates want to lower their initial heating/cooling equipment cost (as you well know) and to have low operating costs. They pay big bucks to get a few extra Rs for their windows, and want high R-value walls as well. Others, want stronger walls, ie full plywood sheathing on 2x6 studs, or even steel studs. I will be the first to admit, I will lean to over design rather than under, but then we can't predict the energy cost for very far out (like a month ). Did you notice in the FHB insulation wall article that plywood ,not osb, was recommended?
With closed cell foam, I am not recommending added vapor barriers,and have had no problems. I was able to see a complete back of house wall opened for an add-on recently, that had 1/2" +/- closed cell sprayed in 5 years ago (fg filled rest of cavity). Sheet rocker had insisted on glue/screw to guarantee no nail pops, thus no plastic on studs.Kraft backed batts were pressed in.I guess you could say that was a partial second barrier, but not one I would depend on. Exterior of sheathing had 1/4" fanfold, covered with tyvek, and then vinyl siding. Wall was perfectly dry in mixed climate region. Humidifiers were used in winter,od down to 0 deg, and summer od humidity was always high with 97-100 deg days requiring a lot of A/C. No evidence of moisture, mold etc. I believe air infiltration/movement the major cause of moisture problems in walls, not including mechanical leaks, and the gradual tempering of temperature gradiants with a good insulation package can prevent condensation if there is no air flow. Appreciate your input any time. PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
Wow, that last example actually had three (partial) layers of VB, something I would never let get by, but it shows that the excellent insulation job eliminated the dew points to overcome the liklyhood of trapped moistuyre, it looks like to me..
Excellence is its own reward!
Piffin, Re three layers of vapor barrier. What three are you counting? I see the foam spray as one, the paper backed fg as a "partial". The fanfold has small perforations throughout, and was not taped at the seams, and had a bunch of siding nail holes. I hear tyvek referred to as both a vapor barrier and an air barrier. A few years ago, it was only an "air barrier". Do you and others in the trade consider it to be a vapor barrier? I see it used entensively as the only barrier often between stone and osb, with irregular shapes of stone pressing against the sheathing wall. I wonder in time what will happen...
A question for all... How many of you have seen a moisture problem on an uninsulated band board above a kitchen ceiling, assuming no vapor barrier behind ceiling sheetrock? Wouldn't that be a guarantee of problem, ie., hot moist air rising in kitchen during turkey day cooking, only sheetrock keeping air from band board, cold outside air against board? I don't propose to not insulate the band board, I rec spray foam at least, but I have seen many houses with little or poorly placed or no insulation in the bays, and haven't seen any problems.
Just curious, not making a statement. PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
Yeah, I was counting the fanfold too..
Excellence is its own reward!
Piffin and Dave T if following this thread. Jump over to 38352.6 and tell me if this idea is crazy or not. Tks PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
For everyone else; Pauls http://forums.taunton.com/tp-breaktime/messages?msg=38352.6 .
For Paul;
Sounds like a good ides to me. Smart thinking ouside the box.
SamT
Thanks, Sam. Planning to build where sewer bill is 2x the water bill, so both conservation of water and heat are important. Figured this mix valve idea may kill two birds with one stone.
My master bath plumbing will look like a space ship. Radiant loop under floor for hot water on way to shower as well as heated towel rack, mix valve for water to toilet, GFX on shower drain water for cold line to shower.Would like to heat the lower 2 feet around base of tile in the shower to promote rapid drying/no mold. That should get most of the squeal out of the pig!
Does any body have experience with the new AO Smith Cyclone 94% efficiency water heater? Looking at it as well as Polaris and Bock as sources for domestic hw as well as rfh and heat exchanger in central air.
PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
Paul:
I am interested in your foam/fiberglass combo for my new house. The plan is 2x6 walls, drywall(perhaps plaster veneer instead), no vapor barrier, plywood sheathing, Tyvek, air space, brick. A few questions. I can find Icynene contractors locally, but not the other foam. That means 2" of foam would be ~R7, plus the R-13 of fiberglass at3 1/2" would get R-20 total. The FHB article suggests a couple layers of XPS outside the sheathing, but I don't think I could fit that in and leave an air space for my brick. Pouring wider foundations for more insulation might be overkill! What about moisture control? This is Northern Illinois, so the moisture gets pushed and pulled both directions depending on season. The Icynene provides an excellent air barrier, but is not a vapor barrier. The plywood sheathing, if not wet, would be considered a vapor barrier. Is something else needed? Kraft facing on the fiberglass or not? Any and all input appreciated.
Xman, Have you noticed that every article leaves the vapor barrier answer always open, never a definitive answer, especially for mixed climates which covers most of the USA. Someone once said, we need to move the vp with the seasons to be right all year. Well, we don't do that, and the 6 months out of sync are not rotting all the houses with a fixed vp, and my house in the mid-Atlantic region is not rotting and it was not built with a vp other than felt paper on the sheathing.
In my opinion, providing there are no mechanical water leaks, the movement of air is the most important aspect of vapor control, and good continuous insulation is the guardian against condensation.
A good read in addition to the FHB Jan 2004, is the FHB April/May 1994.
You are faced with the same question re. poured wall thickness cost vs what to put in the wall behind the brick, that I am facing. Where I will be building, a 10" pour requires one grid of rod, and over 10", ie.12", requires two grids of rod. Once I carry the sheathing to the sill plate (1/2" or 3/4"ply), the brick ledge space gets too tight if I put 1/2" foil faced foam board (something with borate, I trust Mike's advice) and then leave a 1/2" space for the radiant gap needed. I may look at thinner brick, or I have to go with a 12" pour.
Have you tried calling NCFI at 1-800-346-8229 and asked for closest installer to you for closed cell poly?
Here are some options we both can consider:
A. I want 2" of poly closed cell foam backed with 3 1/2 commercial R-15 fg batt, on a ply sheathing with over lapped felt and 1/2" BORATE treated foam foil faced board (foil out) air space, brick ties, brick. Total R-val, about (14+15+2)=31; no air flow, good rad barrier,some thermal break, strong construction, yadda, yadda....
( I am sure that will gather some commentary, note no tyvek included )
B. If you can't get closed cell, suggest you price full wall thickness of Icynene at 3.6 per inch= 19.8, vs full thickness of wet blown cells at 3.5/ inch=19, vs 2" of icynene backed by 3 1/2" fg. @ 7.2+15=22.2.
I wouldn't worry about the difference in R for those walls, as good installation/cost are more key.
It would be nice to add a foam board thermal break on the sheathing, and then tyvek for a moisture shield (rain screen,capillary break) before the air gap/brick tie, brick.
So where is the vapor barrier in the "B" options? You are in a heating zone, so past practice would be to place a barrier on the interior wall behind the sheet rock. That could be poly sheet, which precludes glue for the sheet rock, or flanged fg with the flanged stapled over the stud faces. I prefer glue/screw sheet rock, so I would side staple the fg flange.
Re poly sheet, I under stand the theory of a nice well detailed perfectly fitted continuous sheet on studs,top and bottom plates, no rips etc., But I don't see many installations that perfect in real world.
Without the fg, ie cellulose or open cell foam, you have at least two choices. Tape the seams of skinned foam board and foam all openings in the board, or put up the poly over the studs, if you intend on having ####dedicated vapor barrier. I would lean to the well sealed exterior foam board and glue the rock to the studs.You see why I come back to the closed cell poly foam for my first choice in sealing/vapor retarder. (note, people use the word "retarder" because it provides an escape from the word "barrier" or "proof")
Xman, sorry for the long answer. Are the systems perfect for all seasons, wind, humidity swings, rapid temp changes?"No". Are they reasonable approaches to a good wall for the variety of climate changes you and I experience?"I believe so". And,there are other approaches that will surface from the experienced guys on this forum.
What ever you decide, do it with attention to detail, and get the rest of the systems tight ie., ceilings, crawlspace, ductwork if included, sill seal, sole plate seal, dedicated air to combustion burners and clothes dryers...Then look into a heat recovery ventilation system to provide fresh air, but filtered air where you want and control it vs leaks all over the house. I know you understand that it is a total approach to the energy challenge. Hope this is helpful, Paul
Energy Consultant and author of Practical Energy Cost Reduction for the Home
Paul:
Thank you for that info-packed answer! I thought I was missing the discovery of some Rosetta Stone in my research, but it appears to be an inexact science. With a little digging, I did find some nearby close celled foam folks I will contact(Corbond). Back to the issue--I guess with the foam forming an interstitial vapor and air barrier, any other complete barrier is asking for trouble. As for the Tyvek, since it does not claim to be a vapor barrier, but only an air barrier, would it be needed? The foil faced boards would seem to do the trick. Speaking of, don't the brick ties defeat the seal? Won't you have to crush the board in way too many places? I'll have to talk to my builder about foundation thickness.
There is good info on ventilation at http://www.buildingscience.com , thanks to this forum for that link. They have great info on keeping air healthy while conserving energy.
Thanks again for an interesting and informative discussion.
if i am understanding correctly xman both you and paul are considering a brick veneer on top of wood framed and sheathed construction. i recently saw a product called "E-Z Rock" which is a concrete brick veneer wall system that hangs on light gauge steel hook hanger rails. i looked at their website and they say it is an excellent compliment to the styrafoam form concrete wall system and found myself wondering if it would be possible to use steel stud construction w/diagonal strapping instead of sheathing for shear, and then applying spray foam from inside without leaving an air space for the brick. with a borate added to foam to deter vermin, and a closed cell foam would an air space be neccesary? if you could eliminate air space wouldn't spray foam do a nice job of gluing brick to framing? am i nuts to think about stuff like this, why can't i just leave well enough alone and do it the way they been doing it all along?
Xman, As you can see from Corbond's specs, you reach 90% of its insulating value at 2-1/2 to 3", and under 1 perm., vs 6, 7".
I agree on the tyvek, but always like to have a water barrier to protect the ply, so I will use felt paper. Around lower band, will probably put an 18" wide strip of water/ice shield first, and mortar net or such to keep weep holes clear.
Re: nail or screw compression of foam board for brick ties, a long enough fastener does not have to flatten/crush the foam board. Just saw a three story poured (ICF) concrete mansion (Dallas) with foam exterior that had the brick ties nailed into the concrete. Couldn't find a crushed foam panel. Did find a number of bowed window openings, and if the foam wasn't treated, there may be bugs in the owners life in future. (foam from earth to roof, inside and out, Mike will scream). PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
Xman, please check you e-mail system status. My direct reply will not go through from either my e-mail or the forum e-mail. Your direct e-mail was received by me. Tks, PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
I've read all 105 posts in this thread and think I'm following everything but I want to be sure. My situation is a little different.
Existing, unfinished (ie. completed but no sheetrock) garage/workshop, Stick built, 22x35. 12 ft walls, 2/3 loft, 9/12 pitch with large gables and valleys, cathedral ceiling. It was designed to match proportions of a post and beam 1 1/2 story design. I was originally wondering how to vent the valleys for fg bats.
It sounds like the preferred solution would be to spray the underside with a vaporbarrier foam, (like corbond?) up to 3 inches max. With no venting of the valleys.
When I get around to adding sheetrock, fill the remaining space with fg bats, kraft faced and glue down the sheet rock, no plastic sheeting.
Is that it? What did I miss.
thanks
-justin
what part of the country are you in?
what is needed and required in one location can be a foolish waste in another (that's why there are so many heated converstations and absolutely sure comments here..)
What works in Minnesota could be a major mistake in Mississippi..
oops... Westchester County, NY, just north of NYC.
Out of my area, how about it are you out there Mike?
Justin, sorry to just now respond, been out of town.
Not sure of your configuration. If I understand, you are carrying the garage/workshop to the roof rafters,ie cathedral ceiling, and want to insulate between rafters and roof deck.
Where are you introducing out side air into the "room"? What spaces for air flow do you have in mind at the roof that are not cathedral, and will be open to the out doors? Do you have a picture or drawing?
I am trying to visualize where you want your sheetrock ceiling, any "attic" and any openings to the outside (soffits,gable vents or ridge vents), or any air space above ceilings and roof deck. Is this a free standing building, or an addition to a house? PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
That is correct. Here are a couple low res images. They give the basic idea. Right now the soffits are not vented until I figured out what I wanted to do. It has ridge vents. there are also plans to someday add a cuppola where the gables cross. There is about 3 feet of head room above the collar ties in the loft/gable area. The loft is open to the shop below. The side walls are a plywood sandwich with housewrap between, and battens over the seams.
Right now, the plan is just to make it a little easier to work out in the winter (hobby, not commercial). But I don't want to do anything that would create problems if the loft were converted to a rumpus room or office later.
Justin, that is a very nice looking garage/workshop. A cupola would look great as well.
You have at least two choices, probably more. I can't tell if the gable facing straight out in the pic has a ridge vent, nor can I see any gable vents on the end of the gables. I did see the main roof ridge vent.
A. You could install foam soffit venting baffles from soffit to the space above the collar ties in order to carry air from soffit to the ridge vents. I would then staple some kraft paper across the top of the collar ties (I don't know your spacing, may need to add ties or perpendicular strapping) in order to provide a backstop to receive sprayed foam.This has to be strong paper; I have used the foil/kraft with string scrim in the middle, and a lot of staples) Then, spray a closed cell poly foam against the baffles/kraft. This would give a tight foamed "ceiling " with air gap behind it.F/G the rest of the depth, and sheet rock, or add a layer of foam board to create a thermal break on the rafters, then sheet rock. With 2x6 rafters, you should be able to get R-30+, and very tightly sealed.
B. You could spray directly to the roof decking up to the collar ties, do the paper thing, carry the foam across and down the other side. Install a gable vent in each end of the building above the collar ties, and air will flow in the ends and out the ridge.Finish as above.
Others may suggest that you net the ceiling and blow cellulose behind the net. I'm partial to foam (closed cell ) to get max R-value in tight space. Hope this is clear to you, PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
Paul,
I'm curious why you didn't advise a third option for Justin to foam the underside of the roof up to the ridge, and do away with the ridge vent?
(great looking garage, Justin)
Sphaugh, Could have, but roofing completed, vented ridge in place, and he wants to get warm soon. Didn't think he would want to stand on that blanket of snow anytime soon.
Also, from a heat transfer point, with a ridge board, he would have a low R-value thermal bridge into his heated interior, at the hottest point of the ceiling. This could cause condensation along the underside of the ridge board. Going horizontal at the collar tie elevation, gives him full insulation depth at the ceiling max height.
By copy to Justin, suggest you visit http://www.buildingscience.com, Click "houses that work",scroll to "climate region", click "cold climate", look at wall cross section for Boston and Minneapolis. By sure to notice detail at juncture of wall to ceiling.
PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
Has anyone here purchased any of the books that Building science corp pushes? Specifically the EEBA builders guides: https://www.eeba.org/mall/builder_guides.aspjust wondering if they are a good spend. The moisture one looks interesting too.
BTW - here is the link for Building Science corp (there was a typo in the one above):http://www.buildingscience.com/default.htmMatt
Thanks, I think I am following everything. So you actually spray the foam on top of the air baffles rather than on bare roof decking? What about using foam boards on top of the collar ties to provide backing for the sprayed foam? One could glue them down with adhesive providing a pretty stable backing.
A few more questions.
In the shop, with full cathedral ceiling, would I carry the baffles all the way to the ridge and then spray everything? Would I need to box in the ridge to provide an "air box" or is running the baffles up to the ridge sufficient?
In the valley, is there a concern about the baffles being "air starved"? I saw another post suggesting drilling vent holes in the jack rafters to vent a valley.
Lastly, what about roof leaks? It would seem that you would trap the water between the plywood and the sprayed foam. It would seem that you could rot alot of decking before you were even aware there was any problem. I'm thinking of the current mold crisis related to foamboard and synthetic stucco trapping water inside walls.
Thanks again
-justin
Justin, just need a firm backing, and last piece in place will have to be tabbed to side of collar tie. You could use tyvek, if you have some left over from the wall work. The spray hits fairly forceful, not sure foam board would glue strongly enough. Have the installer be gentle, and build a layer to cure for strength before going for depth.
You only need to carry the baffles to the top of the collars, then you have an open triangle full length under the ridge vent.
In the valley, you are not providing any air due to non reachable soffit. If you look at the building science web site, you will see that you are using two different practices. 1. a vented cathedral, 2. a non vented cathedral for valley/gable.
Roof leaks are roof leaks.Your roof is not stucco with bad water plain, it is a roof. If the main vented portion of building leaks, water may run out soffit vents since you have left an air channel. However, the valley/gable can be deck sprayed, and you are relying on a good roofing job. Most cathedral ceilings are not easy to inspect.
If you are concerned, I'll tell you a little trick I have used in areas where I wanted to know what was happening inside a wall.
Had some bad copper (pin holes) behind kitchen sink wall.Framing wood got wet. After repairs, I found place where any future leak would hit sole plate. I put two screws into plate about 1" apart, and attached a wire to each.
I then put an ohm meter across the leads, and read the resistance. If the wood was dry, the resistance was almost infinity, and if still damp, the resistance fell off to almost none. Basically, I have installed a few "moisture sensors", with the wire ends just visible in cabinets, behind shower access panels, or in test walls (two finishing nails through molding and into sole plate, 1" apart, heads left bare). Just takes a second to read the "dryness" of non-visible locations. You could do the same behind the non-vented portion, but would be lucky to place where water would really leak. Easier doing a sole plate in my case. It is quite effective, and a small amount of leakage will register long before real damage is done.
What are you going to do to your walls, re insulation,and what is your heat source? Hopefully, not a kerosene burner. Paul Energy Consultant and author of Practical Energy Cost Reduction for the Home
Edited 1/13/2004 11:33:24 PM ET by Paul Hayden
"Well, we don't do that, and the 6 months out of sync are not rotting all the houses with a fixed vp"
That is not quite true.
I am in the Kansas City and would think that his is similar.
There is only about 2 months where the humity level is that high.
And I am guess about 4 months of serious heating. The remainder will be close to neutral.
I got one of the Building Science Books from the library and they look at the whole cycle.
But I agree with you that most of the moisture is carried by air movement and control that will control most of the moisture problems.
Bill, I know it is not 6 and 6. More like 4 heat for us, 2-3 neutral and the rest heavy cooling/high humidity. Re wall structure, what would you suggest? PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
Paul: what's this mean?
dedicated air to combustion burners and clothes dryers
Is that gas dryers only, or is there something to this with regard to all dryers? I've not seen an air intake on an electric dryer [but I've never looked].
Thanks.
This has been a good read.. for the last hour+
Sphaugh, By dedicated, I am refering to supplying outside air to the dryer room, and keeping the room isolated from the rest of the house air.
Regardless of ele or gas, a dryer is a house vaccum blower. It will suck thousands of cu ft of air out of the house when operating, and you have to heat/cool the replacement air. If you have an "isolated" room for the dryer, and can supply the room with air from a vented crawl space, or attic, or out side via window in the room, you can keep the dryer from exhausting conditioned air.
There are specific dimensions and placements needed in the case of a gas dryer (water heater as well) based on Btu. of total burner capacity in the "confined" space.
Another reason to provide od air, is to lessen the likely hood of creating a back draft in another combustion appliance.
Some houses have forcd air heating / A/C supply vents in the utility room. They pay to heat/cool and then exhaust that air quickly to the world if dryer running. There is a dust consideration also. With forced air systems blowing into the utility room, and a return grille elsewhere in the house, dust and lint and humidity are pulled through the house to the return. PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
A GFX is a gravity film heat exchanger. In plain English, it is a copper waste drain pipe with a copper spiral wrapped cold water line (soldered to the wall) around the drain line. When water goes down a vertical pipe, in clings to the sides, it spirals, it becomes a film and thus exposes a lot of water contact to the pipe wall. The copper pipe wall can quite efficiently transfer captured heat to the incoming cold water spiral wrapped line. I am out of town, and don't have the figures with me, but a 4' 3" dia GFX can reclaim about 50%of the heat going down a shower drain, thus warming the incoming cold water. Takes a big load off the water heater.
If you Google the subject GFX, you can get the cost/stats. Obviously, they are best used where water is flowing out as new is coming in. Payoff for the daily shower taker should be pretty fast. I believe I could make one for personal use, and will definitely install in my next house. PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
neat idea,
since i haven't gotten to much of the plumbing yet it will definately be added.. Thanks for the tip!
You are close. That 100% RH @ 30 F is 22% RH @ 70 F.
http://www.muntersmcs.com/Corp/calculator/calculator.htm
Looking at the picture inside the finished attic, could somebody explain what those green pans are that are affixed to the underside of the roof.
Thanks
PaulBen
Propa-Vents... poly foam egg crate channels to bring ventilation from the soffit area over the insulation into the free space of the attic.. then the ridge vents can complete the cycleMike Smith Rhode Island : Design / Build / Repair / Restore
Do those Propa-vents and the like have a perm rating?
I always wonder about them acting as a vapor barrier.
Look at all the big warehouse and Home Improvement stores' ceilings. They dont use foam or fiberglass. They use the foil insulation, which keeps heat in or out. They are normally made for the 24" o.c. spacing you have.
Lee,
if yiou really want to keep heat in look at how they do it with a thermos bottle,
it's foam all of the way around.. No thermal bridges to defeat the insulation, leave gaps.
Build with SIPs and you can keep a lower heating cost than any other system..