Insulation for Adirondack weather
Can you weigh in on this debate on where to place foam insulation?
I’m building a house in the Adirondacks, where the temperatures can reach 100 degrees in summer and minus 20 in winter. average temp in winter is probably 20.
The master bedroom / master bath is on the second floor and it is the only room on that floor (sitting like a box on top of the first floor). it is approx 760 sq ft. with a flat 8′ high ceiling (trusses used with a 10-12 roof).
One insultaion contractor recommended foaming the roof rafters and doing nothing else (i.e. foam or standard insulation on the ceiling). Another recommended foaming the ceiling leaving the roof rafters ‘untreated’. A third foam contractor said he doesn’t make the recommendation of wher to foam … leaving the decision up to the homeowner. Which makes me wonder if there is still controversy regarding foam and where to place it … and whether or not the product is ‘old’ enough to have a proven record on where to place it.
Any comments are greatly appreciated!!
thanks
Tom
Replies
I gotta ask.
What did your builder recommend?
And where are you in the Adirondacks that it only goes to twenty below?
And who is designing your heating installation? They might have some input about your insulation.
Without some more facts, what can we possibly advise?
BTW, I'm in the 'dacks, also.
Thanks Gene. I'm in Keene.
Hyde is getting a heat loss plan togeter for me for the heating system. I'll ask them their opinion as well.
My builder was the one who called these three contractors and he was surprised with the three different responses; and wondered why one 'left the decision to the homeowner' ... wondered if it was because these new foam materials (and placement of) were still too new and without a long term record, such that some contractors didn't want to make a specific recommendation.
My builder used foam in the roof rafters in a bedroom over a garage that he built for himself. he added collar ties (not sure of distance from ridgeline) and plans to sheetrock these ties without any additional insulation.
Tom
Is there going to be any HVAC in that attic space?
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
A lot of people will argue for insulating the ceiling. Less space to heat obviously. There also those who believe a cold roof is another benefit for insulating the bottom of the trusses. It will be less expensive since there is less square footage to insulate and you also have the option of going with fiberglass which will save you even more $ and there are those who will steer you in that direction.
If given the choice of urethane or fiberglass I always choose foam for walls and ceilings. Also as far as dependability I've pulled out more junky old fiberglass than I'd like to remember, like I said junk. Remodeling a house insulated with foamed is like tearing apart an igloo cooler! It's a totally different structure.
Personally I've had much better performance from spraying foam at the rafters even in trussed areas like your situation. The only ice damn issue that I've encountered was on a house that had a trussed master wing and we chose to insulate the ceiling, per the architect's plans, but went a step further and used Icynene instead of fiberglass. There were a lot of contributing factors that caused the ice damn but personally I feel we could have avoided it by spraying the roof instead. I have since built a home designed by the same architect with the same specs and a very similar roof line but this time we opted to spray the roof and cover the top chords completely with foam. No problems so far. I should add that this is all in the mountains of Montana where we see our fair share of weather extremes also :)
Well there's my spheel just my experience with it.
"Less space to heat obviously. There also those who believe a cold roof is another benefit for insulating the bottom of the trusses. It will be less expensive since there is less square footage to insulate and you also have the option of going with fiberglass which will save you even more $ and there are those who will steer you in that direction."Less space to heat and fewer sq ft to apply is a factor, but a fairly minor one.The vol;umn heated has little to do with cost of heating. It is primarily the sq ft of surface area through which heat energy might leak that is important to consider. Admittedly, with a steep roof like this, there is some extra sq ft to factor n.But the main point of yours that I would argue against is that of substituting FG there. That is the absolute worst choice for an effective insulation of all that is available in this country. Beyond that, one of the great advantages of the foam is that it acts as an air barrier. A great soure of heaat loss in most houses is infiltration. When you take aay the foam at the top - the most critical place, you allow convection loss there whih creats a negative pressure in the house, sucking cold air in everyplace it can find to come down at sills and windows, doors, etc. Changing the air in the house every hour or less means heating all new air that ofen, which is expensive.
OTOH, keeping the air by controling infiltration means keeping the heat.
Which can then lead to need for a heat recovery ventilation system with the HVAC, another reason he needs an overall plan to tie it all together. Haphazardly substituting one elenent for another throws everything off
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Just laying out the options. I like to give people as much info as I can so they are responsible for their decisions. Did you only read the 1st part of my post? I was stating the other side first which is not the side I'm on. I absolutely loath fiberglass but was trying to be nice about it.
I went on to say that I chose foam every time if given the choice. I have built 2 homes in my career with fiberglass and it was not my choice. I think it is junk as I stated in my 1st post.
Foam, foam, foam. Use it! Also I put a air exchanger/HRU in every home I build. IMO all this should be planned out from the get go while plans are being generated. Good insulation costs a bit more but will save you $ over time.
We are agreed. Didn't mean to step on your toes.
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Piffin:
On the same topic, how about my 200 year old house in Maine (actually, the roof in question is only about 100 years old, because someone ripped off the original hip roof and replaced with a gable, about 8/12 pitch)? It costs a bundle to heat. Windows are pretty tight and the walls got blown in cellulose years ago, but when I open a wall, the insulation seems pretty tight.
The attic floor is insulated with fiberglass batts that were there when I bought the house. For the most part, the attic floor joists are covered with plywood, but I can see that a lot of the insulation is not doing much-lots of gaps, squashed batts, dirt, missing batts, etc.
Here is the question. Would it make sense to leave the fiberglass and foam the rafter spaces, rather than clean all the #### out of the attic, remove the plywood, remove the fiberglass and replace it with something better? There are small gable end vents and windows at each end of the attic, no soffit vents or roof vents. The attic is accesable via drop down stairway and hoses could come through the windows. I haven't measured it (I'm not home at the moment) but the floor area is about 40 x 20.
If foam makes sense, what kind of foam and how much? This will not be a do it yourself project, if I can help it.
Thanks.
If you need the floor space for storage and misc. then that might be the way to go, but you'd have to insulate the gable end walls and do away with vents and assess the rest of your vapour control there.But if you can give up floor space there, just lofting a lot more blown in cellulose or chopped FG would be a far more economical way of adding insulation. I am all for foam, but it is not the most practical in every case.
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I do need the space, but I could take up the plywood, which is only nailed down enough to hold it in place. I could then remove or clean up the crappy insulation and add more. Of course, that makes a do it yourself project, which I'm trying to avoid, but perhaps it will require a new bandsaw or other necessary tool:-).
Thanks for the advice.
Happy Buildmore & Piffin,
Thanks for your advice and insight. sorry it took me a while to respond. I will be doing my homework and appreciate you guys pointing what to study. I may be back with more questions later.
Thanks again!
Tom Pendlebury
There are a LOT of diffeent factors that your architect and builder SHOULD be aware of in order to make this decision but it appears that they are not on the ball here.
It will vary relative to the overall plan that combines insulation, ventilation, heating, and moisture control. All systems have to work together and the insulation ontractor should not be the primary focus nor have the control to decide this.
First, you mention three different contractors to install foam.
What kind of foam? That is highly pertinent!
Open celled foams have less than R-4 resistance to heat loss and they serve as a vapour retarder/air barrier, but not as a vapour barrier. So they would be better to install thicker and on the ceiling level with attic ventilation above. some open celled foam has been known to soak up water out of the air and hold it for mold production....
Closed cell foams are rated R-7/inch and are generally vapour barriers also. They are fine to place right up at the rafter/sheathing level. They can go on the ceiling just as well too, depending in part on where you want your VB placed.
If you are placing the HVAC unit in the attic, it has advantages to being in a conditioned space, so again spraying at the rafters is better for that consideration .
Some installers might have a preferrence for one way or the other based on how easy it is for them to do the job with no concern for what is best for you.
there is concern ( unwarranted for the most part, IMO) that spraying the rafter level and making a hot roof will decrease shingle life for omposition type shingles.
A builder and designer should have an overall philosophy for how to marry all this together. that is the skeleton on which you hang all the details so they can work together.
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