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grover
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# Posted: 10 Oct 2014 02:55pm
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I'm to the point where I need to make a decision on what insulation to use. I have quotes from 2 companies.
The first is a combo of foam and cellulose. Wet blown cellulose on walls and closed cell foam on ceiling quote is about $3800. If I go closed cell on walls and ceiling (no cellulose) it is about $6000. Ouch!
The second is open cell in walls and on ceiling. About $4000
I started to look at doing cellulose myself in walls (netting) and ceiling and I came up with about $900. That is a huge savings up front. For a place that may never be a full time residence it seem tough to justify a $3000 dollar difference.
Opinions anyone?
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bldginsp
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# Posted: 10 Oct 2014 06:48pm
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I'd only use closed cel spray foam if I had to. That would be if it were a ceiling design that could not be ventilated. Otherwise, I'd use something else and ventilate above the insulation.
Did you price buying rigid foam insulation and cutting/fitting it yourself?
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grover
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# Posted: 11 Oct 2014 07:38am
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Why do you say you would only use it if you had to?
The roof system is made up of scissor trusses with small attic space with very limited access when finished. It is just a rectangle with a simple straight roof line. From the lower part at the wall to the ridge is about 16 ft so I think the best way would be to staple in the vent chutes to maintain a channel for air flow. Then staple in some Kraft faced R13 or R19 in the bottom 10 ft or so then blow that portion in. Then I would have to work it in sections from one end to the other, stapling and blowing in as I go. The other issue to deal with is the cellulose will probably want to tumble down the incline.
In theory it sounds like a real pain in the butt so I'm sure in practice it would be even worse.
The foam is sounding better now.
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bldginsp
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# Posted: 11 Oct 2014 11:08am
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Perhaps from an installation standpoint the foam is a lot easier in your case. I would only use it if I had to primarily because of the cost. But also the closed cel is supposed to 'seal' out moisture, eliminating the need to ventilate, and eliminating the ability to ventilate. I prefer a ventilated situation. I just can't imagine building a roof that doesn't ventilate. Something in my gut says it has to be problem, somehow, somewhere. But that's just me and my paranoid delusions of moisture condensation. I've seen enough moldy insulation to want to avoid that at all costs.
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creeky
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# Posted: 11 Oct 2014 03:04pm
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I would see if Razmichael posts on this. You might search his posts. He did a closed cell attic insulation. r38! It seems to work for him. you might also go to buildingscience dot com etc to see what they say.
the advantage to closed cell, is, as you know, moisture resistance and higher r value. short term pain ($$) for long term gain. you do need a ventilation path for the roof sheathing to the exterior... but...
cellulose walls have a reputation as high quality insulation with the downside of - it is very hard to find good installers. if you have a good installer you're in great shape. if they haven't done it, maybe go to buildingscience dot com and look up "perfect wall."
i personally have done the rigid foam board cut and fill gaps with expanding foam/roxul insulation many times (well. 3) and it works the ticket. very cost effective also. great diy solution. You lay the roxul between the joists and then put sheets of (i use) polyiso over (that's also your vapour barrier) and then add your ceiling treatment. gypsum or ...
sounds like you have a bit more budget. my chips would fall with option a. closed cell roof/cellulose wall. nice.
note: I'm only an experimental enjoyer of small building construction.
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DwellerofCabin
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# Posted: 11 Oct 2014 03:44pm - Edited by: DwellerofCabin
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Met a neighbor who lives in a very large dry cabin. About 900 sq ft. She used tightly crumpled news paper then covered with plastic in the interior. She has no fungus problems and it keeps her place very warm. I was concerned with flash point and found newspaper was nothing more than cellulose, only not processed with chemicals. Flash point is 450 deg. F! Where as other things like spray foam is at 250-275 depending on mfg. I have used it with caulking every seam there is then laying tin foil on the wall with a few staples for deflection on the suns heat then stapling up 4 mil plastic for a vapor barrier half way up and fill in the voids with heavily crumpled newspaper. (I am developing some awesome biceps doing this). Can't believe how toasty my little 12x20 cabin is. Like I said, the flash point on newspaper is so much higher than I thought and oh so cheap!!! By the way, the woman was 78 and up on her roof replacing her shingles on her second story when I met her. She was happy to hear there was another cabin dweller moving in the area. I also am a woman, 64 and loving the way I live!
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