Replace old batten insulation with spray foam?

3 years ago

last modified: 3 years ago

I have an older house, built in the 50’s in hot AZ. We removed a long dropped ceiling and the batten insulation above it looked pretty rough. The contractor got a quote to replace all the insulation (even that covered by drywall) for that half of the house. He would replace the insulation with spray foam where exposed and have spray fiberglass insulation where there is still drywall in place (they would pull out the old insulation with poles and hooks and put a hose in). I have a flat foam roof. To be honest this is a huge house and the summer ac bills stay pretty low. The price to do this is 5k, which is a lot more than I was expecting. This is only for the half of the house we are working on (2000 Sq feet). The other half has mostly batten insulation which we would leave. Is it worth the expense to do this? The alternative is to replace only the exposed batten insulation with spray foam at about 2k. I’m trying to decide if the energy savings merits the expense. Thank you

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Comments (8)

3onthetree
3 years ago
IMO pulling out fiberglass batt insulation in the walls, that was cut and placed to fit, through some little hole of some sort, won't work (it'll tear) and I'd be tempted to kick that guy in the arse for suggesting that. Then blowing in fiberglass, which will not be as tight fitting down the entire wall with electrical boxes, blocking, (& leftover batts) etc as the original install was.

As far as the spray foam, you say you have a "flat foam roof." I take that as polyisocyanurate on the top side with a membrane roof. That is the best place for insulation for a flat roof and provides your moisture/air barrier. The benefit of spray foam is as a moisture/air barrier that fiberglass batts lack and more Rvalue per inch than batts. But if you already have a moisture barrier, sufficient air sealing and Rvalue, what are you looking to improve on?
scout thanked 3onthetree
scout
Original Author
3 years ago
Thank you guys! You just saved me $3000. :) The contractor was urging me to do this. My energy bills are already low for this house and it’s hard for me to imagine they would go down that much more. I don’t know if I have a membrane, but it’s a foam roof. I also have very long patio overhangs which helps to shield the interior from the sun. Thank you again!!!
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Have you thought about having an insulation company coming and blow in cellulose that has an adhesive with it? It fills up the spaces between the studs and stays there. Then you apply drywall. There are also companies that spray a foam. Batt insulation is not as good as some of these methods. Of course, you COULD use batts if you want to,but any existing foam is going to fail too.
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If you have a 6" stud cavity, its very common to not completely fill the stud cavity with spray foam. However, the closed cell foam will completely seal and insulate the wall, so it will still be very effective.. With the stud bay open they can get good adhesion on the sides so that it really seals the wall. There is some transmission of cold/heat through the studs, but its not as significant. My opinion is that keeping out cold air is more important than the depth of the insulation. You need to also ensure that your windows are installed and sealed to the wall properly as part of the project. If it was my house, I would spray the wall insulation first, and then have the electrician come in and run the wiring and install the boxes in the remaining space in the stud bay. I don't really like to have all the electrical buried in foam insulation where its not easy to access. Bruce
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David Cary
3 years ago
I might ask a local energy rater for a second opinion. When you say "low", I am always impressed by what people consider low. A better way to say it would be - I spend $2000 a year on a/c. I suspect you would think that was low (and it is for the age of house and location). But you could still potentially see a return on investment. Not a great one but still.

I personally don't have any idea how 70 year old fiberglass in AZ would look. I really doubt it would be cut well and installed with the best care.
sprink1es
3 years ago
Definitely leave alone the parts that are not damaged
badabing2
3 years ago
last modified: 3 years ago
I just blew cellulose over my batts. Blew 1000 pounds in my 1000 sq. ft attic in 4 hours. About $500. More info if interested.
fixitupchappie
3 years ago
Badabing2 I’d like to know more? What did you use to spray it?
badabing2
3 years ago
@fixitupchappie I bought a palette of this (link below) from HomeDepot - free delivery plus you get to rent the machine free for one day if you buy at least 20 bags (think it's $75/day rental, not available at all centers - check locally). Machine is a bit large but on wheels, comes with 100' of hose. Need two people - one to load the hopper, one to blow. Very dusty install - use a painter's suit and good mask (like an N95). R-Factor is 3.7 per inch (fiberglass is about R2.5/in). There's a calculator on Greenfiber site (link below) for R-value and sq. feet. Lots of good comments on the HD site and many great videos on youtube. Cellulose is (IMHO) better than fiberglass - better R-value, fiberglass is a carcinogen, recycled product, doesn't support mold, keeps critters out, etc. And you just blow it on top of whatever you have. I did mine a year ago and noticeable improvement in warmth (Central Calif), also some noise reduction too.

In short it's an easy though dusty DIY job, watch the videos, read reviews, and you'll soon be an expert.

https://www.homedepot.com/p/Greenfiber-All-Borate-Cellulose-Blow-In-Insulation-30-lbs-36-Bags-INS765LD/300584221

https://www.greenfiber.com/homeowners
fixitupchappie
3 years ago
Thanks will have to look into it

Replace old batten insulation with spray foam?

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3onthetree

scout
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Replace old batten insulation with spray foam?

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3onthetree

scoutOriginal Author

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scout
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