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Message
Foam vs Cellulose insullation
Posted on 4/29/21 at 1:35 pm
Posted on 4/29/21 at 1:35 pm
I always liked cellulose over foam but most of the builders I talk to are all about the foam.
I’ve heard some stories about termites which keep me away.
Any real world thoughts on it?
I’ve heard some stories about termites which keep me away.
Any real world thoughts on it?
3
Posted on 4/29/21 at 1:58 pm to SlidellCajun
Yes! Foam is fantastic for damp, wet areas like rim joists, basement walls, crawl spaces, etc.
I'm a big advocate of "dense packed" blown cellulose over spray foam for above grade walls and attics. My main reasons are:
1) Cellulose provides much better sound attenuation than either type of spray foam. I have been in some foam houses and they are not well isolated from outside noise.
2) cellulose decreases infiltration rates as far as you can reasonably go without adding HRV/ERVs. When you go foam in the walls/attic the house becomes too tight and you have "force" so many air changes per hour. This means you have to bring in outside air and send your conditioned air back out. It is another piece of HVAC equipment that needs controlled, maintained and repaired.
3) Closed cell foam is too rigid. It can separate from the substrate over time. So that nice super tight aspect of closed cell foam can be undone when the closed cell foam pulls away from the studs/sheathing allowing more outside air to come right in. This may not be a big issue down south but further north where houses are prone to lots of freeze/thaw cycling it can be problematic.
4) Spray foam in the attic is just inconvenient. You have to cut it out to do any work up there. Makes replacing exhaust fans or repairing duct work more difficult.
5) I prefer to have my ductwork in the attic covered by the insulation. When you foam in an attic the duct work just lays on top of the foam. Yes, ductwork is insulated but that is usually only R-8. I like having the additional cellulose or blown fiberglass covering the ductwork completely to help improve performance.
6) Up here further north the R-Value of cellulose drastically increases as outdoor temperatures drop.
I did use spray foam to do my rim joists and cover the concrete walls of my basement when I finished it. I don't think you can find a better insulation for those applications than spray foam.
I'm a big advocate of "dense packed" blown cellulose over spray foam for above grade walls and attics. My main reasons are:
1) Cellulose provides much better sound attenuation than either type of spray foam. I have been in some foam houses and they are not well isolated from outside noise.
2) cellulose decreases infiltration rates as far as you can reasonably go without adding HRV/ERVs. When you go foam in the walls/attic the house becomes too tight and you have "force" so many air changes per hour. This means you have to bring in outside air and send your conditioned air back out. It is another piece of HVAC equipment that needs controlled, maintained and repaired.
3) Closed cell foam is too rigid. It can separate from the substrate over time. So that nice super tight aspect of closed cell foam can be undone when the closed cell foam pulls away from the studs/sheathing allowing more outside air to come right in. This may not be a big issue down south but further north where houses are prone to lots of freeze/thaw cycling it can be problematic.
4) Spray foam in the attic is just inconvenient. You have to cut it out to do any work up there. Makes replacing exhaust fans or repairing duct work more difficult.
5) I prefer to have my ductwork in the attic covered by the insulation. When you foam in an attic the duct work just lays on top of the foam. Yes, ductwork is insulated but that is usually only R-8. I like having the additional cellulose or blown fiberglass covering the ductwork completely to help improve performance.
6) Up here further north the R-Value of cellulose drastically increases as outdoor temperatures drop.
I did use spray foam to do my rim joists and cover the concrete walls of my basement when I finished it. I don't think you can find a better insulation for those applications than spray foam.
This post was edited on 4/29/21 at 2:09 pm
Posted on 4/29/21 at 2:11 pm to SlidellCajun
Foam
Posted on 4/29/21 at 2:52 pm to SlidellCajun
Why cellulose instead of spray fiberglass which goes on dry? I've been in new construction houses, prior to drywall being installed. Seems cellulose packs really bad leaving a void.
Posted on 4/29/21 at 3:16 pm to HeartAttackTiger
Dense packed cellulose installations is probably what he was referring to.
Posted on 4/29/21 at 3:19 pm to HeartAttackTiger
quote:
Why cellulose instead of spray fiberglass which goes on dry? I've been in new construction houses, prior to drywall being installed. Seems cellulose packs really bad leaving a void.
Blown cellulose is dry. Just like blown fiberglass BIBS, cellulose must be blown/packed to a density higher than the natural settling density to prevent, well, settling. When it is dense packed you get no voids short term or long term.
Blown fiberglass has the same issues and requires dense packing.
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