# Is spray foam insulation that much better than fiberglass?



## forresth (Feb 19, 2010)

the foam is good for sealing leaks and providing a vapor barrier, but its pricy. I think its faily common to do an inch or 2 and then but in the fiberglass. squirting in foam is about the only way to insulate a wall without completely opening it up. I believe I heard that there is some big lawsuite in Canada about the foam offgassing some toxic vapor. something to research before you have your house done.


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## Bob Mariani (Dec 1, 2008)

foam is a far better solution to some areas. For the garage ceiling, new work, air sealing, attics and ceilings and especially for the rim joists. For old walls use dense packed cellulose. Fiberglass is the worst choice in all applications.


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## Skuce (Nov 2, 2009)

Carpenter ants love chewing through spray foam. Ask any entomologist.

Additionally....Pink fiberglass insulation has Cancer warnings now all over it.

All blown forms of cellulose compress massively in the first 2-3 years. Almost to a point of being useless. Plus the salts that are in the stuff aren't cool for any building material if you get any humidity in the cavity.


Your best best to go is the "Roxul" insulation that is made of rock wool.


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## HautingLu (May 24, 2009)

Bob/Skuce -- is this also true for *non blow-in* applications too? Because I have access to the joists in the garage, I was thinking of using the rolls pink fiberglass.

In think what's currently in there is old rock wool, and the ceiling is covered by wood paneling. Should I just see if insulation guys will blow stuff in there without taking the paneling off? (They use something called "NuWool".

Roxul looks interesting. Looks like a lumber yard near here stocks it.


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## Bob Mariani (Dec 1, 2008)

spray foam would be too expensive for this area. Fiberglass will trap too much moisture and the blocks are not permeable enough to avoid moisture transfer. I would seal the blocks then insulate with Roxul in your case.


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## HautingLu (May 24, 2009)

Bob Mariani said:


> spray foam would be too expensive for this area. Fiberglass will trap too much moisture and the blocks are not permeable enough to avoid moisture transfer. I would *seal the blocks* then insulate with Roxul in your case.


Blocks? :confused1: Cinder blocks that is? Do you mean clean and seal from the inside with a drylock type paint, or frame and insulate?


Thanks.


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## Bob Mariani (Dec 1, 2008)

roofcoat said:


> What is the reason of foam usage? What is the difference between *foam insulation and fiberglass?
> **Nope - just a spammer - Mod*


is this a real question? the issue with fiberglass is it is damaged by moisture and made ineffective with air flow. It does not stop air flow Moisture damage in a wall cavity is caused by a leak or moisture laden air flowing into the wall cavity hitting a colder surface and condensing. Foam stops this. It is an air barrier and also has more than twice the R-Value of fiberglass.

Yes.... I mean cinder locks. Best to use a two part cementious waterproofing but dryloc will help.


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## HautingLu (May 24, 2009)

Bob Mariani said:


> is this a real question? the issue with fiberglass is it is damaged by moisture and made ineffective with air flow. It does not stop air flow Moisture damage in a wall cavity is caused by a leak or moisture laden air flowing into the wall cavity hitting a colder surface and condensing. Foam stops this. It is an air barrier and also has more than twice the R-Value of fiberglass.
> 
> Yes.... I mean cinder locks. Best to use a two part cementious waterproofing but dryloc will help.


Thanks Bob. Looks like I have my next summer project.

Any recommendations on a two part waterproofing product?


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## Bob Mariani (Dec 1, 2008)

try thoroseal with an additive. Others are more for commercial use.


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## HautingLu (May 24, 2009)

Bob Mariani said:


> try thoroseal with an additive. Others are more for commercial use.


Thanks again. 

I also have some plans for the outside: remove sinking sidewalks, french drains, and re-grading.

p.s. can storm drains (for downspouts) be added in the same ditch as french drains, or is that just being redundant?


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## Bob Mariani (Dec 1, 2008)

They can. Not redundant and should not be interconnected. In the ditch you will use solid pipe for the downspouts and perforated pipe (holes down) for the drainage system.


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## federer (Aug 20, 2010)

so is putting in spray foam in the attic ok with the roof system?


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## HitLines (Aug 31, 2009)

http://www.diychatroom.com/members/hautinglu-54326/HautingLu, are you looking to do the spray foam yourself?

If so, where are you picking it up? Online or a local supply? I am also planning on using spray foam above the garage to help keep a master bedroom warm. Filling the entire bay of 2x8 (might be 2x6) would be expensive but I think a 2" layer of foam with rolled insulation then drywall would be sufficient.


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## steveel (Sep 10, 2010)

If the unheated attic is above an unheated garage, why are you thinking about insulating the unheated attic's roof? Unless I missed something, sounds like the "thermal envelope" does not include the garage, so you're looking at insulating the wall between the garage and the house and the attic floor above the house. 

*I would do all the exterior drainage work first. *If they trash part when they later install geothermal, too bad. Bulk water runoff is much nastier against the house than a wall with no insulation so cure that first.

After that, I would air seal the thermal envelope. If you go with spray foam for the insulation then air sealing and insulating is a one step process. If you choose some other material for insulation then air sealing is step 1 and insulating is step 2. Rock wool will not air seal. Wood, spray foam, caulk will air seal, but not any of the loose insulations. If you are worried about ants, then control the standing water and clean up dead wood, and maybe treat the perimeter for ants. I'm mystified why the earlier commenter thinks fiberglass, properly installed in a building that properly control inside and outside moisture will "trap moisture". That's a new one on me, but then I am learning all the time. Maybe they'll explain.

You might want to consider insulating the basement walls and floor and turn that into living space. Cheaper than adding on.

Whatever you do, the Winter 2010 edition of Taunton's Energy Smart Homes had several articles that apply to your questions. I think they have a new edition out but I have not seen it.

Good luck
SteveEl


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## SPS-1 (Oct 21, 2008)

... but all spray foams are not created equal. There are open cell spray foams, closed cell, low density, high density, water based, polyurethane,........... etc I have not priced spray foam, but I expect, like most things, the cheap stuff is not so good

Bob, when you suggest sprayfoam for the garage ceiling, I expect you are suggesting something like a high density, closed cell polyurethane. Is that right ?


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## steveel (Sep 10, 2010)

Dope. I misread. I see now you DO have living space above garage.

If it were my garage, based on what I know, I'd look behind the panels. If it's insulated in there then what's the problem with that space? It might lack air sealing between the joists, where the joist bay meet the exterior walls but that would be easily fixed with blocks of that pink foam board glued in place between the joists with that GreatStuff blowfoam. It its not insulated between the joists, then I'd still use that pink foam board between the joists where the joist bays meet the exterior wall, glued in place with some GreatStuff blowfoam, and then I'd put up UNFACED batts of the insulation of your choice provided its approvied by your inspector for fire issues related to attached garages. I see no reason to blow foam in the garage. I assume you're not running your car in there in the winter to warm up right? You have the depth of the floor joists for new insulation, and its not exposed to much wind pressure so why not just use batts? More important to air seal the ends of the joist bays around the exterior walls, and then the walls and ceiling of the living space. Main reason I see to spray foam between the joists is to keep cold air from getting up into the living space from below, but iIf hot air doesn't go UP thru the ceiling/walls of the living space it won't be sucking cold air in from the garage so why not fix that problem from above? 

==========================

Also, does that duct need attention?

==========================

Review your plan with your building inspector with attention to fire spreadhing issues due to attached garage. 
SteveEl


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## concretemasonry (Oct 10, 2006)

Use a litttle spray foam to seal cracks and corners and then blow cellulose into the ceiling a few inches above the top of the joists (or more since it will not raise the cost much) with cellulose and you will minimize the thermal short-circuiting of the wood joists that reduce the real R-values below what the pink panther says. It is far superior to fiberglass and does not hold moisture that can cut the insulating value in half.

Dick


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## steveel (Sep 10, 2010)

The living space's floor would be in the way, and properly installed cellulose stays wet much longer than properly installed fiberglass of the same R value (of course if they are properly installed, for them to get wet in the first place would require something unexpected).


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