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-   -   Is spray foam insulation that much better than fiberglass? (http://www.diychatroom.com/f2/spray-foam-insulation-much-better-than-fiberglass-67432/)

HautingLu 03-23-2010 12:21 PM

Is spray foam insulation that much better than fiberglass?
 
I have an uninsulated living area above a cold garage. Additionally, the rest of the house is over an uninsulated cold basement. I want to put in geothermal this Fall, and the contractor recommended that I seal up the house so they don't oversize the system.

I want to insulate the garage ceiling and the rest of the basement, but I'm trying to figure if the new spray foam is that much better? Originally I was leaning towards the traditional method (vapor barrier, fiberglass, drywall), but I've been seeing that foam has a higher R value.

My problem is that I will be probably be redoing plumbing and wiring in the basement, so I will need access to under the floor. I'm guessing foam isn't the best choice here? But if I don't need access in the garage, is foam the better option?

Besides that, I will probably have most of the windows replaced and I'm also considering whole-house insulation. How messy is foam in retro fits if plaster or drywall needs to come out in the future (i.e. remove plaster and install drywall)?

Thanks.


p.s. in the case of a cold garage, does the vapor barrier go against the floor, followed by insulation since that's the "winter-warm" side?

forresth 03-23-2010 06:48 PM

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.

Bob Mariani 03-24-2010 07:41 AM

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.

Skuce 03-24-2010 12:14 PM

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.

HautingLu 03-24-2010 04:16 PM

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.

http://imgur.com/1cLLz.jpg

Bob Mariani 03-24-2010 08:24 PM

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.

HautingLu 03-24-2010 10:34 PM

Quote:

Originally Posted by Bob Mariani (Post 419183)
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.

Bob Mariani 03-25-2010 07:45 AM

Quote:

Originally Posted by roofcoat (Post 419329)
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.

HautingLu 03-25-2010 08:34 AM

Quote:

Originally Posted by Bob Mariani (Post 419350)
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?

Bob Mariani 03-25-2010 10:52 AM

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

HautingLu 03-25-2010 11:32 AM

Quote:

Originally Posted by Bob Mariani (Post 419411)
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?

Bob Mariani 03-25-2010 02:59 PM

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.

federer 09-21-2010 01:40 PM

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

HitLines 09-21-2010 02:16 PM

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.

steveel 09-21-2010 04:25 PM

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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