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Stephen Carroll Posted: Jul 23, 2015 12:16 PM	Spray foam over garage as well as house? Hello - We're about to buy a 2800sf (heated & cooled) 1-story home, built in 2005, currently with blown-insulation. Plan to be in the home forever. So we're looking at spray foam. The house has a 3-car garage, attic is currently one space continuous through the building. Insulation Company A suggests spraying all the roof area with 5.5" open cell, and also make & spray walls (made of plastic stapled to the trusses) to separate the conditioned space from the space over the garage. Company B suggests forget the walls, spray the entire roof area including over the garage. (Being in Florida I liked the idea of a cooler garage.) Company C suggests that if we want to spray the roof area over the garage, we'd also need to spray the garage ceiling (i.e. the attic floor over the garage), so that the garage attic area becomes part of the conditioned attic area over the rest of the house. All 3 companies seem to have good logical reasons for their plan. Any help / advice on these scenarios would be much appreciated! Steve in Florida.
mason Posted: Jul 28, 2015 01:27 PM	I replied to this earlier but don't see it posted. A: I agree with separating the garage attic section from the house attic section, but I don't agree with using plastic stapled to the trusses. It does not make a structural wall assembly that would pass building codes. Had a lawsuit that I worked on in West Texas and this was one of the items that was being fought over. B: Spray entire underside of the roof deck including the garage. Garages contain a lot of stuff that can add to poor indoor air quality such as paint, thinner, gasoline, carbon monoxide fumes from cars, etc. With an unvented attic assembly, the fumes would stick around and can drift into the house. So I don't like this specific option Unless: C. You spray the floor of the garage attic to prevent fumes from entering the house and then spray the underside of the roof deck. Your most energy efficient and safe option would be to build a real wall (studs and drywall) separating the garage attic and the house attic, spray with foam and then spray the underside of the roof deck on the house attic side. Next best would be option B
mason Posted: Jul 28, 2015 01:28 PM	I mean next best option would be C not B

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Stephen Carroll

Posted: Jul 23, 2015 12:16 PM

Spray foam over garage as well as house?

Hello - We're about to buy a 2800sf (heated & cooled) 1-story home, built in 2005, currently with blown-insulation.
Plan to be in the home forever.
So we're looking at spray foam.
The house has a 3-car garage, attic is currently one space continuous through the building.
Insulation Company A suggests spraying all the roof area with 5.5" open cell, and also make & spray walls (made of plastic stapled to the trusses) to separate the conditioned space from the space over the garage.
Company B suggests forget the walls, spray the entire roof area including over the garage. (Being in Florida I liked the idea of a cooler garage.)
Company C suggests that if we want to spray the roof area over the garage, we'd also need to spray the garage ceiling (i.e. the attic floor over the garage), so that the garage attic area becomes part of the conditioned attic area over the rest of the house.

All 3 companies seem to have good logical reasons for their plan.
Any help / advice on these scenarios would be much appreciated!
Steve in Florida.

mason

Posted: Jul 28, 2015 01:27 PM

I replied to this earlier but don't see it posted.

A: I agree with separating the garage attic section from the house attic section, but I don't agree with using plastic stapled to the trusses. It does not make a structural wall assembly that would pass building codes. Had a lawsuit that I worked on in West Texas and this was one of the items that was being fought over.

B: Spray entire underside of the roof deck including the garage. Garages contain a lot of stuff that can add to poor indoor air quality such as paint, thinner, gasoline, carbon monoxide fumes from cars, etc. With an unvented attic assembly, the fumes would stick around and can drift into the house. So I don't like this specific option Unless:

C. You spray the floor of the garage attic to prevent fumes from entering the house and then spray the underside of the roof deck.

Your most energy efficient and safe option would be to build a real wall (studs and drywall) separating the garage attic and the house attic, spray with foam and then spray the underside of the roof deck on the house attic side.

Next best would be option B

mason

Posted: Jul 28, 2015 01:28 PM

I mean next best option would be C not B

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