question about insulation choices

17 years ago

We have an old home, but this forum seemed the best choice for this question; I hope that's ok.

We have been getting estimates for insulation and have settled on 2 companies with different types. I've done some reading here, but everything seems so relative to different factors I was hoping to get some input specific to our situation.

Our situation: We are using a local energy rebate to insulate our attic over the whole house and the crawlspace under the addition. The attic space is triangular front to back and not high enough to even crouch in, crawl only. We have a barn type roof where the bottom part forms the outside walls of the 2nd story. It has a small amt of old fiberglass batt insulation, R8, we are in Chicago. We have to replace the roof this summer, and the rebate ends at the end of this month. All roofing quotes we've gotten have included a ridge vent. The crawlspace is not sealed and there is insulation on the walls only (VERY cold kitchen floor this past winter!)

Quote 1: Owens Corning Propink blown-in fiberglass, 12' of R30 to bring it to R38 to be eligible for the rebate. 6' batt to border the access opening. Crawlspace: insulate the ceiling with R30 batts.

Quote 2: Icynene insulation. 5.5' Of 1/2 Pound Open Cell Spray Foam Insulation to the attic floor and crawlspace ceiling and 3.5' to crawlspace walls. We would remove the current fiberglass insulation ourselves to save $

There is a $400 price difference. Thank you for any opinions and/or advice!

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Comments (3)

vhehn
17 years ago
for 400 diff i would go with the foam.
worthy
17 years ago
There is no point in insulating the crawl space walls and then leaving the space vented so it's essentially outside anyway.

Instead, seal the crawlspace and treat it as conditioned space. Among other benefits, that will save you the money you'd spend on uselessly insulating the crawl space ceiling. (Let alone, if you were leaving it a vented space, the insulation on the crawlspace ceiling is by itself absolutely useless as a thermal barrier.)

See Building Science Corp. research reports -0401 and -0509d at the link below.

Here is a link that might be useful: Building Science Corp.
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blackcats13
Original Author
17 years ago
"There is no point in insulating the crawl space walls and then leaving the space vented so it's essentially outside anyway."

The foam insulation guy was very clear on this very same point, and on how well foam would seal it all up. Even the fiberglass guy and the energy auditor couldn't understand the way it was done (it's not intended to be vented space). I was actually looking at that link before I had to go do some cleaning (found it in another of your posts). Thanks so much!

Vhehn, I was thinking the same thing. I was just a little unsure about the open cell in this application. And, of course, I'd rather spend my time doing other things then removing old insulation myself ;)