Foil Backed Commercial Insulation

Glenn F. · Apr 9, 2015

Do any of you know the r-value of commercial foil backed 1.5" fiberglass insulation? This is the type commonly used on large commercial buildings (or at least used to be). Does the thick foil raise the r-value at all?

Thanks
Glenn F.

JF in MI · Apr 9, 2015

I've never seen the 1.5" stuff but I did some basement insulating projects with the 1" stuff and that is R-6.5. I really like it and plan to do another project with it in my outside work room.

Russ from MN · Apr 9, 2015

That's an awful big number for fiberglass! I would believe it if it was hi-dense foam.

Jason the Red · Apr 9, 2015

Been a few years, but if I recall correctly it is r-9. I'm thinking it is used in 1 5/8 metal studs.

JF in MI · Apr 10, 2015

Oops, I read the post wrong. I thought it was hi-dense foam he was talking about. You are correct.

Geo-TH,In · Apr 11, 2015

Glenn,
The R value of anything is 1/U. U is the conductance of a material. Normally 3.5 inches of fiberglass can have an R value ranging from 11 to 15 depending on it's density. R 15 is high density, special order and expensive. So 1.5 inches of fiberglass could be anywhere from 5.5 to 7.5 depending on density. I have many insulation wholesale supply places. That would be a good source to find out what your R value is. I'm going to say, 1.5 inches of fiberglass is has about the same value of ¾ of extruded urethane. Urethane for fire safety reasons needs covered fiberglass doesn't.

Aluminum stops radiant heat transfer which is different from conductance. There is no formula that I'm aware of for radiant heat transfer. However, IMHO, radiant transfer is very important.

When I build on an addition or remold, I like to put up 3/4 inch extruded urethane, which is coated on both side with aluminum. The urethane is cover with drywall. The 3/4 inch has an R of about 5, but the aluminum makes a great difference in stopping radiant heat loss and gain.

Foil Backed Commercial Insulation

Glenn F.

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JF in MI

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Russ from MN

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Jason the Red

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JF in MI

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Geo-TH,In

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