Exterior Insulation around Foundation

sands35 · May 23, 2013

Reading through the guidelines on frost protection. (garage has 42" footers, looking at it more from an energy savings, then from the frost protection needs).

http://www.toolbase.org/PDF/DesignGuides/revisedFPSFguide.pdf

What is common for a DIY job to protect the insulation board above and below grade?

Cement board looks like the simplest with an AL flashing cap. What about some of the spray/roll on stuccos?

Any experience with this?

blkhonda1991 · May 23, 2013

sytro industries makes a few coatings for above grade, no reason to worry about it below grade.

burleyfarm · May 24, 2013

I'm doing the same thing this fall. One inch foam with brush on cement coating. Flashing/drip edge between the vinyl siding and foam. I want to reduce the amount of heat transfer from my heated garage to the outside in the winter. My foundation is only three blocks high, sitting on a concrete footing. I'll have on average 6-8 inches exposed. I'm going down the 24 inches to the top of the footing but have to wait till fall after the flowers in the bed next to the garage have died back.

Wish I would have done this before pouring the concrete drive as I won't be able to insulate 36 feet along the front of the garage.

Has anyone else done this?

NUTTSGT · May 24, 2013

blkhonda1991 said:
sytro industries makes a few coatings for above grade, no reason to worry about it below grade.

I disagree about not worrying about below grade. If you plan on heating continually the garage, you want the concrete floor to act as a heat sink and absorb the heat. By insulating the foundation and below grade, you create a thermal break to keep the cold away.

fpianka · May 24, 2013

By "no reason to worry about it below grade," I wonder if he meant the protection of the insulation with the brush-on cement, and not the complete omission of insulation below grade. Related question: what insulation/vapour barrier/geotextile materials should go below the slab and in what relative position? Would insulating under the slab reduce the thermal mass available to retain heat, provided the perimeter is insulated properly?

1233user · May 25, 2013

I had a local sheet metal shop bend up some stainless steel sheet metal to protect the styrofoam insulation that was above grade on my garage addition. I thought about what to do with this for awhile, and decided that the stainless was the only thing that would offer strong enough protection and I would never have to worry about it again. It was a little expensive, but it was really easy to install, and won't require any maintenance in the future.

NUTTSGT · May 25, 2013

1233, what does that look like now that it's done ?

1233user · May 25, 2013

NUTTSGT said:
1233, what does that look like now that it's done ?

Well, the garage isn't built yet, just the foundation and backfill done. I don't have any pictures with it backfilled, but I can take some. I think it looks great. The stainless weathered a little bit over the winter, so its not as reflective as it was when new. Unless you look at it closely, you don't even know that your not looking at the concrete. I'm very happy with how it came out.

burleyfarm · May 29, 2013

fpianka said:
By "no reason to worry about it below grade," I wonder if he meant the protection of the insulation with the brush-on cement, and not the complete omission of insulation below grade. Related question: what insulation/vapour barrier/geotextile materials should go below the slab and in what relative position? Would insulating under the slab reduce the thermal mass available to retain heat, provided the perimeter is insulated properly?

I'm pretty sure that's what he meant.

theoldwizard1 · May 29, 2013

2" of foam minimum, 4" is better especially if you have radiant heat. It should go down to the frost line. Above ground needs protection.

srode · May 29, 2013

That's a great patch for termites to follow and have a good feed undetected.

ed_h · May 29, 2013

I've used the Styrofoam brush-on stuff. It looks good and lasts if you can protect it. It is a little fragile.

jkeyser14 · May 30, 2013

srode said:
That's a great patch for termites to follow and have a good feed undetected.

Agreed. I see the benefits of below grade insulation, but I would be afraid that it would destroyed by ants and termites in just a couple years.

ed_h · May 30, 2013

jkeyser14 said:
Agreed. I see the benefits of below grade insulation, but I would be afraid that it would destroyed by ants and termites in just a couple years.

I've seen field mice hollow out a little pocket and nest in the rigid insulation, but never saw evidence of insect attack. I think the implication was that termites would travel undetected under the insulation to get to wood.

jkeyser14 · May 30, 2013

ed_h said:
I've seen field mice hollow out a little pocket and nest in the rigid insulation, but never saw evidence of insect attack. I think the implication was that termites would travel undetected under the insulation to get to wood.

Carpenter ants love the foam because it's the same consistency as rotted wood. Termites love it because it gives them a protected, easy to bore through path to various parts of your home.

http://www.ornl.gov/sci/buildings/2012/Session PDFs/153_New.pdf

Here's a good technical paper that details the need for specially treated foams. They have mostly done short term tests on the foams, with some promising long term results, but if you look at how they define "long term" it's "3 years or greater". I don't care if the foam is good for 3 years, I want to know if it will be good for the life of the structure.

Exterior Insulation around Foundation

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