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Any way to abate thermal consequences due to required 2" termite inspection gap?

Hi All,

We are using Foamglas for insulating under our slab as well as the slab edges (monolithic slab on grade). It is a requirement to leave a 2" gap above the Foamglas on the slab edges for termite inspections. Are there any options to satisfy this requirement, but not have the thermal gap? Perhaps industrial strength velcro or something :) ?

Thank you,
Stacey Owens

Asked by Stacey Owens
Posted Jul 18, 2014 4:00 PM ET

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6 Answers

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I would hope that you can convince "the powers that be" that a termite inspection gap is not needed with Foamglass. Foamglass is completely immune to attack by wood boring insects, from what I've read it is equivalent to concrete in this respect. The gap requirement is there for the plastic foams which are subject to attack but Foamglass is VERY different.. Since it's the slab edge and not subject to compressive stress you might see if mineral wool board stock, such as Roxul Drainboard would be approved without the inspection gap, even though it is actually slightly inferior in resisting termite attack it doesn't have foam in it's name.

Answered by Jerry Liebler
Posted Jul 19, 2014 3:15 PM ET

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Jerry,
The reason that people who live in termite-infested areas want to have an inspection strip isn't to protect their insulation. It's to protect the wooden components of their house.

You want an inspection strip so that it is easy to see whether the critters are munching on your rim joist, not because you suspect they are making tunnels in your insulation.

Answered by Martin Holladay, GBA Advisor
Posted Jul 20, 2014 4:35 AM ET
Edited Jul 20, 2014 4:36 AM ET.

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Martin,
I agree with what you said BUT add that the "critters" often use tunnels through foam insulation as a pathway to the delicious wood. BUT that is plastic foam, NOT Foamglass which they simply can't get into, let alone through. For the purpose of identifying insect paths to and from wood Inspecting the outside of the Foamglass is as good as inspecting under it.
Since Stacy is using a "slab on grade" there will be no rim joist but there will, no doubt, be other wood.

Answered by Jerry Liebler
Posted Jul 20, 2014 2:29 PM ET

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Thank you, Jerry and Martin, for your responses. Just to clarify, we already have the Foamglas and it has now been installed. We had to keep the inspection gap.

Answered by Stacey Owens
Posted Jul 26, 2014 9:13 PM ET

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Stacey,
Maybe you could get approval to insert cut strips of high density mineral wool in the gap(s). It would be easily removable for inspections but substantially close the thermal hole at other times. A variation of your "industrial strength Velcro".

Answered by Jerry Liebler
Posted Jul 26, 2014 9:26 PM ET

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Thanks, Jerry ~ I'll check! We are planning to use the Roxul ComfortBoard for exterior insulation so we will already have product on hand...

Answered by Stacey Owens
Posted Jul 26, 2014 9:36 PM ET

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