Formula for frost protected “floor”?
Hello everyone..
I’m hoping to use foamed glass aggregate as the foundation for my pole-barn to prevent frost heave in Iowa.. Ive been reading about frost protected slabs, but the perimeter insulation requirements are vague or almost like one shoe fits all..
Are there any guidelines/formula’s where depending on the climate zone, determines the R value needed, and distance away from the structure the buried perimeter insulation needs to be? And when you insulate around the perimeter, how much R value do you need under the structure? Less insulation seems to be the safest so that heat from the structure can keep the ground above 32 degrees, but that doesn’t sound very energy efficient.. And what if I plan on leaving this structure unheated in February? How do I go about using foamed glass aggregate to prevent heave on a unheated polebarn In Iowa?
I feel the question is how far away from the structure insulation
is installed, but how much heat from the earth (can you rely on enough heat?) will I get to keep the soil above 32 degrees is another question..
Thanks!
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Replies
Mike,
Have you read this article? https://www.greenbuildingadvisor.com/app/uploads/sites/default/files/Frost-Protected%20Shallow%20Foundations.pdf
Mike,
This guide gives you all the information you need: https://www.homeinnovation.com/~/media/Files/Reports/Revised-Builders-Guide-to-Frost-Protected-Shallow-Foundations.pdf
No I haven't read either.. Thanks.
The article by Martin and table on page R403.3 of the IRC suggest at my location R5 extended 24" would protect a monolithic slab..
To me this doesn't sound like allot of insurance or a bare minimum, especially considering he doesn't mention unheated spaces..
The article Malcolm linked to by the NAHB Research Center goes much more in depth, and talks about unheated spaces. I'll have to spend more time reading that article..
Its to bad glavel costs $85 to $100 per cubic yard, about twice the cost of gravel and almost at much as concrete.. But its not like anything we've seen in a while at R1.7". Its to bad concrete didnt have that R value..