Foam insulation for Sonotubes
PhilTheThrill
| Posted in Green Building Techniques on
I do not see any reason why insulating around a Sonotube would not allow one to avoid having to excavate below the frost line for a footing.
Am I missing something?
Thanks.
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Replies
The physics are similar to those for unheated structures with FPSFs. Because the buildings--or piers--are not heated, the foam would need to extend far beyond the piers.
In my area, CZ6 in central/southern Maine, unheated structures need 5' frost wings at the building corners. The pier would conduct heat from the ground so you would need either thicker than normal or even wider than 5' wings to keep the ground below from freezing. It's hard to imagine a scenario where that would be easier or less expensive than digging a little deeper, but I'm sure they exist.
Thank you: that explains the reason, then, it’s not common practice.