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Heating wall cob thickness

Posts: 484
Location: Englehart, Ontario, Canada
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Hi Ernie and Erica,

Thanks for the Guelph seminar in September. Things froze up here too soon to get much done. Am working on plans for a heating wall as Ernie suggested to me. Just wonderin', what thickness of cob from heat pipe to exterior would be the minimum you'd suggest?

Max Kennedy
Posts: 1278
Location: Okanogan Highlands, Washington
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Nice to hear from you Max!

If you want to follow the ASTM standard, it would be 5" cob (or 5" total masonry between the heat-exchange channel and the exterior surface), plus a 4" air gap to combustibles.
For just practical / structural purposes, about 4" of cob is about the thinnest most people can build successfully to support the hollow pipes inside a wall or bench. If you think of those 8" pipes as formwork for a masonry arch, you know you want the sides of the arch to be stout enough to keep that pipe from collapsing outward.


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