I’m getting ready to build my first
RMH. The mass top will sit at floor level, 7 ½ by 8 feet
footprint.
In February and March 2017, ---an extraordinary year for rain and snow in the Boise River basin--- I had
water 8” above the base of my future heater mass. So I’m thinking of setting an outside row of
concrete blocks, in cement mortar. Two of the four sides butt up against, or rest on, interior footing walls, so I’m not as concerned about settling and cracking. Or
should I lay a concrete footing under the blocks spanning that 7.5 feet?
I’m concerned about heat transfer through ground moisture, so I think a vapor barrier will be a good idea. I thought it’d go inside the block wall.
Then, I’m thinking of lining the ground with perlite, an inch thick? reducing heat transfer into the Earth. I should also line the concrete footings with perlite. I guess, I dont know!
What do you folks in the know think?
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