Log home heat loss
I am currently working on a project that the homeowner has asked me to help size a replacement furnace for a log home. Currently the home is heated by an outdoor woodstove, which used 15 cord last year. The outdoor stove heats water which moves to a water to air exchanger in an LP gas forced air furnace. The gas is used only as emergency heat. I’m planning on conducting a blower door test. (Last log home blower door test I conducted was 19 ACH50!) There is some roof repair that needs to be completed, should be able to figure out the R-value in the roof at that time. I believe the roof is insulated with 4 inches of polyiso, 1980’s vintage. My understanding is that older polyiso looses it’s R-value over time. The walls are 10″ to 16″ hand scribed logs.
Question is in calculating R-value of mass log wall. Should I use an average log diameter or is there some other way in calculating log R-value?
Home is located in zone 7. Homeowner is hoping to use a storage electric furnace on an off-peak electric program but furnace will only store 800,000 BTU’s. I have a feeling that’s not enough for this home. May suggest a cold weather heat pump with modulating LP gas forced air furnace. No natural gas available.
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