Q We have a cabin in northern Wisconsin that we close up in November and open up in May. We shut off the water and put RV antifreeze in the drains but leave the heat on with the thermostat set at 55 degrees. We'd like to turn the heat off completely as our propane bills are high, but I thought I had read that if a cabin has a foundation (which ours does), you cannot do that.
A The term "cabin" is a loose one. Once it meant a primitive summer place. Barely finished, it may have a bathroom, but did not have insulation or the fit and finish of a primary residence.
Now a "cabin" can mean a completely modern, year-round home, fully finished and equipped with every convenience -- basically, a second home. There's a lot more at risk when you turn off the heat in "cabins" like these. The damage from frost and broken water pipes can be tremendous. Floors, walls and ceilings can twist and buckle. Wood doors and trim warp and splinter; foundations can heave. Repairs can run thousands of dollars.
If that's your cabin, consider installing a thermostat that will permit lower temperatures of 40 or 45 degrees.
Although it's not a good idea to completely shut down the heat in a house, in some cabins it can save a lot of money and greenhouse gas emissions over a winter, said state energy specialist Phil Smith. But it's a gamble, he added.
To reduce the risk of damage, Smith recommends that you continue your winterization steps, but also:
Insulate the above-grade foundation on the exterior to a foot below grade and then extend the insulation out and away from the foundation by 2 feet, forming a continuous apron of insulation to retard penetration of frost in the soil. Consider an R-value of 10. You can extend the insulation down the entire depth of the foundation wall, but the apron is very important for retarding frost penetration into the soil overall. (The State Energy Office publishes a free guide to basement insulation, including illustrations. Go to www.commerce.state.mn.us and type "basement insulation" in the search window in the upper right corner.)
Also, insulate the interior of the basement from grade level up to and including the rim board. Consider an R-10 rigid foam cut to fit and caulked in place for the rim board. Install an R-value of 30 across the ceiling. The goal is to make an insulated box of the foundation system and floor, those parts of your cabin you want to protect.
If the cabin has a crawl space, an additional step is to seal the exposed earth with poly sheeting sealed at all seams and joints. This action will help contain the deep soil temperature in the basement or crawl space by establishing a thermal boundary to the exterior. Remember, soil has insulating value. This application of insulation is an attempt to replicate the thermal performance of the soil, reducing frost penetration.
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