Quick Answer
Foam insulation can be used in a cordwood cabin, but it's essential to ensure compatibility with the unique characteristics of cordwood masonry, such as high moisture content and irregular wall cavities.
Choosing the Right Foam Insulation
When selecting foam insulation for a cordwood cabin, look for products with high moisture resistance and a high R-value (thermal resistance). A popular option is XPS (extruded polystyrene) foam, which has an R-value of R-5 per inch and can withstand moisture levels up to 75%. However, XPS foam is not recommended for areas with high humidity or direct exposure to rain. A better choice might be spray foam insulation, which can be injected into tight spaces and has an R-value of R-6 per inch.
Installing Foam Insulation in Cordwood Walls
To install foam insulation in cordwood walls, start by drilling holes in the log ends for the foam to fill the wall cavities. Use a drill bit with a 1-inch diameter to ensure a snug fit for the foam. Then, use a foam gun or a spray foam can to inject the foam into the walls, making sure to fill the cavities completely. Be cautious not to overfill, as excess foam can compress and lose its insulating properties.
Mortar Mix and Foam Insulation Compatibility
It’s crucial to use a mortar mix that is compatible with foam insulation. A mix with a high cement content, such as a 1:1:6 or 1:1:8 ratio of cement to sand to lime, will help prevent the foam from degrading over time. Also, make sure to apply a vapor barrier between the foam insulation and the cordwood walls to prevent moisture from entering the wall cavities. This will help maintain the integrity of the foam and prevent damage to the cordwood structure.
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