The biggest enemy of buildings is moisture, and that's even more so with strawbale buildings. So it's very important that we get key details, like window and door openings, right.
Let's start with the goals of our walls: - Being in a cold climate (climate zone 6a), we need to maximize the insulation value of the strawbales. - The post and beam structure needs to support the building. - Indoor and outdoor plaster layers retard moisture and suppress fire risk. - Windows and doors bring light, ventilation, and access. - All materials are as natural (not fossil fuel-based) as possible. To accomplish these goals has required a bit of design gymnastics, with the outcome being the following: - post and beam structure will be on the INSIDE of the structure. Wood has a lower R value (insulative value of ~1/inch) than strawbales (R value up to 2.38/inch), and thus wood on the outside would serve as a thermal bridge. By continuing the straw continuously around the envelope, we're maximizing heat retention. - windows need to be located toward the outside of the wall. This reduces horizontal surfaces and thus the risk of moisture intrusion. - With the post and beam structure on the inside and the windows toward the outside of the wall, we needed to find a way to support the windows. The outcome is a box-beam header that bridges the 1.5' gap cross the wall between the window and post/beam. The one bummer with this solution is that it requires plywood, a material that includes synthetic glues. However, this was the best option give the structural and moisture deflection needs. Example below of how a box beam is built. Basic 2x4 consturction that will be filled with insulation and topped/bottomed with plywood.
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AuthorKatie Jones and Peter Schmitt chronicle their building adventure. Archives
January 2024
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