At my firm, Birdsmouth Design-Build in Portland, OR, builders and architects ask regularly if we can help them design high-performance assemblies that are well-above code, approachable for the average builder, and cost-effective for clients. The question seems eminently solvable, but on further inspection can prove tricky. Expanding this question to cover most climate zones in North America makes things even fuzzier. When GBA approached me to share a couple of our go-to details for the Expert Exchange program, my mind went straight to this conundrum. How do we share details that can be useful to broad swaths of people when there are so many variables to consider beyond climate zone including budget, availability of materials, and local trade knowledge, to name a few?
One thing that remains consistent no matter the conditions is the importance of getting the four control layers right. All our assemblies integrate strategies to control bulk water, air movement, vapor drive, and thermal losses—in that order.
For the purposes of this article—part one of two—I will assume most readers are fairly versed in controlling bulk water. I’ll jump to the next layer in line of importance: the air barrier. In most homes, the leakiest parts of the building are the top plate-to-roof connection followed by the bottom plate-to-foundation connection. Focusing on these two areas seems beneficial to the greatest number of people. I will share how our firm approached the detailing of these two locations on a new home we are building in Damascus, OR, climate zone 4C. Here, I will address the foundation-to-wall connection. In my next post, I will talk about the wall-to-roof connection.
A little backstory
Both assemblies are taken from a certified Passive House build. When designing and building to best practices, our firm uses the Phius 2021…
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