In three new videos produced by Oregon builder Hammer & Hand, lead carpenter Val Darrah explains how he keeps air sealing in mind as he frames the walls for his current project, the Pumpkin Ridge Passive HouseA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates..
Val explains why he prefers to use a router rather than a saw when he cuts out window openings in the OSB sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen.
. He also shares his method of building window bucks out of 3/4-inch plywood.
The OSB sheathing seams are treated with Prosoco R-Guard products: Joint and Seam Filler for the seams, and FastFlash for the inside of the window rough openings. Val explains that in damp weather, it’s easier and more effective to seal sheathing seams with Joint and Seam Filler, a moisture-cured sealing product, than with air-sealing tape.
The concrete foundation will be insulated on the exterior with 6 inches of expanded polystyrene (EPS) foam.
For more information on the Pumpkin Ridge Passive House project, visit this page on the Hammer and Hand website.