Passive House was the energy efficiency goal when ground broke on the Karuna House, a high-end residential project near Portland, Ore., in Yamhill County. Achieving those standards would take focused attention on the wall assembly, windows, doors, mechanical systems and foundation, all while accounting for the area’s commonly precipitous weather.
Luckily, the project’s builder, Hammer & Hand, was experienced in this energy standard and climate, and they had come to rely on systems and products that they knew could keep the job moving when rain was falling down.
They were particular about the building envelope, preferring a fluid-applied system over peel-and-stick house wrap made of paper.
“Installing a vapor-permeable peel-and-stick on wet wood throttles the wood’s drying potential and would have slowed the construction process and added cost for mechanical dehumidification,” said Skyler Swinford, then a project manager for Hammer & Hand.
In addition to the fact that both waterproofing products can be applied to damp surfaces – a huge plus to avoid rain delays – the vapor-permeable products stop air and water movement through the wall assembly – a key in the Passive House standard measured by a blower door test.
Since the house couldn’t afford any air leaks, and there was really not a lot the project team could go back and redo on the wall assembly if the blower door test results weren’t satisfactory, the team applied FastFlash and Cat 5 everywhere, even in places it doesn’t typically go, like the roof, over parapet walls and the undersides of cantilevered decks.
“We didn’t want to take any chances with the air-tightness of the building enclosure,” Swinford said.
Despite the extra work, the air barrier installation went faster than planned and took less manpower than expected, he said.
Their efforts paid off when a preliminary blower door test came in at 99.9%, even as installers were going around and spot-sealing the 14,000 square feet of air barrier surface of the house.
“Considering the complexity of the structure, I didn’t think the house would pass the air-tightness test on our first attempt,” Swinford said.