Project Description

Duvall Passive House

This was a new house located in Duvall, a small town in King County. The clients were two teachers, one of whom, a high school physics teacher, took a year sabbatical to act as the general contractor for the project. The site is in a rural area on the outskirts of town.

The homeowners goals for the project were to:

  • Build a Net-Zero Energy home (incl. an electric car – no utility or gasoline bills for the rest of time).
  • Use only renewable/ sustainable/ non-toxic materials (no foam!).
  • Make the project affordable.
  • Build something that would last for 100’s of years.
  • Help revolutionize the building industry.
  • Promote Passive Houses for all!

The house is two-stories with an attic, and no basement. It’s traditional in style, but very cutting edge in its performance:

  • R-50 walls, R-85 roof, R-38 floor
  • Sustainable materials (No foam)
  • Vapor open (drys to inside and outside)
  • No thermal bridging
  • Protected OSB air barrier
  • 2/3 Insulation outside of OSB (keep OSB above dew point)
  • Triple-glazed windows
  • Space heating by ductless mini-split heat pumps
  • Heat recovery ventilator for fresh air
  • Heat pump water heater
  • 10 kW PV array

Passive House stats:

  • Space Heating – 3.12 kBtu/s.f/yr (below req’d. limit of 4.75)
  • Primary Energy – 25.8 kBtu/s.f/yr (below req’d. limit of 38)
  • Blower door test results – 0.40 ACH at 50 Pascals!