Duvall Passive House

This is a new house located in Duvall, a small town in NE King County. The clients were two teachers, one of whom, a high school physics teacher, took a 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+ 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!

2 thoughts on “Duvall Passive House

  1. Hi Jim,

    I emailed you couple years ago to design my passive house. You aren’t available during that time. Now, my house is under construction. Just wondering, if you aren’t using foams material, what other material can replace foams.


    • Hi Wendy-
      We just used dense-pack cellulose insulation in areas where often foam might be used. For example, where often a house like this without a basement would be slab on grade with rigid insulation underneath, here we did a crawlspace with cellulose insulation in the floor joists. Also in the exterior walls, rather than installing rigid foam insulation outside the sheathing, we did a layered wall with cellulose inside and out. This was a goal of the homeowner from the start – to not use any foam insulation, because of the GWP (global-warming potential) of plastic foams.

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