Small in size but high in quality, this net-positive DADU is a recent winner of a 2021 Dept of Energy Housing Innovation Award, as well as the 2021 Built Green Hammer Project of the Year Award. Constructed for future generations of the homeowner’s family, this 500 SF home will provide a comfortable, efficient dwelling for many years to come.
Vital Stats
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Section
|
Points
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Location: Seattle
Star Level: 5-Star, Net Zero Energy Label
Checklist: 2018 Single Family/Townhome
Verifier: Evergreen Certified |
Site and Water |
132 |
| Energy Efficiency |
230 |
| Health and Indoor Air Quality |
150 |
| Material Efficiency |
106 |
| |
Total Score |
731 |
Built in place of an existing garage, the concrete slab was saved and reinforced for the new 2-story structure. Targa Homes was able to use an almost entirely FSC-certified framing package; wood harvested from the highest level of responsibly managed forests. The living unit is substantially airtight using a high-grade housewrap with taped seams as well as AeroBarrier air sealing process. Blower door testing showed the home to be under passive house (PHIUS) required air tightness of 0.05 CFM/SF of envelope. Triple pane windows and blown-in fiberglass insulation complete the above-code envelope.
Targa used a unique combined heating/cooling and ventilation device in this home called the Minotair Pentacare V12. This advanced machine brings in fresh air and exhausts stale air, much like an HRV/ERV, but with an internal heat pump it also heats and cools the living space. Appropriate for smaller, low load homes like this, it’s the only HVAC equipment needed. The Pentacare also features HEPA filtration. Airtight homes paired with fresh filtered outdoor air result in superior indoor air quality which is a focus for Targa Homes.
With an optimally pitched, unshaded South-facing roof, Targa was able to convince the homeowner to invest in a 5.85 kW solar PV array. Modeling and HERS rating by Evergreen Certified showed that this would be net-positive energy home, providing more than the total power needs for the all-electric home on an annual basis. That extra power is allowed by Seattle City Light to be put toward the main homes usage or can charge the new EV that the owners bought after construction was complete.
Interior finishes were chosen with an emphasis on sustainability and indoor air quality. Comfortable cork flooring runs throughout the home and sustainably manufactured Paperstone countertops were chosen for the kitchen. All paint and coatings are low or zero VOC.
Targa meticulously source-separates construction waste for recycling, including plastic film and styrofoam which are accepted for recycling at King County waste facilities.
