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Dwell Development: 5-Star Net Zero Energy Homes

Posted on May 4, 2021 in:
  • Case Studies

Along a few blocks on Bagley Ave. N there are three new Built Green 5-Star certified homes by Dwell Development. Designed with energy efficiency in mind, as well as homeowner comfort, all of Dwell’s projects include their standard sustainability features such as triple-pane windows, double 2x4 walls, and heat recovery ventilators (HRVs).

Vital Stats



Location: Seattle
Star Level: 5-Star, Net Zero Energy Label
Checklist: Single-Family/Townhome
Verifier: Evergreen Certified
Site and Water 136
Energy Efficiency 255
Health and Indoor Air Quality 161
Material Efficiency 108
  Total Score 719

By framing their walls with two 2x4s, they have the flexibility to stagger studs so they do not align, reducing the potential for thermal bridging. Thermal bridging occurs when a more conductive material (such as a wood stud) provides a direct path between the cold outside air and the warm inside air. By staggering 2x4 studs, Dwell is able to break up that path with a cavity of insulation, which helps to minimize that transmission. They are also able to leave a gap between the two walls and change how thick their walls are.


For the Bagley projects, the walls are roughly 10 inches thick and completely filled with blown-in cellulose insulation. Having such a thick, well-insulated exterior wall makes these houses very quiet and easily able retain to heat or cold produced by the HVAC system.

Although the three houses are composed of two different projects, all three units are heated using ductless mini-split heat pumps, with Envi wall heaters as supplemental heat. Water heating is done via a hybrid heat pump water heater with a temperature-based recirc system. Since all of Dwell’s houses are 100% electric, homeowners can offset all their energy usage by adding solar panels; Dwell prewires for solar.


In fact, one of the Bagley houses included a 14.25kW solar system, which made the final HERS score -2. This means that the house produces more energy than it uses! This offset was possible by keeping the home’s loads (how much energy the home needs) low with Energy Star appliances, including a washer/dryer; 100% LED lighting with installed dimmers; an induction range; and previously mentioned features.

In addition to energy efficiency measures, Dwell also focuses heavily on making houses safe and healthy. All their houses use low- to no-VOC products and have no carpet installed, which allows for better indoor air quality. They also install HRVs that constantly supply the houses with fresh filtered air!


Built Green Highlights

Site and Water

  • 100% pervious hardscaping
  • Drought-tolerant landscaping
  • Minimal turf grass
  • Low-flow plumbing fixtures
  • High-efficiency 0.8 GPF toilets

Energy Efficiency

  • 37% and 41% better than code
  • Energy Star certified houses
  • R-20 sub-slab insulation
  • Blown-in cellulose walls and ceiling (~85% recycled content)
  • Blower door scores less than 2.0 ACH
  • Liquid applied air and weather barrier

Health and Indoor Air Quality

  • EPA Indoor airPLUS certified
  • No carpet in the units
  • Garages with motion sensor exhaust fans
  • Rainscreen under siding
  • Heat Recovery Ventilators

Materials Efficiency

  • Abundant use of local and regional materials
  • Polished concrete slab floor
  • Bamboo composite decking
  • Metal roof installed
  • Recycled content insulation


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