Known for their market-leading sustainability, Dwell Development recently completed the first home to receive the new Built Green® Net Zero Energy Label. This single-family home sits adjacent to Genesee Park and features Dwell's typical recipe of reclaimed materials and high-performance envelope, and introduces some new additions to the mix.
Vital Stats
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Section
|
Points
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Location: Seattle
Star Level: 5-Star, Net Zero Energy Label
Checklist: Single-Family/Townhome
Verifier: Evergreen Certified |
Site and Water |
150 |
| Energy Efficiency |
261 |
| Indoor Air Quality |
141 |
| Material Efficiency |
100 |
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Total Score |
682.5 |
Net zero energy homes are required to offset all energy they consume annually with renewable energy produced on-site. Typically, on-site generation is achieved through solar photovoltaic (PV) panels. Dwell did use a 9.9 kW array in this project, but also added a Silk Road solar thermal system to provide solar-heated water to the domestic hot water system. The unique evacuated tube collectors in this system are designed to work on cloudy Pacific Northwest days, since they absorb mostly UV-spectrum light. Silk Road has also made advancements in circulating fluid to eliminate the historical challenges of the fluid freezing or boiling. According to the HERS energy model for the project, the solar thermal system offset about 3,000 kW of PV panels that would have otherwise been needed to get to HERS 0 (net zero) and did so at a much lower cost.
The cost of PV panels has decreased significantly over time but can still be a relatively expensive home component. Therefore, the best strategy to build net zero energy is to first lower the home's loads (aka how much energy the home needs) as much as possible to reduce the size of the required PV system. To this end, Dwell constructed the home with R-42 double stud walls, an R-71 roof, and an R-20 heated slab floor. Triple-pane windows, a Zehnder HRV for balanced ventilation, and an air tightness of 1.0 ACH50 round out the major energy efficiency measures. Space heat is provided through heated floors using an ultra-efficient Chiltrix air-to-water heat pump.
To achieve Built Green 5-Star certification, a project must also incorporate numerous credits in the material efficiency, indoor air quality, and site and water categories. The team was able to retain several tall trees on-site and used 100 percent pervious paving and hardscaping. The heat recovery ventilation system provides fresh air and exhausts stale air 24 hours a day and the home's sleek modern aesthetic is juxtaposed with extensive reclaimed wood flooring and siding.
Built Green Highlights
Site and Water
- Five large trees retained on site.
- 100 percent pervious hardscaping.
- Minimal turf grass.
- Low-flow plumbing fixtures.
- Drought-tolerant landscaping.
Energy Efficiency
- Super-insulated building envelope.
- Chiltrix reverse chiller for radiant heat.
- Solar thermal domestic hot water system.
- 9.9 kW solar PV array.
- 1.0 ACH 50 blower door test score.
- Zehnder HRV (heat recovery ventilation).