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|Vital Stats |
|Location: Seattle |
|Star Level: 5-Star |
|Checklist: Single Family |
|Verifier: Tadashi Shiga, Evergreen Certified |
|Section ||Points |
|Site and Water ||130 |
|Energy Efficiency ||127 |
|Indoor Air Quality ||127 |
|Material Efficiency ||98 |
|House Size Multiplier ||1.1 |
|Total Score ||530 |
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A diamond among gems, this Built Green 5-star home in the cutting-edge Columbia Station micro-community has also achieved the formidable Passive House certification. Passive House-certified buildings must be extremely air tight, well insulated and must meet rigorous requirements for energy use and heating and cooling needs. Built by Dwell Development, the project benefited from extensive involvement by Evergreen Certified and Brute Force Collaborative. It is the first speculative home and first infill home built to the Passive House standard in the Northwest.
In order to achieve the Passive House net-energy standard, this home features super-insulated building elements, highly efficient windows, a compact form designed to maximize winter solar gain and elimination of thermal bridging through innovative framing techniques. This has resulted in a very comfortable building that requires little active heating and cooling and uses up to 90-percent less energy than an equivalent code-built home.
Building a home to Passive House standards requires using materials and building techniques that are foreign to most homebuilders. Dwell Development has built numerous homes in this new community to similar standards, so the jump to Passive House certification was a less significant change for the team in terms of materials, techniques and processes. In fact, "it was the next logical step" says Anthony Maschmedt of Dwell Development, adding "it's the right way to build a house." Besides their ultra-high-performance home, the owners enjoy its beautiful modern architecture, clean lines, modern finishes and large rooftop deck - attributes that have become Dwell's signature.
Walls feature a double 2x4 construction at 14" thick with dense-pack cellulose insulation. The roof is an 18" open web-wood joist with dense-pack cellulose, plus 2" of closed-cell spray foam. Both walls and roof are sealed with a fluid-applied weather resistant barrier (WRB). The slab is thermally broken by 4" of extruded polystyrene (XPS) rigid foam.
- Annual Space Heating Demand: 4.50 kBTU/ft²/year
- Primary Energy Demand: 31.2 kBTU/ft²/year
- Airtightness: 0.58 Air Changes per Hour at 50 Pascals
- Slab on Grade R-value: R-42
- Exterior Wall R-value: R-45
- Roof R-value: R-60
- Window U-value: U=0.17
- Center of Glass U-value: U=0.11
- Glass Solar Heat Gain Coefficient: SHGC = 49-62%
- PV required to offset electrical usage: 3.25 kWp
In addition to the attributes demanded by the Passive House standard, this 1,900-square-foot home has a host of sustainability and performance features.
Site and water
As part of the Columbia Station micro-community, the home is located within walking distance of shops and services and is only a few blocks from a light rail station. The site features pervious paving and rain barrels for landscape irrigation.
The home has a very low energy demand (31.2 kBTU/ft2/year) as required by the Passive House specification. Appliances are all Energy Star rated, lighting incorporates LED and CFL bulbs, water heating is accomplished through a gas on-demand system and an induction cooktop ensures low energy consumption. Triple pane windows built by Intus feature very low thermal conductivity across the frame and glass with a high SHGC. The heat transfer and solar gain properties for each window were strategically chosen based on its orientation in the home. Exterior shading prevents overheating during warm temperatures.
Indoor air quality
With an airtightness of 0.58 ACH at 50 Pascals, ventilation in the home is paramount and is achieved with a Zehnder Comfoair 350 Heat Recovery Ventilator (HRV). A Fujitsu mini-split heat pump provides space conditioning when needed. Zero-VOC paints and finishes are used in the home and trim, millwork and insulation are all free from added urea formaldehyde.
Highlights include reclaimed fir flooring sourced from old structural beams and Novustone countertops featuring 85-percent post-consumer recycled content - some of which is actually glass elements from Glassy Baby production scraps. Abodian cabinetry in the home is created with no added formaldehyde in a highly efficient low-waste manufacturing process.
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|Photos courtesy of Tucker English |