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TC Legend Homes: Everson Net Positive Home

Posted on Jun 9, 2020 in:
  • Case Studies

This award-winning TC Legend house is the 20,000th project certified by Built Green. As a 5-Star and Net Zero Energy certified home, it exemplifies how the Built Green program’s influence has grown and has been incentivizing sustainable building across Western Washington.

Set on 4.93 acres among Washington’s coastal wetland plains, this 2,538 square foot home in Everson, Washington recognizes the importance of conserving wetland habitats and the wildlife they support. Built on the only high spot, it looks south over heavily protected coastal prairie and wetlands.

Vital Stats



Location: Everson, Whatcom County
Star Level: 5-Star
Checklist: Single-Family/Townhome
Verifier: Ecoe Company
Site and Water 123
Energy Efficiency 252
Health and Indoor Air Quality 144
Material Efficiency 109
  Total Score 678


Strengthening the relationship between the house and its treasured wetlands, all roof water is collected from a zinc-free metal roof and piped from a central sump to splash blocks draining to the wetland. The central sump can also be directed toward the native planting and vegetable garden to reduce potable water use for irrigation. Taking full advantage of the home’s southern orientation, the 10.8 kW of roof-mounted solar panels produce a net-positive 4250 kWh surplus each year. Two roof overhangs from the clerestory design shade the southern-facing triple-glazed Vinyltek windows. Other passive strategies used to keep residents comfortable all year long include minimal glazing on the east and west facades.

TC Legend Everson Net-Positive home exterior, photo credit Zigzag Mountain Art

The home’s envelope consists of 6.5” SIP walls, a 10.25” SIP roof, and 4” foam under the mass of the concrete slab-on-grade, with the slab-edge stem walls encased in foam insulated concrete forms (ICF). The reduced second floor admits daylight into the center of the house, brightening the space, reducing glare from window walls, and connecting the inhabitants to the environment. This SIPs construction is a post-and-beam method that exposes the structural lumber details, resonating with its timber-centric Pacific Northwest setting. This structural detail is logical to the eye, and the wallet, and is replicated in the 8x8 exterior cedar posts and the complex kitchen beamwork.

Significant advances in home comfort are provided by the state-of-the-art heating and mechanical systems. The Zehnder Q600 heat recovery ventilator (HRV) wirelessly controls the in-line ComfoPost heating and cooling coil that is powered by the electric Chiltrix CX34 air-to-water heat pump to distribute conditioned air throughout the home via internal ducts. The whole-house battery wiring and Alexa-controlled blinds, lighting, and electronics ensure the home is future-ready for everything Mother Nature brings, while leaving only a light zero-emissions footprint.

TC Legend Everson Net-Positive home exterior with solar panels, native planting, and vegetable gardens, photo credit Zigzag Mountain Art
TC Legend Everson Net-Positive kitchen, photo credit Zigzag Mountain Art
TC Legend Everson Net-Positive kitchen and wine bar, photo credit Zigzag Mountain Art

Built Green Highlights

Site and Water

  • 100% stormwater infiltrated on-site
  • 58% of walkways, driveways, and patios are permeable
  • 80% of the 4.93 acres is undisturbed field grass and native prairie
  • Less than 3% of the lot is turf grass
  • Landscaping will be primarily fruits and vegetables and native plants
  • Western Red Cedar trees will provide a windbreak along the norther property line
  • 20% water-use reduction using all WaterSense-certified fixtures
  • 21% of lot granted in perpetuity to Whatcom County as conservation easement
TC Legend Everson Net-Positive home office, photo credit Zigzag Mountain Art
TC Legend Everson Net-Positive master bedroom, photo credit Zigzag Mountain Art

Energy Efficiency

  • Net-positive home with a HERS score of -19 and a 12.43 kW roof PV array
  • 4250 kWh surplus (net-positive) power (equivalent to 10,000 miles in an electric car at 2.6 mi/kWh)
  • Energy Star certified
  • Department of Energy Zero-Energy Ready certified
  • Blower door results of 0.47 ACH50
  • AeroBarrier air sealing
  • Substantial envelope insulation lowers heating requirement: R29 walls, R49 roof, R20 under slab, R24 slab-edge, U0.15 windows
  • Passive heating design strategies utilized
  • Chiltrix air-to-water heat pump for heating and domestic hot water with COP of 3.92
  • Triple-pane Vinyltek windows with U-values from 0.15-0.18
  • 100% LEDs
  • All Energy Star-certified appliances
  • Electric car charger installed in garage

Health and Indoor Air Quality

  • Indoor airPLUS certified
  • Upstairs flooring pre-finished and FloorScore certified
  • Solid wood cabinets with low-VOC finish
  • All low-VOC paints, adhesives, and sealants
  • Large roof overhangs on upper and lower floors
  • Zehnder HRV
  • No gas-burning appliances in house
TC Legend Everson Net-Positive master bathroom, photo credit Zigzag Mountain Art
TC Legend Everson Net-Positive HRV and utility/mechanical room, photo credit Zigzag Mountain Art

Materials Efficiency

  • Graphite SIPS for exterior walls and ceilings
  • Interior walls advanced framed
  • Leftover materials moved to next job
  • 75%+ of waste recycled
  • ICF foundation walls
  • Solid wood, domestically grown interior doors and trim
  • Standing-seam metal roof
  • Slab used as finished flooring on lower floor
  • Allura cement board siding with recycled content
  • Locally produced Vinlytek windows
  • Builder’s trucks run on biodiesel
  • Stepless first floor contains living areas, bathrooms, and bedrooms
TC Legend Everson Net-Positive home under construction—SIP roof, photo credit Zigzag Mountain Art
TC Legend Everson Net-Positive home under construction—slab-edge stem walls encased in foam insulated concrete forms (ICF), photo credit Zigzag Mountain Art

Photos courtesy Zigzag Mountain Art


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