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TC Legend Homes - 5-Star Net Zero
Energy Single-Family Homes

TC Legend Homes
Vital Stats
Location: Seattle
Star Level: 5-Star
Checklist: Single-Family New Construction Checklist (2014)
Verifier: Evergreen Certified
SectionPoints
Built Green Team4
Site and Water140
Energy Efficiency231
Indoor Air Quality108
Material Efficiency101
Homeowner Education11
House Size Multiplier1.05
Total Score624.75

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Developer Victory Partners and builder TC Legend Homes have completed two stunning examples of healthy, sustainable and energy efficient single-family homes. Located on two peaceful wooded lots in the Victory Heights neighborhood of Seattle, the outward appearance of these 5-Star dwellings belie their advanced construction and ultra-high performance. The homes are constructed using Structural Insulated Panels (SIPs) which is one of the trademarks of builder Ted Clifton, a leading figure in the net-zero energy building community. SIPs are a completely different way of building the walls and roof of a home. Unlike a traditional wall consisting of 2x6 studs, top plates, and bottom plates, SIPs are large pre-manufactured panels of rigid EPS foam sandwiched between two layers of oriented strand board (OSB). This allows a home to more easily reach high levels of air tightness while also reducing the thermal bridging that occurs with traditional framed walls. Indeed, the blower door test for these homes showed they both meet the notoriously rigorous Passive House air tightness standard of 0.60 ACH50. Couple this with carefully controlled mechanical ventilation and the results are a highly comfortable, efficient and healthy home.

Heated with 100% in-floor hydronic systems, the homes provide a quiet and comfortable living environment. Distributing heat using hot water is great way to provide space heat but the efficiency of such a system depends largely on how the water is heated. In this case, that heat is initially provided by the sun. An evacuated tube solar thermal unit pre-heats water for both the hydronic heat as well as domestic hot water. When the sun is not shining, hot water is created by a Thermo Matrix air-to-water heat pump that boasts a Coefficient of Performance of 4.5. This means for every unit of energy put into running the heat pump, it creates 4.5 units of heat output. As a comparison, most mini-split-type heat pumps operate in the range of 2-3 CoP.

But the crowning component on these homes is the massive 9.5 kW solar arrays sitting on each roof. Unlike a zero energy ready home, these homes are already producing their own electricity. In fact, energy modeling has shown that they will produce more energy on an annual basis than they consume. That excess energy can be used to charge an electric car via the pre-wired 240v outlet in the garage.

Rainwater is infiltrated 100% on site using pervious concrete and an in-ground catchment basin. Numerous large trees were preserved on site, most notably the 70+ foot Cedar in front. Interior finishes include exposed concrete slab floors, low VOC finishes, and a unique salvaged pantry door that was once the front door of the pre-existing home on the property.

Here is a quick breakdown of the strategies that got these homes to 5-Star Built Green:

Site and Water

  • Numerous large trees retained in both back and front yards
  • All rainwater is infiltrated on site using pervious concrete and a dry well catch basin
  • No pressure treated lumber used in landscape
  • Niagara Stealth 0.8 gallons per flush toilets

Energy Efficiency

  • Net positive energy via 9.5 kW PV arrays
  • Evacuated tube solar hot water
  • 4.5 CoP air to water heat pump running 100% in-floor hydronic heat
  • SIP wall and roof construction
  • Triple pane U-0.21 windows
  • 0.60 ACH50 air tightness
  • 100% LED lighting

Health and Indoor Air Quality

  • Continuous exhaust ventilation with filtered makeup air
  • Low VOC paints, adhesives, and finishes
  • Induction cooktop - no gas appliances in house

Materials Efficiency

  • SIP construction - premanufactured panels
  • Salvaged finish items including re-use of front door from preexisting home
  • Extensive local materials used
  • Exposed concrete floors

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Photo credit: Decora Photography

Use pervious surfaces to reduce rainwater runoff