SIPs Construction

Whatcom County Net Positive - 2019 Department of Energy Award Winner

Photos by Scott Miller, Elevate Pro Photo

Photos by Scott Miller, Elevate Pro Photo

This Built Green Five Star home in Whatcom County was selected as a Department of Energy 2019 Housing Innovation Award Winner!

The house is weighted south, toward the sun. With both asymmetrical roofs; longer to the south for solar build-out and a preponderance of south glazing for wintertime passive harvesting, the windows are appropriately shaded, with regionally appropriate eaves and porches, against summertime overheating.

The gross footprint of the house is rectangular, stretched with the long-axis running east-west to maximize space available for solar harvest on roofs and south wall, with much smaller east and west walls which overheat as they take the full force of the sun in summer. The slab-on-grade floor is finished to be left exposed and imparts a visceral, cooling, underfoot mass.

The slab also houses in-floor hydronic heating and radiates warm comfort during the long winter season, which, like all the seasons, can be felt and seen keenly in this house though the diversity of landscape views.

The home also features an open floor plan, with no wasted hallway space. The living area loft provides a sense of grandeur, but the modest-sized bedrooms and bathrooms require less energy and provide balanced efficiency.


  • 2707 Square feet (conditioned)

  • 4 Bedrooms

  • 2.5 Baths

  • SIPs construction

  • 10.066-kW Solar

  • Triple-pane windows

  • Air-to-water heat pump

  • In-floor hydronic heating

  • Heat Recovery Ventilator

  • Electric car-charging

  • Low- or no-VOC products sourced throughout.

  • Wood posts, beams, counters, interior and exterior trim details milled on site from local timber

West Seattle 2018 Award Winner

Photos by Yuriy Manchik

Photos by Yuriy Manchik

This is a Built Green Emerald Star home in West Seattle. It was the first Emerald Star home for TC Legend and the second of its kind built in Seattle! It is also a Department of Energy 2018 Housing Innovation Award Winner and Built Green’s “Green Hammer” Project of the Year!

This floorplan is flexible into the future, with two extra bedrooms already in the program, fitted with egress windows & minimum floor area to meet code; One will partition behind the utility, the 2nd can partition from the recreation room upstairs. So this 3 bedroom main house can grow to 5 bedrooms in a day!

The energy-shell is a simple rectangle, conforming to and ideal 1:1.6 established ratio for temperate environments. SIPs shell construction is post & beam type of load-bearing construction that means internal walls can be moved easily during the life of the building as they carry no load. The post & beam structure is visible as both architecture and a celebration of the woodcraft of the Pacific Northwest.


  • 3,160 Square feet

  • 4 Bedrooms

  • 4 Baths

  • 9.9-kW Solar

  • Triple-pane windows

  • 10,000-gallon rainwater storage

  • Air-to-water heat pump

  • 2 electric car charging stations

  • Low- or no-VOC products sourced throughout. No PVC.

Victory Heights Net-Zero Home

This Built Green 5-Star zero-energy home defines the Seattle eco-lifestyle. It features an open floor plan, heated hardwood floors, 9-foot ceilings, and exposed beams.  On the roof, a 9.5kW net-metered solar array provides all the home's power needs, and an electric car charging station is built into the garage. Triple-pane windows and SIPs construction offer plenty of insulation, and a whole-house filtration system keeps the air pure. Designer touches include Hinkley lighting, custom cabinetry, Carrara marble countertops, stainless steel appliances, an induction cooktop, and a 9-foot kitchen island.


  • 2,426 Square feet

  • 4 Bedrooms

  • 2.5 Baths

  • Radiant heat

  • Air-to-water heat pump

Bellingham Power House

Bellingham Power House Exterior

There's nothing we love more than building overachieving homes. This remarkable home not only produces enough solar electricity to meet its own energy needs, but it produces surplus power to charge two electric cars.

Nicknamed the Power House, it is the first of its kind in Whatcom County. The home sends power to the city’s electrical grid when the sun is out and draws it during the night or on cloudy days. (Contrary to popular belief, the Pacific Northwest is an excellent place for solar). Averaged over the entire year, the panels will produce more power than the house uses, with enough of a surplus to power two electric cars through on-site charging stations.

The house qualifies for a one-time federal tax credit of approximately $10,500 and Washington State solar production credits of approximately $5,000 a year until 2020.

Perhaps more remarkable than the home’s efficiency is its modest price tag. Shared by two couples and three children, the 2,700-square-foot custom home cost under $150 per square foot to build, significantly less than most other residential construction projects in Bellingham. 

With its airtight shell, structural insulated panel (SIP) construction, numerous south-facing windows and passive solar design, highly efficient heat pump, solar hot water, and a solar PV array using Bellingham-built ITEK modules, this one-of-a-kind house has no electrical bills (other than the monthly service charge for this  grid-tied system) and costs nothing to heat. No oil, natural gas, or other fuels are used. 

This home shows that cutting-edge energy efficiency technology can actually be made affordable by eliminating entire categories of expenses, like heating and gasoline bills. And if one house can be shared by two families, expenses are decreased for both.


2,700 square feet, co-housing duplex for 2 families, 2 stories, 3 bedrooms, 3 bathrooms, 3 multi-purpose rooms: loft, rec room and sunroom, semi-covered deck, covered parking, acid-stained concrete slab foundation, radiant-heat floors, exposed beams, Hardie plank & milled cedar siding, metal roof, solar hot water, 9.9 kW solar array, 2 electric car charging stations.

  • Powers itself and two electric cars, for net-zero emissions, over the course of a year

  • Uses a 9.9kW photovoltaic system (half power goes to the house, other half powers two cars)

  • Envelope includes structural insulated panels, insulated concrete forms, and 4” foam under slab

  • Heat and hot water provided by a solar hot water collector with an air-to-water heat pump backup

  • South-facing high solar gain triple-pane windows and solar absorbing concrete floors

  • Utilizes the most energy-efficient appliances and lighting available on a budget

  • Collects rainwater for all outdoor water usage and utilizes low-flow fixtures indoors

  • Provides housing for four adults and three kids with enough garden space to feed both families

  • Budget under $150/SF includes all development costs except land (built on an infill lot in the city)

  • Northwest Energy Efficiency Alliance is monitoring home for US Department of Energy pilot program

  • Fresh air provided by heat recovery ventilator and earth tube combo system

  • HERS rating is -15

Issaquah Rental Home

Rick had plenty of building experience, so when he decided to construct a detached accessory dwelling unit (DADU) on his large lot in Issaquah, he wanted it to be a hands-on project. TC Legend Homes built the highly insulated SIPs shell, and Rick took it from there. These photos show what an excellent job he did with the finish work. While the home does not have solar panels installed yet, it is oriented to make the future addition of PV simple.

We like this project because it shows how an owner who wants to get involved can save on construction costs and still end up with an air-tight, well-built structure that will last for generations. We also like how Rick made excellent use of his beautiful treed lot, adding another home near his main residence that will bring him rental income and add value to his property.