This 1,340 square-foot single-story, south-facing rural home was built for a professional couple in western Washington in 2018. It features an additional 576-square-foot attached garage to the north. The unheated garage, which sits outside the SIPs shell, is stick framed to reduce building and energy costs.

The home’s two offices are permitted as legal bedrooms, so it’s really a three-bedroom, two-bath net-zero rambler with a huge south-facing roof that has space for enough solar panels to power two electric cars and run the house.


  • Department of Energy Net-Zero certified
  • Fujistu 9RL minisplit heat pump
  • 100% on-site storm water infiltration via 40-foot dispersion trench
  • 70 trees and 160 shrubs were planted that will grow a forest on site
  • 10.8 kW of solar panels installed
  • 6.5” R-29 SIPs walls
  • 10.25” R-49 SIPs roof
  • 4” R-20 foam under 4” concrete slab-on-grade for thermal mass
  • 5.5” foam (total) R-23.8 insulated concrete form perimeter stem walls
  • Vinylek Boreal series triple-pane windows (U values of 0.14 to 0.16)
  • 1:1.6 aspect ratio floor plan, with the long side facing south
  • Minimal east and west glazing


Bellingham Gentle Density DADU

Bellingham Gentle Density DADU

TC Legend Homes demolished an existing one-car garage and re-purposed the available space with a cozy, high-performance, 775 square foot, detached accessory dwelling unit (DADU) that includes an attached single-car garage. The RE Store handled the structure demolition to maximize recycling opportunities and minimize waste.

The DADU was designed from the ground up to be net-positive-energy, meaning it will produce more energy on an annual basis than it requires. TC Legend Homes applied the same approach and many of the same building techniques to this DADU as it does to any of its other homes.

Key Features

  • A simple design to minimize exposed surface area

  • Orientation and window placement to optimize active and passive solar

  • Slab on grade with 4” under-slab insulation & Insulated concrete forms

  • Structural Insulated Panel construction (vice traditional framing) to reduce possibility of thermal bridging

  • Triple-pane windows

  • High-efficiency mini-split heat pump for heating & cooling and high-efficiency heat pump for water heating

  • HEPA High Efficiency Whole House Insulated Filtration System

  • 5.4kw photovoltaic solar system

  • Energy Star, EPA Indoor airPLUS, and 5-Star Built Green Certified

  • Home Energy Rating System (HERS) Index is negative 16!  (A typical new home has a rating of + 62).

Whatcom County DADU

Whatcom County DADU

 All photos courtesy of Jared VanderGriend

This family needed some room for the big kids to spread out. TC Legend Homes designed and built this accessory dwelling unit to meet their needs. The family gained a large garage, with 576 square feet of living space perched above, accessible to the main house via 2nd-story bridge.

Key Features:

  • A simple design to minimize exposed surface area

  • Orientation and window placement to optimize passive solar

  • Insulated concrete forms

  • 2nd floor Structural Insulated Panel construction (vice traditional framing) to reduce possibility of thermal bridging

  • Double-pane windows

  • High-efficiency mini-split heat pump for heating & cooling

  • Energy Star, EPA Indoor airPLUS, and 4-Star Built Green Certified

  • Home Energy Rating System (HERS) Index is 46.  (A typical new home has a rating of + 62).

Heintz Affordable Net-Zero-Energy Home

Heintz Affordable Net-Zero-Energy Home

Net-zero on a budget: A 1,055-square-foot home in Bellingham, WA that, features high-efficiency appliances, a balcony, a greenhouse, a patio, a loft, tongue-and-groove pine ceilings, and solar photovoltaic panels—all for $151,908 or $144 per square foot (not counting the land). A 3.2-kW PV system is all it takes to power the home, thanks to a highly insulated building envelope and high-performance equipment.

This custom net-zero-energy home, built for a Bellingham couple nearing retirement, won the grand prize in the Affordable category at the U.S. Department of Energy’s Housing Innovation Awards.  

The house is small but spacious feeling. It utilizes passive solar heat gain during the cold months, and is net-zero. (The photovoltaic energy annually produced equals all the energy annually consumed, including gas.) Best of all, it is very affordable. This home, a collaborative design effort between TC Legend Homes and the homeowners, was intended to demonstrate an alternative to ultra-expensive, extravagant “green” homes commonly seen. A net-zero home which is truly affordable for the average person perhaps has the greatest potential for conserving our planet’s resources.

The footprint is only 630 square feet, but the added loft brings that up to  about 1,000 square feet of living space. The foundation is constructed from insulated concrete forms (ICFs) with a concrete slab-on-grade floor. A waterproof concrete with premixed dye was used. Four inches of rigid foam under the slab provides insulation from the ground. This floor serves as a thermal mass during sunny winter days, absorbing and storing the sun’s heat as it shines through the south-facing windows and doors.

The walls and roof are assembled from structurally insulated panels (SIPs). These factory-cut custom panels feature continuous foam insulation sandwiched between two OSB boards. This eliminates the thermal bridging which causes cold spots where studs are located when conventional framing practices are employed. The walls were made from 6″ thick SIPs, and the roof was made from 10″ thick SIPs. The house is oriented with the front facing south, both to maximize passive solar gain and to present a south-angled roof on which to mount the solar panels.

All of the windows are triple-paned low-E glass. The porch roof angle allows the sun to enter the house in the winter but blocks the higher-angled sun during the summer months. There is also a green house off of the kitchen portion of the porch.

The primary heat source during non-sunny periods is an electric “mini-split” heat pump. These remarkably efficient units will keep a home of this size comfortably warm during the winter months for a fraction of the typical heating costs of the average house. The monthly total electric bills for this electrically heated house range from $9 to $30.

The head unit of the heat pump is positioned so that warm air is directed toward the concrete floor, storing the heat and warming the floor.

Fresh air exchange can be a challenge in tightly sealed homes such as this. Many modern homes solve this with expensive and power-consumptive heat exchange ventilation systems. As an alternative, this home employs a very simple, but effective, solution. Incoming air passes through “earth tubes,” which pre-warm the air in the winter and pre-cool it in the summer.

The appliances are smaller in size and very efficient. The slightly smaller appliances allow room for more counter space. The counters are stained concrete, molded on site, a considerable cost savings. The hot water system is a tankless, on demand unit.

Perhaps the most unique feature of this home is the feeling the internal space instills. There are only two internal doors. They are on the bathroom and a small downstairs bedroom. The rest is one open living space, but wherever one stands it feels like a separate room, and it always feels spacious. The layout was tailored to meet the needs of two people without children, but with only minor changes it could comfortably be converted to two bedrooms and two bathrooms.

An Award-Winning Home

The U.S. Department of Energy, which awarded TC Legend a Housing Innovation Award for this home, also created an excellent case study. Here are some highlights:

Energy-Efficient Plan Designed by TC Legend Homes

The Bellingham home achieves this performance with a simple plan designed by Clifton to maximize efficiency and minimize cost, with an open two-story layout including a small 630-ft2 footprint and a 400-ft2 loft. The home was placed on the lot to maximize passive solar heat gain and avoid shading the PV system, while retaining existing trees.

Attention to Detail Gets Results

Attention to detail helps Clifton achieve a very airtight envelope that shows air leakage of only 0.67 air changes per hour at 50 Pascals pressure difference (ACH 50) when tested with a blower door. . . . “Normally the insulation contractors spend about 2 hours air sealing. We spend 20 hours or more on a house, depending on the size of the house. It’s a line item in the budget. We may spend $2,000 on air sealing because we caulk everything,” said Clifton.

A Home That Practically Heats Itself

One high-efficiency ductless mini-split heat pump provides [heat]. . . . Despite the high efficiency of the unit, it rarely runs according to the homeowners, because the building shell is so well insulated.

Designed to Power a House and Car with Solar

The home’s standing seam metal roof simplified installation of the 3.2-kW grid-tied PV system. The homeowners Kristina and Mike Heintz were so interested in the installation of the solar panels that Kristina took on the task of locating the best solar value possible and ordering the panels. She has since joined TC Legend’s staff to handle solar panel purchases for other clients. . . .Clifton noted that while the 3.2-kW system meets all the home’s power needs, there is room on the roof to add enough PV to power an electric car as well.

Key Features

  • Walls: 6 in. SIPs R-26; pre-finished fiber cement siding; house wrap

  • Roof: 10 in. SIPs R-42; metal standing seam roof

  • Foundation: ICF foundation R-28; R-20 rigid high-density EPS foam board under slab

  • Windows: Triple-paned vinyl-frame, U=0.20, SHGC=0.45

  • Air Sealing: 0.67 ACH 50

  • Ventilation: 30 cfm, 2.7-Watt continuous exhaust fan in bathroom balanced by earth tube that brings in filtered, tempered outside air passively via 100-ft, 6-inch-diameter pipe buried 2 feet below ground inside foundation footing. Spot ventilation fans in kitchen and utility closet

  • HVAC: One ductless heat pump 12 HSPF, 21.5 SEER

  • Hot Water: Instant tankless condensing gas-fired water heater; 0.96 EF

  • Lighting: 100% LED for all fixed lights, 100% CFL for lamps

  • Appliances: High-efficiency electric washer-dryer combo

  • Solar: 3.2-kW PV

  • Water Conservation: Low-flow faucets, shower head

  • Other Low- to no-VOC glues, adhesives, and paints; water-based sealer on concrete floors

Greenlake Net-Zero-Energy Remodel

Greenlake Net-Zero-Energy Remodel

This net-zero-energy house remodel in Green Lake is designed to be budget-conscious, energy-efficient, and surrounded by lush gardens. It is a great example of an affordable deep-green remodel. Collaboration between owner, architect, and builder has created a beautiful synthesis of resource efficiency, connection to nature, and renewable energy — mixed together with a funky modern/industrial aesthetic.

The inspiration

The Northwest Green Home Tour inspired the owner Becky to learn all she could about green building. She joined the NW Eco Building Guild and attended green workshops.  She was particularly inspired by a net-zero energy home in Ballard. Wanting to “do it all” — renewable energy, rainwater harvesting, salvaged materials, and much more — she dove in and spoke with many green professionals in the Guild.

Team approach

    1. The owner

      Becky started with a desire to go “super green” while being cost-effective, and she had lots of great design ideas. After finding a well-located home with good solar orientation and a solid structure (although in need of an aesthetic update), she pulled together the project team of LD Arch Design and TC Legend Homes, as described on her blog about the project.

      The design goals

      The existing home was in serious need of aesthetic and energy updates, with an interior so carved up it felt like every room was small and dark. The goals for the remodeled home were:

      • Create a high-efficiency, net-zero-energy house
      • Raise the roof to provide a good spot for solar and let light in
      • Connect to the garden and integrate rainwater harvesting
      • Use some of the unfinished basement/garage space for bedrooms
      • Have an open floor plan at the upper level that would be good for entertaining
      • Create a more modern and industrial aesthetic
      • Demonstrate that high-quality green design can be affordable

      Green choices 

        1. Less energy

          • Renewable energy: Budgeting to include solar panels was a priority.
            • 6.72kW solar module sized to meet and exceed energy usage
            • Plan for future electric car charging station
          • An energy-efficient building envelope: The envelope performs well above energy code.
            • 6” SIPS panel walls and 9.5” SIPS panel roof
            • 4” rigid insulation installed over existing concrete slab
            • Triple-pane high-quality vinyl windows
          • Energy-efficient equipment and lighting: The mechanical systems, appliances, and lighting are selected to be highly efficient.
            • Mini-split ductless heat pump
            • Heat pump water heater
            • EnergyStar bath fans, refrigerator, and dishwasher
            • High-efficiency horizontal axis washing machine 
            • LED light bulbs
          • Air sealing: Heat loss through air leaks can be virtually eliminated with modern building technologies.
            • SIPS panels provide a sealed wall system
            • Careful air sealing at openings and penetrations
            • Whole-house ventilation system to ensure adequate fresh air

            2. Less new stuff

              • Reuse and deconstruction: Materials are treated carefully rather than being sent to a landfill.
                • Much of the home’s structure is reused
                • Existing materials deconstructed and used elsewhere in the house
                • A new use found for almost everything removed from the house
                • Construction waste reduced by precise materials ordering
              • Reclaimed and recycled content materials: Becky combed salvage shops for materials that fit the desired aesthetic.
                • Salvaged stainless steel counter and sink in kitchen
                • Light fixtures made with salvaged material
                • Salvaged wood trim
                • Recycled content fiber cement board siding and gypsum wall board

                3. Less toxic stuff

                  • Nontoxic materials: A priority is placed on selecting materials that do not outgas toxic fumes.
                    • Wood products with no added urea formaldehyde
                    • Nontoxic caulks and adhesives
                    • No-VOC paints and finishes
                    • Marmoleum natural linoleum flooring
                  • Hard-surface flooring: A carpet-free home reduces dust and allergens. The home is a “shoes-off” home to avoid tracking in pollution.
                  • Healthy ventilation design: This is particularly important in a house with an airtight envelope.
                    • High clerestory windows open to draw fresh air up and through the home
                    • HVAC system with HEPA filter includes a fresh air supply

                    4. Less water

                      • Efficient plumbing fixtures
                        • Dual flush toilet with integral hand washing sink
                        • Efficient horizontal axis washing machine
                        • Low-flow shower and faucet aerators
                      • Water efficient site design
                        • Rain cisterns and barrels to capture and store water for landscape watering
                        • Native and drought-tolerant landscaping
                        • Master Composter in residence
                        • Design to celebrate the flow of water in our rain-rich environment

                      Photos by Holli with an i Photography unless noted otherwise.