Lynden Powerhouse

Lynden Powerhouse

Lynden Powerhouse

Lynden Powerhouse is a highly efficient, net-positive home with an additional ADU and stick-framed garage/shop. This home will receive the DOE Zero Energy Ready Home, ENERGY STAR, and EPA Indoor airPLUS certifications, and anticipated Built Green 5-star certification.

Lynden Powerhouse will provide full-time and temporary housing for up to four separate family groups. This level of complexity required a greater attention to climate and ventilation zoning, which necessitated the installation of three separate Fantech Hero 250 HRV units and one extra-large Chiltrix CX50 heat pump. These devices allowed the home to be compartmentalized into three separately conditioned spaces – the main living space downstairs, living space upstairs, and ADU. Breaking up the air spaces ensures that the fresh air circulation can independently adapt to the measured CO2 levels and temperatures of each air volume. Given that hazardous airborne viruses are a normal part of life for the foreseeable future, having three separated air spaces allows those infected to quarantine without infecting others. Further measures to make the home as energy efficient as possible with the best indoor air quality included hydronic radiant floor heating, HRVs with integrated HEPA filtration, all ENERGY STAR rated appliances, LED lighting, triple pane windows, and Aerobarrier air sealing.

One of the owners, who works in the tech industry, used his knowledge to create innovative automation systems for the ventilation and hot water circulation systems using motion detectors and CO2 sensors to minimize wasted energy, water, and time. Each air space has a motion sensor that will stop the HRV unit if no motion is detected for 24hrs to conserve energy. Additional automation uses custom algorithms to vary the HRV air velocity to balance CO2 extraction with ventilation-induced heat energy loss. Motion sensors placed near each plumbing fixture trigger the hot water circulators only when need is anticipated. By the time the person turns on the fixture, hot water is available, minimizing both water, time, and energy waste.

Lynden Powerhouse features a 17.01 kW solar array with six 48v 100AH LFP batteries for backup storage. The system was designed to be oversized, knowing that the combination of PV with storage allows for disaster resiliency and for the house to operate completely off-grid for weeks if needed. It also supports three EV charging ports, two for occupants and one outside for guests. Moreover, having an oversized solar array on an already super-efficient house, means the owner can eliminate the entire energy bill which makes retirement budgeting more predictable and effectively making the cost of living cheaper in the future. By over-sizing the system, the house can fully power the AC units of four less efficient homes in the cul-de-sac, thereby minimizing peak energy loads for the entire block. The reduction in peak-energy loads helps reduce the stress on the grid caused by extreme weather events. And is the key to eliminating petroleum powered peaker plants, thereby reducing CO2 production for the entire street.




  • Overview:

    • 1549sf SFR &  842sf ADU
    • 1123sf unconditioned garage & shop
    • 4 bedroom, 3.5 bath SFR &  1 bedroom, 1 bath ADU
    • Net Zero Energy
    • 1st floor aging-in-place
    • Passive solar heating/cooling design
    • Insulation: R-29 walls & R-59 ceiling
    • Air Sealing: 0.45ACH
    • HERS Index: -24
    • Annual Energy Cost Savings: $3,717
    • Certifications: DOE Zero Energy Ready Home certified, ENERGY STAR certified, EPA Indoor airPLUS certified, anticipated Built Green 5-star certified



    • Ventilation: (3) Fantech Hero 250 with built in HEPA filter. Built-in humidity, temperature, and CO2
    • Heating/Cooling: Chilltrix CX-50; hydronic radiant floor heating downstairs and (3) fan coil units
    • PV: 17.01kW solar array with whole home battery back-up



    • Timber framed entry
    • Metal roof
    • Locally made walnut and maple cabinets
    • Bamboo Floor Score certified flooring
    • Vanair vented interior doors
    • Locally made solid fir front door
    • Silestone and Corian countertops
    • ENERGYSTAR appliances
    • LED lighting
    • WaterSense plumbing fixtures
    • No/Low-VOC finishes
    • Triple pane, Low-E coated, argon-filled vinyl windows
      Victory Heights Net-Zero Home

      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.

      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).

      Toomes’ Bellingham Affordable Net-Positive Home

      Toomes’ Bellingham Affordable Net-Positive Home

      Built by the TC Legend Homes/Powerhouse Designs team. We design and build. With a standard palette of materials & details that have been chosen, tested & refined over many houses, there is no confusion for the crew. The draftsman, engineer, and crew are consistent through all our projects, so everyone has done this system before.

      Key Features:

      • Positive Energy – produces enough electricity to also power an electric car.

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

      • Honorable Mention in the Affordable Category of the 2018 US Department of Energy Housing Innovation Awards.

      • The home is oriented for both passive & active solar performance by facing south, as a rectangle with the long side (26’) running from east to west. The home is outfitted with an 8.1kw photovoltaic system.

      • Energy envelope includes structural insulated panels (SIPs). The 6.5″ Neopor R29 SIPs panel walls are locally made in Washington. Designed & engineered to reduce cold bridging by minimizing structural lumber & maximizing use of foam splines to connect panels. Shell is air sealed with triple beads of mastic at all joints and panels additionally taped at all joints. RIM joist insulated with R30 spray-foam at floor systems. Perfect rectangle box adds simplicity to construction & reduces corners & thus cost & air leakage.

      • 4″ Extruded Polystyrene (EPS), a low VOC foam (R20), is used under-slab. The concrete slab-on-grade is exposed and is effectively a free finished-floor and a functioning thermal mass.

      • The heat recovery ventilator (HRV) is a Zehnder Comfo-air 200 which can scavenge 95% of the heat from the outgoing dirty air. Running through a class 4 filter (merv7/8) at between 29 and 118 cubic feet/ minute (cfm), the unit ventilates the whole house, extracting moist air from bathrooms/utility spaces, bringing fresh air into living spaces.

      • Energy Star appliances including a Geospring 50-gallon heat pump-powered hot water heater.

      • Stormwater from the roofs is infiltrated on-site using splash blocks below the gutter downspouts.

      • Home Energy Rating System (HERS) Index is negative 25!  (A typical new home has a rating of + 62.)

      Ballard Net-Zero-Energy Home

      Ballard Net-Zero-Energy Home

      Owners: Eric Thomas and Alexandra Salmon

      Designer: Zero-Energy Plans, LLC (

      Builder: TC Legend Homes (

      Site Address: 612 NW 60th St., Seattle, WA 98107 (Ballard)


      1,915 square feet, single-family, 2 stories, 3 bedrooms + work loft, 2 bathrooms, concrete slab foundation, radiant heat floors, Hardie plank siding.


      Structural Insulated Panel construction, air-to-water heat pump, 6kw solar electric (photovoltaic) system, triple-pane windows, passive solar design, rain garden, stained concrete floors, reclaimed fir floors, recycled fixtures, zero-VOC paint, low-waste engineering, low-energy LED and CFL lighting, capacity for additional solar panels to power an electric car 5,000 miles per year.