Read Our 2016 Housing Innovation Award-Winner Case Study
TC Legend Homes built this 2,463-ft2 home in Seattle, Washington, to the performance criteria of the DOE Zero Energy Ready Home (ZERH) program. The two-story home has SIP walls and triple-pane windows for draft-free construction and high insulation values.
- Name: 19th Avenue
- Location: Seattle, WA
- Layout: 4 bdrm, 2.5 bath, 2 fl, 2,463 ft2
- Climate Zone: IECC 4C, marine
- Completion: May 2016
- Category: custom for buyer
Modeled Performance Data
- HERS Index: without PV 44, with PV -2
- Projected Annual Energy Costs: without PV $1,053, with PV $25
- Projected Annual Energy Cost Savings (vs home built to 2012 IECC): without PV $811, with PV $1,889
- Projected Annual Energy Savings: without PV 9,453 kWh, with PV 20,993 kWh
- Added Construction Cost: without PV $0
When a net-zero-energy home can be built at a cost on par with traditional construction, everyone wins. TC Legend Homes is helping to usher in a new era of green construction in which home owners don’t have to choose between cutting-edge efficiency and staying on budget.
“Over the last decade, we’ve developed practices that allow us to build net-zeroenergy homes for the same price as traditionally constructed homes. Sometimes,
we are able to build them for even less,” said TC Legend Homes’ owner and lead Ted W. Clifton, Jr.
“We know we are doing something right because our services are in high demand,” said Clifton, who is headquartered in Bellingham, Washington, but also builds in the Seattle area.
One way TC Legend Homes is achieving net zero is by building to the high performance criteria of the U.S. Department of Energy’s Zero Energy Ready Home program. DOE has honored the builder with four Housing Innovation Awards since 2013, including a grand award in 2014 in the affordable category
and a 2016 award in the custom home category. The 2016 award-winner is a two-story, 2,463-ft² home located next to another TC Legend Home on an urban
infill lot in Seattle.
The high-performance features of this home, combined with the 9.5-kW PV system
and solar water heating, help the home achieve a Home Energy Rating System
(HERS) score of minus 2. That equates to calculated annual utility costs of $25
(counting service charges) or enough electricity to power the all-electric home. If
the home performs better than calculated, it will cover the power for the electric
car charging station in the garage as well. Even without the PV, the home would
achieve a HERS score of 44, far better than the HERS 80 to 100 of typical homes.
Clifton is used to getting such scores. He has been certifying homes to the DOE
Zero Energy Ready Home program since 2013. His previous winning homes have
HERS scores ranging from -12 to 13 with PV or 34 to 43 without PV. Clifton has
committed to building all of his future homes to the program.
The DOE Zero Energy Ready Home program requires homes to meet all of the
requirements of ENERGY STAR Certified Homes Version 3.0 and the U.S.
Environmental Protection Agency’s Indoor airPLUS program as well as the
hot water distribution requirements of the EPA’s WaterSense program and the
insulation requirements of the 2012 International Energy Conservation Code.
In addition, homes are required to have solar electric panels installed or have
the conduit and electrical panel space in place for future photovoltaic panel
The 2016 award-winning home was situated on the northern edge of the lot to maximize southern exposure. “Our houses are designed from the ground up to take advantage of the sun. A passive solar layout like the one in this house means lots of windows facing south and few facing north,” said Clifton. The long axis of the house is east to west to allow for maximized solar exposure for the PV and solar hot water systems and for passive solar heating. High-quality triple-paned, vinyl-framed windows were located on the south side of the house to maximize
solar heat gain. The builder polishes and stains the concrete floor slab to use as the finished flooring; its thermal mass absorbs heat from the sun during the day and slowly releases it at night to provide beneficial passive solar heating.
Structural insulated panels (SIPs) were used for the walls and roofs. “We chose SIPs for their excellent insulation values, airtightness, and ease of construction,” said Clifton. SIPs consist of two layers of OSB sandwiching a layer of rigid expanded polystyrene foam. They arrive from the factory as 4×8-foot sheets or precut for doors and windows as required for each wall. Clifton uses locally made panels that come precisely cut, allowing for fast construction, a strong, airtight
shell, and practically zero jobsite waste. The TC Legend Homes crew is trained in
SIPs construction, which helps assembly go smoothly. Clifton has used SIPs ever
since he began constructing homes with his father, Whidbey Island builder and
designer Ted L. Clifton, while in high school. Ted Clifton Jr. is on site daily to
oversee every step of the TC Legend home construction process, allowing for any
problems to be quickly fixed.
For the winning home’s walls, Clifton specified R-29, 6-inch SIPs that are glued
and taped at all interior and exterior joints. The panels are covered with house
wrap that is overlapped and taped to serve as a drainage plane under the fiber
cement siding. The roof decking consists of R-42, 10-inch SIPs, also taped at all
interior and exterior joints. The whole roof deck is covered with self-adhering
ice-and-water shield, which provides a weather-resistant layer under the asphalt
shingles. There is no attic in the home. Because the SIP panels provide the
insulation and roof decking in one layer, all of the home’s upper-floor rooms
can have vaulted ceilings.
The home has a slab-on-grade foundation with stem walls made of insulated
concrete forms (ICFs) that wrap the sides of the slab in R-23 of insulation while
an R-20 layer of rigid foam covers the ground under the entire slab. Seams are
taped and the rigid foam layer serves as the vapor barrier between the ground and
The concrete floor slab contains radiant floor loops. Water for the radiant floor
heating is provided by the roof-mounted evacuated tube solar hot water system
and by an ultra-efficient air-to-water heat pump with a coefficient of performance
(COP) of 4.5. These systems also provide domestic hot water. The heat pump’s
indoor unit is centrally located on the main floor. Low-flow fixtures help cut
ENERGY STAR-rated appliances also reduce water and energy usage. All of the
home’s lighting is provided by LEDs, adding to energy savings.
The home was assessed by a home energy rater per DOE Zero Energy Ready
Home requirements and showed air leakage of only 0.60 air changes per hour
at 50 Pascals. That’s equivalent to the Passive House Institute U.S. Standards
and three times tighter than required by the newest energy code. (The 2015
International Energy Conservation Code requires 3 ACH 50 or less.)
To provide good ventilation for the home, the builder installed timered exhaust
fans to provide spot ventilation in the four-bedroom home’s 2.5 bathrooms. The
range hood fan is timer controlled with a 200-cfm fan that pulls fresh air into the
home through a vent located downstairs on the north side of the home. Both fans
can be set to come on for balanced ventilation during the day and for night-time
cooling in the summer.
Use of low- and no-VOC paints, finishes, and flooring and good moisture
management practices like site grading and drainage were among the measures
the builder installed to comply with the requirements of the EPA’s Indoor
- DOE Zero Energy Ready Home Program, 100% commitment
- ENERGY STAR Certified Homes Version 3.1
- EPA Indoor airPLUS
In a “green” market like the Pacific Northwest, marketing DOE Zero Energy
Ready Homes is easy. TC Legends has found it gets more than enough
customers through these avenues: 1) referrals from other customers; 2) TC
Legends’ website; 3) TC Legends’ presence on other websites, for example the
DOE Tour of Zero and Housing Innovation Awards sites; and 4) participation
in the annual Northwest EcoBuilding Guild’s Green Home Tour.
“Because TC Legend Homes builds custom homes, most of our potential
customers approach us already wanting an energy-efficient home. We educate our
customers about how our homes are different from most houses and about how we
achieve net-zero energy and positive energy in the homes we build,” said Clifton.
“By conserving as much energy as possible, these homes will be able to offset
more than 100% of their electricity usage with the roof-sized solar electric
systems.” said Clifton.
By value engineering and fine-tuning their processes, TC Legends is able to achieve zero energy at surprisingly low cost. “We only do net zero energy construction, and for less than most builders in the area do regular construction. We average $200/ft² including solar,” said Clifton.
- DOE Zero Energy Ready Home Path: Performance.
- Walls: R-29, 6″ SIP taped at all interior and exterior joints, fiber cement siding.
- Roof: R-42, 10″ SIP taped at all interior and exterior joints. Ice-and-water shield, asphalt shingles.
- Attic: None.
- Foundation: R-23 ICF stem walls, R-20 rigid foam under slab.
- Windows: Triple-pane, vinyl-framed, low-e windows, U=0.21.
- Air Sealing: 0.60 ACH 50.
- Ventilation: Timered exhaust fans.
- HVAC: Evacuated tube solar hot water and 4.5 COP air-to-water heat pump for in-floor radiant hydronic heat.
- Hot Water: Air-to-water heat pump, COP 4.5.
- Lighting: 100% LED.
- Appliances: ENERGY STAR refrigerator, clothes washer, range hood; induction cooktop.
- Solar: 9.5-kW PV, evacuated tube solar hot water.
- Water Conservation: Low-flow fixtures; centrally located water heater.
- Other: Low-VOC paints and finishes.
- Electric vehicle charging stati
The U.S. Department of Energy invites home builders across the country to meet the extraordinary levels of excellence and quality specified in DOE’s Zero Energy Ready Home program (formerly known as Challenge Home). Every DOE Zero Energy Ready Home starts with ENERGY STAR Certified Homes Version 3.0 for an energy-efficient home built on a solid foundation of building science research. Advanced technologies are designed in to give you superior construction, durability, and comfort; healthy indoor air; high-performance HVAC, lighting, and appliances; and solar-ready components for low or no utility bills in a quality home that will last for generations to come.
For more information on the DOE Zero Energy Ready Home program
go to https://energy.gov/eere/buildings/zero-energy-ready-home
Download the case study in PDF.