TC Legend Homes built this 2,707-square-foot custom home in Bellingham, Washington, to the high performance criteria of the U.S. Department of Energy Zero Energy Ready Home (ZERH) program.

With the 10-kW of solar panels installed on the roof, the super-efficient home is expected to have utility bills of about $90 per year.

Overhangs block high summer sun but let in lower winter sun for beneficial heating. Durable fiber cement plank siding and cedar details cover the SIP home.

Large south-facing windows allow any available sunlight in to warm the stained concrete flooring. The concrete slab warms up during the day and radiates heat through the night providing passive heating.

ENERGY STAR appliances and LED lighting add to energy savings.

The air-to-water heat pump efficiently heats water for space heating and hot water at the tap.

The walls and roofs are made of graphite-enhanced SIPs. The wall panels are 6.5-inch SIPs and the roof panels are 10.25-inch SIPs. The panels come to the site pre-cut for quick assembly. A double bead of caulk helps ensure airtight seams. The joints will also be taped.

These Washington-made SIP panels use a polystyrene foam that has graphite added for improved insulating abilities. Unlike some SIP installations that use solid wood splines to connect the panels, TC Legend uses a specially designed spline that combines foam and wood to provide insulation at the panel joints, which are taped to increase air-sealing. Rim joists are spray foamed.

The 10 kW of solar panels on the roof help the home achieve a HERS Index score of -11, meaning that it produces a bit more electricity than it uses over the course of a year. In fact, it makes enough to power both the house and an electric car.

The home's super-efficient (COP 3.92) air-to-water heat pump provides radiant floor heat to the downstairs and hot water to a fan coil for the second floor as well as domestic hot water for the house. The ducts are for the heat recovery ventilator, which runs continuously to bring filtered fresh air into the home.