BrightLeaf Homes built this duplex of two side-by-side 2,280-square-foot custom homes in La Grange, Illinois, to the high performance criteria of the U.S. Department of Energy Zero Energy Ready Home (ZERH) program.

The exterior walls of the homes use a staggered stud wall system consisting of 2-by-4 studs set every 12 inches on 2-by-6 top and bottom plates and staggered so that each alternating stud aligns with either the inside or outside edge of the plates. Insulation is woven between the studs to provide a continuous thermal break in the wall cavity.

The low-cost, foam-insulated, vinyl-framed, triple-pane windows are argon filled with low-e coatings and provide low air infiltration and high u-factors of 0.22 to 0.18. The window sizes are standardized to the stud spacing as much as possible to minimize measurement mistakes and reduce the amount of studs used around the windows. A piece of beveled cedar is installed on each window sill under the flashing to create a positive slope away from the interior of the house.

The simple gable roof is constructed at an unusual 6.55 pitch that allows exactly four and a half sheets of 4-foot-wide coated, taped roof sheathing to be installed as the roof deck with enough space at the peak for a continuous ridge vent. ENERGY STAR reflective shingles cover the roof, which is ideally angled for solar panels.

All of the home’s faucets and plumbing fixtures are WaterSense labeled and the dishwasher and refrigerator are ENERGY STAR-rated, adding to water and energy savings.

All of the home’s light fixtures are equipped with LED bulbs, including the four ENERGY STAR-rated ceiling fans.

The basement walls are wrapped with 3 inches of XPS rigid foam that will be taped at the seams then covered with a dimpled plastic water barrier. The basement walls extend 3 feet above grade providing basement rooms with daylight through 24-inch-tall above-grade windows.

A coated OSB sheathing product covers the walls. When the seams are taped, the sheathing serves as a weather-resistant barrier as well as an air barrier so no house wrap is needed.

Domestic hot water is provided with a sealed-combustion natural-gas-fired tankless hot water heater with an energy factor of 0.97. A single plumbing wall on the second floor that serves both bathrooms and the second-floor laundry room, which limits the distance that any hot water needs to travel and all hot water lines are completely insulated.

The walls are filled with R-26 of blown cellulose. The raised heel energy trusses are spray foamed to seal the baffles, which will provide a ventilation path to the soffit vents. Interior top plates will also be spray foamed before 16 inches (R-60) of cellulose is blown over the attic floor.