Breathing Space

‘Today’s New Living Experience at Walnut Farm’ places indoor air quality at the forefront of the ‘simplicity of the build.’

Content courtesy of the U.S. Department of Energy. Edited by Green Builder staff.

For veteran home builder Jay Epstein, a lifetime of construction experience can be distilled into one phrase: the “simplicity of the build.” For Epstein, this philosophy means combining standard construction and quality installation with better materials and a few new technologies, added only where they make sense from a cost or performance perspective.

It’s been a winning combination for Epstein, who recently crowned his 44-year career in the home building industry by earning a grand award in the “Off the Shelf” category in the U.S. Department of Energy (DOE)’s 2023 Housing Innovation Awards (HIA) competition. The award honored his project, “Today’s New Living Experience at Walnut Farm.”

The “Today’s New Living Experience at Walnut Farm” home was so carefully crafted, it received a HERS Index score of 8—about 10 times better than a built-to-code, comparably sized new home.

As Epstein prepares to hand over the reins of his Healthy Communities construction company in Williamsburg, Va., to his daughter, Morgan Epstein Wojciechowski, he reflects back on a career that’s seen the construction and certification of more than 95 homes to the DOE Zero Energy Ready Home (ZERH) criteria, with 90 more currently in the pipeline.

For Epstein, simplicity of the build means designing energy-efficient homes that contractors can easily put together without requiring a lot of new skills.

For example, Epstein uses site-built stick-frame construction or factory-made exterior wall panels. But instead of 2-by-4 16-inch on-center, Epstein specifies 2-by-6 24-inch on-center framing with simple advanced framing adjustments such as turned three-stud corners, insulated headers, and ladder blocking at intersecting walls so the walls can hold more insulation while using less lumber. 

Instead of wrapping the sheathing with house wrap, Epstein specifies 0.625-inch R-3 graphite-enhanced expanded polystyrene (GPS) rigid foam. “It’s lightweight; it does not need to be structural due to the 0.5-inch plywood it’s attached to,” he says. “Nine cap nails can hold a 4-by-8 sheet, and we can nail the fiber cement siding right through to the studs.” 

With seams taped, the rigid foam serves triple-duty as a weather-resistant barrier, drainage plane, and thermal break to stop heat transfer through the studs. “We are not really doing anything special,” Epstein notes. “It’s not rocket science. We’re back to the basics, just with better tools.” 

Buyer Benefits

Epstein’s winning philosophy has also paid off for the homeowners. When Epstein had the award-winning home performance tested and modeled by an energy rater, it achieved a Home Energy Rating System (HERS) Index of 8. A typical new home would score around 80; a net zero energy home—one that produces as much energy as it consumes in a year—would score a 0. The owners of this home told Epstein they have yet to pay anything for power beyond the utility’s $6 monthly demand charge.

According to Epstein, energy independence is perhaps the most notable advantage of zero energy homes—their ability to free homeowners from the uncertainties of rising energy costs.

“With renewable energy sources onsite, homeowners can significantly reduce or even eliminate their reliance on the grid, resulting in considerable energy savings,” he says. The owners of Today’s New Living Experience at Walnut Farm will have calculated annual energy savings of $2,650 per year compared to the same home just built to code. They’ll also get the added benefits of improved comfort and better indoor air quality.

Every DOE ZERH is also certified to the criteria of ENERGY STAR Certified Homes Version 3.1 or 3.2 and the U.S. Environmental Protection Agency (EPA)’s Indoor airPLUS program.

Builders must also meet other efficiency requirements such as the hot water distribution requirements of the EPA’s WaterSense program; the insulation requirements of the 2015 International Energy Conservation Code; HVAC and water heating efficiencies; third-party verified air sealing targets; installation of ENERGY STAR appliances, windows, and lighting; and ducts in conditioned space. In addition, homes are required to have photovoltaic (PV) panels installed or have the conduit and electrical panel space in place for future installation.

Construction ABCs

This home is on a lot at Walnut Farms where the builder has already constructed 58 of a planned 75 DOE Zero Energy Ready certified homes.

These semi-custom homes start with wall panels that are constructed in clean, dry conditions in a factory, then shipped to the site, along with open-web floor joists and engineered roof trusses, for quick assembly, allowing the shell to be constructed in just three days and ready for windows, doors, shingles and siding. “This panelized approach enables us to maintain control over pricing and material waste,” Epstein says.

The wall panels are insulated onsite with a flash-and-batt approach that includes spraying 1 inch of closed-cell foam into the wall cavities to seal the sheathing to the framing, then filling the remainder of the wall cavities with blown cellulose or fiberglass batt.

The exterior is wrapped with a 0.625-inch R-3 layer of graphite-enhanced expanded polystyrene (GPS) that stops thermal bridging through the walls via the studs and brings the walls’ total insulation value to R-24. 

The seams of the rigid foam are taped so it can serve as the weather-resistant barrier and drainage plane for the above-grade walls. The below-grade walls of the conditioned crawlspace are insulated along the interior with an R-10 layer of GPS, and the rim band is filled with 5.5 inches (R-19.5) of open-cell spray foam. The interior level of the crawlspace floor is higher than the exterior grade around the home, so no perimeter foundation drainpipe is needed.

Before filling the attic with R-49 of blown cellulose insulation, all top plates were sealed from the attic with 2 inches of open-cell spray foam. The attic access hatch was insulated and sealed with a gasket. The 24-inch on-center trusses of the gable roof align with the wall studs and included 14-inch raised-heel trusses to allow space over the exterior wall top plates for the full depth of attic insulation.

The truss design was strengthened from 10 pounds to 15 pounds per square foot to accommodate the solar installation. A unique “storage cradle” or platform was designed into the trusses to provide desirable storage space that is elevated from the attic floor enough to allow a full R-49 of insulation underneath.

ENERGY STAR-rated double-pane windows with low-emissivity coatings complete the highly efficient building envelope. The windows have an insulation U-factor of 0.28 and a solar heat gain coefficient of 0.22.

Epstein worked with the local window manufacturer who made several design changes to improve air tightness after visiting Healthy Communities’ homes during blower door testing to see the impact leaky windows can have on a home’s overall air tightness.

Energy Star-rated appliances, a highly efficient heat pump water heater, and a push-button controlled recirculation pump on the hot water distribution system contribute to hot water and energy savings. The recirculation pump alone is estimated to save 9,125 gallons a year in water at an estimated homeowner savings of $130 per year.

With all of the air sealing measures implemented, Epstein’s homes are able to achieve an air tightness of 1.94 air changes per hour at 50 Pascals pressure differential (ACH50), within the 2.5 ACH 50 needed to meet the program specifications for his climate zone.

Keeping Minds on the Work

“Employing a common-sense approach and taking the time to do it correctly makes the ‘simplicity of the build’ easier,” Epstein says. “Collaborating with your insulation installer to complete the wall system seal is critical. It is also crucial to work closely with your third-party rater, as they are there to assist you in building a superior home rather than just to find problems.”

Indoor air quality is a critical element for Epstein, who first became interested in home building when he was looking for a healthier home for his daughter, who had asthma. To ensure good air quality in well-sealed homes, Epstein installs an energy recovery ventilator that brings in fresh filtered air and tempers it with outgoing conditioned air via a heat exchanger that transfers heat and humidity to reduce the amount of humidity brought into the home.

The incoming air passes through a MERV 8 or MERV 13 filter and is distributed throughout the home via the central air handler’s supply ducts. A central return draws stale air from the home. 

This home’s heat pump system was also equipped with an air cleaner that can remove 99.98 percent of allergens from the air. 

The ERV and HVAC can be remotely operated via an app. For spot ventilation, the bathrooms are equipped with Energy Star quiet exhaust fans that have humidity sensors to increase fan speed during and after showers.

A central heat pump provides space heating with an efficiency of 9.6 HSPF and cooling with an efficiency of 18 SEER. The unit has a variable-speed air handler and multistage compressor that uses a network of sensors to monitor and optimize humidity and temperature in the home, adjusting compressor and fan speeds in real time to provide consistent temperature with maximum efficiency. 

The multistage system can adjust output to operate from 0.75 tons to 2 tons as needed. The system automatically adjusts the indoor unit’s fan speed at startup to draw more moisture from the air for better humidity control. All of the ducts are mastic sealed, insulated to R-8, and located in the insulated conditioned crawl space.

Homeowners could save an estimated $2,650 in annual utility bills thanks to a highly effective building envelope, and 6.32 kilowatts of solar panels.

According to Epstein, one key to efficient HVAC performance is proper equipment sizing. Many HVAC contractors “still use old rules of thumb and end up oversizing equipment.” Epstein has his energy rater perform heating and cooling load calculations to determine equipment sizing in accordance with the industry standard, Manual J. 

Healthy Communities also uses a compact duct layout following Manual D, both from the Air Conditioning Contractors of America (ACCA).