On the Rise

When there’s not enough room to build a home outside, think up—way up.

Todd Usher, president of Addison Homes in Greenville, South Carolina, considers himself a semi-custom home builder, offering his home buyers a curated suite of house plans, interior, and exterior finish options.

However, for the benefit of his customers, there is one standard upgrade on his homes: Each one is constructed to the high-performance criteria of the U.S. Department of Energy (DOE)’s Zero Energy Ready Home (ZERH) program.

The energy-efficient Westbrooke Infill by Addison Homes was based on a narrow floorplan with two full stories, a partial third floor to house a fourth bedroom, bath and playroom, and a basement with the garage, mechanicals, rec room, and storage.

Usher is unique in focusing on DOE ZERH construction. Addison Homes completed its—and one of South Carolina’s—first such home in 2015. Addison is currently the only South Carolina builder certifying homes to the requirements of the program. It has constructed 11 homes to the ZERH standards, including six that have won DOE Housing Innovation Awards. In 2024, Addison was recognized with its second DOE Zero Energy Grand Award.

The four-level Westbrooke Infill home in Powdersville, S.C., is proof that DOE’s ZERH requirements may be a recipe. A recipe, yes, but no cookie cutter. This home is unique for Usher in terms of its layout and some of the technologies incorporated into the home.

The narrow, sloping, wedge-shaped lot was the last one available in a 30-year-old suburban neighborhood. The lot dimensions left little room to spread out, so Usher worked with the owners on a floorplan that instead went up, with two full stories plus a partial third floor to house the fourth bedroom, fourth bath, and playroom. A walk-out basement below contains the garage, mechanicals, rec room, and storage.

Inside information

While many past Addison homes had an insulated crawlspace, the sloped lot of this home was ideal for a daylight basement, providing more living space within its compact 38.5-by-25.6-foot footprint. Basement walls were constructed of pre-cast concrete panels engineered specifically for the home. The concrete walls have waterproofing on the exterior, while an integrated rigid foam layer wraps the inside surface of the walls and molded concrete studs. The foam-wrapped studs are faced with metal to provide an interior drywall nailing surface. 

The panels are made offsite in a factory in North Carolina and trucked to the home site, where they can be set in place with a crane in less than a day. “Construction can begin immediately and we don’t have to do anything other than run electrical through them and hang drywall,” says Usher. “For us, this is more cost effective than doing a poured concrete wall that then has to be cured, waterproofed, insulated and framed.”

The home’s stick-framed walls were constructed with several advanced framing
techniques, including 2-by-6 studs at 24-inches on-center spacing, two-stud (not three-stud) corners with drywall clips, open and insulated headers, and ladder blocking rather than solid blocking at interior wall intersections. All of these steps reduce the amount of lumber needed for framing while increasing the amount of space in the walls for insulation. 

The walls were packed with R-19 unfaced fiberglass batts, then sheathed with a coated OSB with a one-inch layer of polyisocyanurate foam glued to the inside surface. “This is the first home we built using a wall assembly construction of 2-by-6s at 24 inches on center and the R-6 coated sheathing,” says Usher. “Moving from R-13 cavity insulation to R-19 makes the house far more energy efficient, with thicker, quieter walls, and did not add significant overall cost.”

Usher credited the coated insulated sheathing with helping them achieve exceptional air tightness. “[The sheathing] did not require the special nails and tape of other exterior insulation products,” he says. “It saved us multiple labor steps since it includes sheathing, continuous insulation, and weather barrier in one product,” says Usher.

For the gable roof assembly, Usher used locally made engineered roof trusses and, as with previous homes, insulated along the underside of the attic with 8 inches of open-cell spray foam that covered all truss top chords, providing an attic insulation value of R-31 and an unvented conditioned attic space for ducting and living space.

Addison incorporated a “vapor vent” along the ridge of the roof by using a vapor-open house wrap beneath roof ridge venting to avoid potential condensation issues.

All seams in the OSB roof sheathing were taped per the Insurance Institute for Building and Home Safety (IBHS) Fortified Roof standard to increase the home’s hurricane resistance. The roof was topped with synthetic underlayment and asphalt architectural shingles.

“Offsite-manufactured components like roof trusses, floor trusses, and basement wall panels, and the accompanying engineering plans that specify the location for each component, are integral to our approach to quality construction, as they avoid framers having to make a lot of ad hoc decisions in the field,” Usher says. “They also reduce labor time and waste for cost savings.”

Environmental Aspects

The ventilation system for the home consists of fresh air intakes on the ventilating dehumidifier and exhaust fans (not balanced). The central thermostats control the HVAC setpoint for heating and cooling, a humidistat for control of the dehumidifiers, and ventilation control based on ASHRAE 62.2. The bath exhaust fans are controlled by a humidity sensor, a timer, and a manual switch. 

The range hood is wired to open the fresh air damper when the range hood is in use to provide makeup air, although this is not required by code or the DOE ERH standard. Space heating is provided by two high-efficiency (9.2 HSPF2, 18.7 SEER2) variable-speed heat pumps: 1.5 ton for the basement and main level, and 1 ton for the two upper floors. “That’s just 2.5 tons for all 3,682 square feet,” Usher says. 

Both systems were sized using ACCA Manual S based on a Manual J load calculation. Transfer grilles were used to balance air pressures between rooms and return ducts. Usher selected a compact duct system using 3-inch- and 4-inch-diameter uninsulated ducts that run through the floor cavities of the home. Each heat pump was paired with a ventilating dehumidifier to manage the latent load in the home and to provide fresh air ventilation.

“This is the first time we used thermostats with integrated controls for temperature, dehumidification, and ventilation of fresh air,” Usher notes. The thermostats are connected to the internet where the homeowner can control the home’s systems and monitor electrical usage of the whole house and individual circuits.

To get the desired HVAC performance, Usher has taken the unusual step of bringing all of his HVAC design in house. “We currently do the HVAC system design, procure the equipment and ductwork materials, then hire installers and provide them with step-by-step installation instructions,” says Usher.

Serving the Client

Usher, a recent PhD graduate and current professor in Clemson’s Department of Construction Science and Management, has put his educator skills to use—not just with subcontractors but also with college students, code officials and fellow builders.

Usher is also a frequent speaker at conferences, a prolific blogger on LinkedIn, and recently a developer of building science YouTube videos.
One of his most appreciative audiences may be Addison Homes’ clients. For every home buyer, Usher prepares a 75- to 100-page homeowners manual that includes explanations of all systems in the home with warranty and maintenance information.

He also makes house calls. “We are always available to past clients for questions and consultation. We have also started to offer home maintenance services, where we monitor and maintain the systems in our past clients’ homes on service agreements,” Usher says. “We firmly believe that continuing relationships and service after the sale is absolutely critical for zero energy homes because of the lack of understanding of high-performance homes in the market among contractors.”

The attic is insulated on the underside of the roof deck with 8 inches of open-cell spray foam, providing an insulated space for the small-diameter HVAC ducts.

An 80-gallon heat pump water heater is internet connected and has leak detection with an automatic shut off valve. A smart recirculation pump speeds hot water to faucets for shorter wait times and less water loss.

Extensive air sealing with tape, elastomeric caulk and wide-spray canned foam helped the builder achieve an exceptionally tight home with a leakage rate of 0.7 air changes per hour at 50 Pascals pressure differential.