ZERH Attached Home Winner
This award-winning attached home in a 10-lot infill development in Salt Lake City showcases panelization and other high-performance features.
It’s been said that you can’t have quick, cheap and quality at the same time. Don’t say that to the team at Garbett Homes, which has mastered the ability to provide all three elements during its home building efforts.
Panelized construction—which enables a home to be completed in as little as a few days, compared to several months or even years with other methods—is one way the Salt Lake City-based builder is able to cost-effectively produce high-performance homes that meet all requirements of the U.S. Department of Energy (DOE)’s Zero Energy Ready Home (ZERH) certification.
Project Name: Sterling at Capitol Hill, Salt Lake City
Builder: Garbett Homes, Salt Lake City
Completed: December 2021
Garbett’s efforts helped the company to win its first Grand award in DOE’s Housing Innovation Awards competition in 2022, in the Attached Homes category.
“Panelized walls are a great way to reduce construction waste and improve building timelines, and they can also improve the homes’ energy efficiency,” says Garbett Homes Land Acquisition and Energy Coordinator Damian Mora.
Garbett Homes is a production builder of single-family detached and multi-
family homes for sale and for rent. Started by Bryson Garbett in 1983, the builder turned to higher efficiency homes in 2008 and committed to certifying all of its homes as DOE ZERHs in 2017.
Mora notes that Garbett is Utah’s leading builder of DOE ZERHs, with almost 600 certified homes (the next-closest Utah builder has 12).
“We like that the program sets a standard that is above and beyond local codes but is achievable for any builder interested in achieving high performance,” Mora says. “We like that it also goes beyond efficiency and includes comfort, durability, and indoor air quality. [And because it] is recognized locally by loan financing entities, that allows us to get great interest rates on long-term financing for rental projects.”
Infill Project: Preparation and Planning
The winning home is an attached home in a 10-lot infill development in Salt Lake City, down the street from the Utah State Capitol in the vibrant Capitol Hill neighborhood. The site was on a hillside requiring extensive excavation and the installation of massive retaining walls.
A simple gable roof designed to withstand heavy snow loads gives the Sterling at Capitol Hill project a modern look while remaining practical. The roof’s low pitch makes it appear to be flat from the front and rear street level.
The builder also had to plan for the Salt Lake area weather: Salt Lake City is located in the foothills of the Wasatch Mountains and gets 54 inches of snow annually, which influences materials, design, and site planning.
Garbett constructed its homes to be solar ready. All are pre-wired for solar and the roof is engineered to withstand future solar photovoltaics (PVs) on any portion of the roof regardless of floor plan. All Garbett Homes are now electric vehicle (EV)-ready, with a 220-volt outlet installed in the garage of every home. “Despite the infill location, the Sterling at Capitol Hill homes have great solar access,” Mora says.
To ensure consistency and help control costs, the builder includes a comprehensive energy-efficiency package with insulation, air sealing, and indoor air quality measures that is implemented on all of its homes to ensure they achieve ZERH standards.
Construction starts with site preparation. All homes come with a lot-specific grading and drainage plan to direct runoff away from the homes and protect them from the damaging effects of water. “We can have several feet of snow on the roof and perimeter of the home during the winter so a comprehensive drainage plan is critical to ensure the longevity of our homes,” says Mora.
To meet the demands of the cold climate, Garbett packed R-23 of blown fiberglass into the 2-by-6 walls, which were built using advanced framing techniques such as 24-inch on-center stud spacing, 3-stud open corners, and open headers over windows and doors to maximize the room available for insulation. The walls of the attached homes were sheathed with 7/16-inch OSB sheathing and house wrap, then covered with 20-gauge stucco netting and 3/8-inch cement base coat stucco, brick, or fiber cement lap siding.
“Advanced framing is not widely used in Utah, so Garbett found that training our trade partners was essential,” Mora says. “We train regularly to get new framers on board quickly. In a production home setting, it is important to have everyone familiar with the techniques to get the most consistent and highest performance out of our homes.”
Garbett employed a vented attic with 15 inches (R-60) of blown fiberglass insulation on the attic floor. Over the 7/16-inch OSB sheathing, the builder installed two layers of #15 roof felt and asphalt shingles. Garbett specified trusses with 12-inch raised heels to allow more insulation over the top plates. All of Garbett’s house plans are designed with raised energy heels to maximize the insulation in the attic and above the exterior walls.
The project used a very simple roof design with one low gable running east-west at a 3/12 pitch for the full length of the building except for one small section of roof at a different height to separate the two units of this attached dwelling. A simple roof design provides many benefits in terms of cost and labor savings: fewer complicated details for water management and air sealing; simple installation of insulation, sheathing, and siding; more space for solar panels.
Garbett Homes meets the requirements of the EPA Indoor airPLUS program by including low- or no-VOC emitting paints and finishes, carpet, carpet pad and adhesives, and cabinetry.
The attached homes also have a full daylight basement. The below-grade walls of the walk-out basement are waterproofed with a spray-on sealant. The builder installed R-10 of rigid foam insulation under the full slab. The concrete walls at the back of the basement were covered with framing. The above-grade walls at the front of the lowest level are also 2-by-6 framed walls at 24 inches on center. All framed wall cavities were filled with R-23 of blown fiberglass.
The double-pane, vinyl-framed windows have low-emissivity coatings to discourage heat transmission but no gas fill due to the altitude. They provide a U-factor of 0.27. Because Salt Lake County is a predominantly heating climate, the windows have a higher solar heat gain coefficient of 0.35 in strategic places so they can provide beneficial solar heat gain that offsets heating demand in the winter.
Garbett has recently shifted its air sealing strategy to include a whole-house technology that includes spraying an aerosolized acrylic into the home while it is pressurized. The tiny beads of acrylic adhere to the edges of cracks in the building envelope, accumulating to fill in and seal off air leaks during the 2-to-4 hour spraying process.
The aerosolized acrylic sealing process can be used on all cracks under 0.5 inch. Before applying the process, the builder’s crew applies canned spray foam and drywall gasket around all penetrations in the building envelope.
Correctly installed house wrap with all seams and edges taped is also a critical air sealing measure. “Before, we relied more on spray foam in the rim joists and attic for our air sealing, but we have reduced our use of it because of some issues we had with cracking and ineffective application,” Mora says. “However, we will still use spray foam if a portion of the house will be covered before the aerosolized acrylic is applied.”
To provide fresh air to the home, Garbett installed an Energy Recovery Ventilator (ERV). The ERV has separate ducts to bring in fresh air and exhaust stale air. The ducts pass in a heat exchanger, where heat from the warmer duct is passed to the cooler duct, helping to warm up incoming air in winter and cool incoming air in summer. In addition to the ERV, an exhaust fan in the hall bathroom is set for continuous operation.
Garbett installed a high-efficiency, high-capacity tankless gas water heater in the multifamily unit, with an energy efficiency factor of 96 percent. The water heater is equipped with a button-activated recirculation pump to speed hot water to taps that are further from the water heater. Garbett also installed low-flow U.S. Environmental Protection Agency (EPA) WaterSense-labeled plumbing fixtures and ENERGY STAR-certified appliances to reduce water usage in the house.
To meet DOE ZERH specifications, Garbett focuses on construction quality. The construction team meets weekly to discuss quality control measures and also has pre-construction meetings with homeowners. Site managers are required to perform quality checks at various stages of construction, request fixes if needed, and report on the progress and quality of each home.
The sales and construction teams meet periodically to do frame and insulation walks to find any potential problems with processes and plans and to identify ways to improve on them.
“We work closely with all trade partners and energy raters to ensure all aspects of our high-performance standards are met,” Mora says. “We have frequent trainings for our construction team and trade partners to keep up to date on all ENERGY STAR and [DOE ZERH] standards.”
Staff are required to attend local energy-efficiency trainings and workshops. “Having everyone educated to know what their part is in building a [ZERH] is crucial for maintaining quality construction and consistency,” Mora adds. “[And,] we recently worked with outside consultants to improve our processes, product and relationships with our buyers and trade partners.”
In addition to the DOE award, Garbett Homes was recognized for its efforts with a Bronze Award in the 2020 National Housing Quality Awards.
Air sealing: 3.49 ACH 50. Taped house wrap; whole house aerosolized acrylic sealant.
Appliances: ENERGY STAR refrigerator, dishwasher, clothes washer.
Attic: Vented attic; 16-inch R-60 blown fiberglass; 12-inch raised-heel energy trusses.
Energy Management System: Programmable thermostat.
Hot Water: Gas tankless, 96 percent EF. Push-button hot-water recirculation system.
HVAC: Gas furnace, 96.5 percent AFUE, ECM motor; air conditioner 15 SEER.
Lighting: 100 percent LED.
Roof: Truss gabled and shed roofs: 16-inch R-60 blown fiberglass, 7⁄16-inch OSB, #15 felt, asphalt shingles.
Solar: PV ready, wiring in place, roof will support panels.
Ventilation: ERV, 66 percent SRE; integrated with central air handler. MERV 8 filter in air
handler, MERV 6 filter in ERV. Exhaust fan runs continuously at 50 CFM.
Walls: 2-by-6, 24-inch o.c., panelized, R-23 total: advanced framed, 5.5-inch blown fiberglass in cavity, 7⁄16-inch OSB, house wrap, 20-gauge lath, 3⁄8-inch cement base coat stucco.
Water Conservation: EPA WaterSense push-button recirculation pump. “Localscaped” mix of patios, play areas, bark mulch, local plants, and grass.
Windows: Double-pane, low-e, vinyl frame; single-hung and sliders. U=0.26, SHGC=0.31.
Other: Panelized walls. No/low-emission products.