A group of architecture students from Prairie View A&M University has won top honors in this year’s Department of Energy Race to Zero student competition with an affordable home designed for a Houston, Texas, neighborhood.

The team of eight students, led by adjunct assistant professor Shelly Pottorf, are from the A&M School of Architecture and were among 31 collegiate groups representing 23 institutions from around the country. Results were announced earlier this month at the National Renewable Energy Laboratory in Golden, Colorado.

In its report on the project, the group said it designed the three-bedroom, 1,567-square-foot home to fit in an urban neighborhood called Independence Heights, an area with narrow lots and a 40% vacancy rate. Their idea was to develop clusters of single-family homes into “pocket communities” with shared open space.

The lot the group selected for development is a 15-minute drive from downtown Houston, but only a 1-minute walk to a public bus stop, and within biking distance to a light rail stop. It’s also next to a community garden.

“Community residents expressed a desire for the concept to be inspired by the modest efficiencies of a ‘shotgun’ vernacular home,” the project report says. “A home style native to the area, the ‘shotgun’ was designed to allow for natural ventilation and fit the long narrow lots. Design features include a gable roof, rectilinear floor plan with side circulation, front deck, and wood cladding.

“Adding the second level to the ‘shotgun’ home increases the livable area for contemporary families,” the report continues. “This provides a home design for families who have moved away an opportunity to return to the neighborhood without giving up living space they may have found in other suburban areas, further outside of downtown Houston, jobs, and schools.”

Because the neighborhood is in Houston’s 100-year flood plain, and has experienced severe flooding in the past few years, the house sits 4 feet above the ground on concrete piers. The climate is hot and humid.

Affordability was important

Designers had high goals: meet PHIUS+2015 requirements and make the house net-zero ready. But costs counted, too.

“Independence Heights is home to an aging population; the younger generation has moved out due to lack of new housing, dilapidated homes, and high vacancy rate; 41.6% of the population in Independence Heights lives below the poverty line, as opposed to the 23.8% in Houston,” the student report says.

The house was designed with a $160,713 purchase price in mind. That would keep the percentage of household income spent on housing — including principal, interest, property tax, and insurance — at 37% of the Texas average mean income, or $1,572 per month.

Getting to net zero

To reach net-zero energy and PHIUS+2015 performance in Houston, designers included radiant barriers in both the roof and wall assemblies. A standing-seam metal roof is installed over a 3/4-inch ventilation cavity. In the walls, foil-faced insulation faces a 3/4-inch cavity. A rainscreen assembly further reduces heat gain.

The project has a HERS Index score of 36 without photovoltaic panels, with estimated electricity consumption of 6,872 kilowatt-hours (kWh) per year. With a 6.3 kW PV array, the HERS Index drops to -9. Energy costs were modeled at $756 per year.

Here are some other building features used in energy modeling:

• Insulation: In the roof, there’s R-38 of cavity insulation plus R-9 of continuous insulation on top of the roof deck. Wall insulation consists of R-21 in cavity insulation plus another R-9 over the sheathing. The floor is insulated to the same level as the exterior walls.
• Ventilation: Ultimate Air energy-recovery ventilator.
• Windows: Double-pane Passivhaus-certified windows with a solar heat gain coefficient of 0.2 and a whole-window U-factor of 0.15.
• Domestic hot water: 80-gallon heat-pump water heater.
• Airtightness: 0.6 air changes per hour at a pressure difference of 50 pascals.
• Space conditioning: SEER 23 minisplit air-source heat pump.

Team members included Sean Benson, Alexis Borman, Chris Brown, Desirae Price, Graciela Tendilla, Taylor Hudson, Devonta Magee, and Yasmine Parker. All are candidates for a bachelor of science degree in architecture this year or next.