Many of us recall when Habitat for Humanity began to make headlines more than 30 years ago, winning President Jimmy Carter’s support—he not only endorsed the organization but helped out with a hammer in hand. Since its inception in 1976, the nonprofit organization has built more than 250,000 houses, sheltering more than 1 million people in more than 3,000 communities worldwide.
Judging from its impressive number of new homeowners, Habitat has made huge strides in improving people’s quality of life. Now, the organization is beginning to build homes that are more energy efficient to make a long-term difference for the occupants and the environment.
On a stretch of land just north of Springfield, Missouri, Habitat for Humanity’s Legacy Trails housing development is offering a new paradigm of subdivision design. The focus has turned to establishing an environmentally friendlier neighborhood, with energy-efficient homes, native-plant landscaping, curbless streets to limit storm-water runoff, and bioretention swales that double as walking paths.
The newest home in the neighborhood—one designed and built primarily by Drury University architecture students—is a standout project that won recognition as the first-ever Habitat project attaining a LEED Platinum rating, a certification given for homes that achieve environmentally responsible and sustainable standards established by the U.S. Green Building Council.
The students, who designed the home as part of professor Traci Sooter’s design/build course, worked on its design over two semesters and construction over 31/2 months, starting in the fall of 2007. Sooter says that Habitat “builds in a somewhat sustainable manner, simply by constructing efficient, small-footprint homes.” But she was sure that her students could push the envelope further.
The student’s goal for the two-story home was to make it as sustainable as possible. From decisions for the form of the building at the design level to material and equipment selection, all aspects of the home’s construction were researched and considered by the team.
As design, material, and equipment decisions were made, the students rigorously researched the most sustainable—yet affordable—products and approaches. Cost is a big factor in a Habitat home, since affordability is tantamount to its mission of offering home-ownership to those who couldn’t typically afford it. One of the first strategies to make this an affordable, LEED Platinum home was to use passive systems and design to help heat and cool the home.
The home takes its shape from the sun, wind, and site, as well as from the restrictions and requirements of a Habitat four-bedroom home; it also has a nod to the typical building style in the area. Primary to the design process was conducting a site analysis—Sooter’s class researched prevailing winds and sun angles for the area and performed a site analysis at Legacy Trails.
The students designed the home to be longer on its east/west axis to increase southern exposure. This orientation maximizes solar heat gain in winter and also captures prevailing winds in the spring and fall, aiding in passive cooling.
Strategic placement of operable windows low on the south walls of the living, kitchen, and dining rooms allows air to enter from prevailing winds. High windows on the home’s northern side ventilate the warmed air. This allows the homeowner to keep the space cool longer before resorting to mechanical ventilation or cooling methods.
To lessen heat gain in the summer while still capturing the solar heat in the winter, the roof extends past the edge of the southern wall to shade the wall and windows from the high summer sun. The roof angles back to the same wall for aesthetic appeal. This approach allows the winter sun to hit the thermal mass of the concrete floor to collect and store radiant heat. The fifth-year Drury architecture students turned to their Mechanical and Electrical Equipment for Buildings text (see Access) to calculate solar angles and optimum square footage of glazing for the south façade of the home and its location. Heating systems manufacturer Watts Radiant then calculated loads to design the radiant heating system.
A 30-tube evacuated-tube solar hot water system provides about 70% of the energy needed for water heating. An electric boiler and an electric water heater provide backup for the floor heating and domestic water heating.
The rooftop-mounted collectors feed the heated propylene glycol antifreeze mix into an 80-gallon, twin-exchanger hot water tank. The glycol solution circulates in the superinsulated tank’s lowest coil, exchanging heat with the large volume of contained domestic hot water (DHW). In turn, the DHW shares its heat with the uppermost coil, which supplies the home’s two radiant heat zones.
During summer, the system reaches 160°F or higher. During winter, the solar array may heat the propylene glycol solution to about 110°F. Data from first few months of the home’s occupation show that the solar heating system can provide the majority of the domestic hot water—used for clothes washing, dishes, showers, and baths.
“Overflow” heat from the solar collector is expected to meet a small portion of the home’s radiant heat needs during the winter months, with passive solar contributing the majority, and the backup boiler making up the difference. If there’s abundant winter sunshine and the system produces all the DHW necessary, the system will assist with space heating.
To help meet USGBC LEED Platinum certification, the home also has dual-pane windows with low-e coatings, dual-flush toilets, and low-flow showerheads and faucets. All appliances and light fixtures are Energy Star-compliant.
Going through the LEED certification process, working directly with Guaranteed Watt Saver, the LEED for Homes provider, and working with Habitat for Humanity were great learning experiences for Sooter’s students. They gained practical, hands-on experience in resolving their design at full scale, plus they learned how the LEED certification process applies directly to a home and influences design decisions.
Working with Habitat for Humanity gave students the experience of investing in their community. In the Habitat model, homeowners put in sweat equity as part of their down payment. This placed the students side-by-side with the homeowner, building friendships while building a home for a family.
Designing and building a sustainable home was born out of Drury’s yearly convocation lecture series during the 2004-2005 theme year on sustainability. Members of the committee thought it would be great to create a sustainable project in which the entire campus could participate. And, in fact, they did—the construction launched with more than 300 first-year students prefabricating the exterior walls of the house.
This home was a Drury community project, where faculty, staff, and entire classes from various curricula volunteered their efforts. The home became a classroom for all. Each group was given an introduction to the home’s sustainable design principles, along with how they could make changes in their personal lives toward environmentally friendly practices.
Amy Pinegar, her three children, and one grandchild moved into the home last summer. She’s thrilled with her Habitat home.
“What is it like to live in my house? Well, it is constantly admired by people visiting the neighbors, or just passing by,” she says. “Everyone just loves it! Spring is my favorite time of year—not just because of weather, but the fact that the house has so many windows. No matter what direction the wind is blowing, it flows through the house.
When the sun shines during the winter, it can really heat the house up without the use of the radiant—just natural heat from the sun.”
Anna Codutti, director of development for Habitat for Humanity Springfield, looks forward to the home being a model for affordable green-builds nationwide. “It’s been an amazing experience working with Drury students and professors to turn the idea of creating an affordable, sustainable residence into an actual Habitat home,” Codutti says. “We learned a lot through the process, and I know it meant a lot to Amy that the students were so eager to involve her during all stages of the project.”
“This house may look different from the other homes in the subdivision, but it’s a great visual representation of what Habitat is trying to do with the community as a whole,” added Codutti. “Legacy Trails is a low-impact development, designed chiefly to show developers the affordability and long-term benefits of environmentally friendly infrastructure.”
“The residential sector contributes greatly to climate change and is responsible for 21% of U.S. carbon dioxide emissions,” said Michelle Moore, an executive with the U.S. Green Building Council. “Green homes like the Drury University project are an immediate and measurable way that individuals can make a difference for the environment—one family at a time.”
Manheim, Pennsylvania-based John Vastyan (717-664-0535) is a journalist and communications professional focusing on the plumbing, mechanical, radiant heat, and geothermal industries.
Traci Sooter, AIA, LEED AP, is an associate professor of architecture in the Hammons School of Architecture at Drury University in Springfield, Missouri. Formerly a general contractor in Springfield, Traci holds master degrees in architecture and construction management from Washington University in St. Louis, and a bachelors degree in marketing from Missouri State University. She specializes in design/build courses serving charities and communities in need.
Habitat for Humanity • www.habitat.org
Taylor Engineering & Consulting • firstname.lastname@example.org • Energy audit
Mechanical & Electrical Equipment for Buildings, Tenth Edition by Benjamin Stein, John S. Reynolds, Walter T. Grondzik & Alison G. Kwok (2005, Wiley)
Apricus Solar Co. • www.apricus.com • Evacuated tube collectors
Caleffi • www.caleffi.us • Solar pump station & accessories
Electro Industries • www.electromn.com • Boiler
Heat Transfer Products • www.htproducts.com • Solar storage tank
Watts Radiant • www.wattsradiant.com • Radiant floor heating components and hydronic control station
Allied Roofing Systems • www.alliedroofingsystems.com • TPO roof
Crete-Heat • www.crete-heat.com • Insulation panels for radiant floor tubing
Shaw Industries • www.patcraft.com • Carpet