Habitat’s High-Performance Experiment
Habitat for Humanity affiliates around the country have launched net-zero energy and Passivhaus projects which are often the first in their communities
High-performance houses might not seem the most logical choice for Habitat for Humanity, a non-profit that builds affordable housing on tight construction budgets and relies on non-professional labor.
Renewable energy systems have high upfront costs, and the extra insulation, air-sealing and other detailing that make Passivhaus or net-zero energyProducing as much energy on an annual basis as one consumes on site, usually with renewable energy sources such as photovoltaics or small-scale wind turbines. construction possible take more time, building expertise and money than conventional houses.
But Habitat affiliates around the country are beginning to build these high-performance designs and offering them to families that ordinarily would be priced out of the market.
Projects are currently underway in many parts of the country, including Washington, D.C., Missouri, California, Minnesota, and Wisconsin. It’s a homegrown trend taking root without any directive from Habitat’s international headquarters in Atlanta; each Habitat affiliate is a separate entity that makes its own decisions about what kind of housing to build.
Net-zero, Passivhaus and other high-performance designs are still a fraction of the total number of Habitat projects, accounting for roughly 1% of the 3,800 new housing units that Habitat built in the U.S. last year. But for a variety of reasons, local Habitat affiliates are now more likely to try these cutting-edge designs, and over time that will mean much lower utility and maintenance bills for the homeowners lucky enough to get them.
In some cases, the Passivhaus projects are the first to be built in the community by anyone. Here’s a rundown on several projects around the country.
In the nation’s capital, a first
Habitat for Humanity of Washington, D.C. took advantage of the biannual U.S. Department of Energy’s Solar Decathlon to jump into high-performance housing.
Until 2011, the design competition for college students, sponsored by the U.S. Department of Energy, had taken place on the National Mall in Washington. When it was over, these demonstration homes were dismantled and sometimes junked, says Heather Phibbs, Washington Habitat’s director of marketing and development.
But in this case, the Parsons School for Design and the Stevens Institute of Technology approached Habitat and suggested a partnership to turn its Decathlon entry into housing for a Washington, D.C., family. When the Decathlon ended, the project, called the "Empowerhouse," was taken apart, moved to a site in the Deanwood neighborhood in the northeast part of the district and turned into a duplex.
The project was certified by the Passive House Institute U.S. and built to operate as a net-zero energy home.
"It was the first time we had built a Passivhaus, Habitat for Humanity of DC, and it was the first Passivhaus ever built in DC," Phibbs said.
Based on this success, there are now a number of organizations thinking of ways to turn these demonstration houses into homes when the Decathlon competitions end, Phibbs says. (For more information on the Empowerhouse, see Two Solar Decathlon Homes Get High Marks for Affordability.)
The Empowerhouse is just a beginning
The Habitat affiliate has since launched six Passivhaus projects in Ivy City, a part of the city where it and two other nonprofits are building a total of 60 affordable housing units.
Working with money from the Department of Housing and Urban Development and land grants from the city, the Habitat affiliate has been building a total of 30 housing units. Six of the 11 housing units in the last phase of this project are designed for Passivhaus certification.
Conditioned spaceInsulated, air-sealed part of a building that is actively heated and/or cooled for occupant comfort.
: 1,404 sq. ft.
Number of floors: 2.
Bathrooms: 1 1/2.
Construction: 2x4 stud wall with 9 1/2-in. I-joist balloon framed wall on the outside.
Type of foundation: Slab.
Windows: Klearwall Future-Proof triple-glazed, argonInert (chemically stable) gas, which, because of its low thermal conductivity, is often used as gas fill between the panes of energy-efficient windows. -filled.
Ventilation: Energy-recovery ventilator(ERV). The part of a balanced ventilation system that captures water vapor and heat from one airstream to condition another. In cold climates, water vapor captured from the outgoing airstream by ERVs can humidify incoming air. In hot-humid climates, ERVs can help maintain (but not reduce) the interior relative humidity as outside air is conditioned by the ERV..
Domestic hot water: AO Smith Cirrex solar electric.
Heating and cooling: Single wall-mounted ductless minisplit.
Insulation: Above the slab, 6 in. of XPSExtruded polystyrene. Highly insulating, water-resistant rigid foam insulation that is widely used above and below grade, such as on exterior walls and underneath concrete floor slabs. In North America, XPS is made with ozone-depleting HCFC-142b. XPS has higher density and R-value and lower vapor permeability than EPS rigid insulation., followed by 3 1/2 in. of mineral wool, R-49. Above-grade exterior walls, Roxul mineral wool in 2x4 structural wall, dense-packed cellulose in balance of wall, R-45. Roof, 8 in. polyisocyanurate foam, R-49.6.
Blower-door testTest used to determine a home’s airtightness: a powerful fan is mounted in an exterior door opening and used to pressurize or depressurize the house. By measuring the force needed to maintain a certain pressure difference, a measure of the home’s airtightness can be determined. Operating the blower door also exaggerates air leakage and permits a weatherization contractor to find and seal those leakage areas.: Not yet available.
Cost of construction: $172/sq. ft.
Conditioned space: 1,248 sq. ft.
Number of floors: 1.
Bedrooms: 3, plus large loft.
Construction: 2x6 stud wall built with advanced framingHouse-framing techniques in which lumber use is optimized, saving material and improving the energy performance of the building envelope. techniques.
Type of foundation: Slab.
Windows: Triple-glazed Jeld-Wen.
Ventilation: Energy-recovery ventilator.
Domestic hot water: Solar thermal with electric backup.
Renewable energy: 8 kW photovoltaic(PV) Generation of electricity directly from sunlight. A photovoltaic cell has no moving parts; electrons are energized by sunlight and result in current flow. system.
Heating and cooling: Ductless minisplit air-source heat pumpHeat pump that relies on outside air as the heat source and heat sink; not as effective in cold climates as ground-source heat pumps..
Insulation: Under slab, 4 in. of rigid foam. Exterior above-grade walls, a combination of open-cell foam and blown-in cellulose with 2 in. of rigid foam on exterior, R-30. Roof, 1 1/2 in. open-cell foam plus blown-in cellulose, R-60.
Blower-door test: Not yet available.
Cost of construction: $85/sq. ft.
SANTA BARBARA, CA
Conditioned space: 3,749 sq. ft. (total for three units)
Number of floors: 3.
Bathrooms: 3 full, 3 half.
Construction: 2x6 exterior walls, built with advanced framing techniques.
Type of foundation: Slab.
Windows: Double-glazed Simonton.
Ventilation: Heat-recovery ventilator(HRV). Balanced ventilation system in which most of the heat from outgoing exhaust air is transferred to incoming fresh air via an air-to-air heat exchanger; a similar device, an energy-recovery ventilator, also transfers water vapor. HRVs recover 50% to 80% of the heat in exhausted air. In hot climates, the function is reversed so that the cooler inside air reduces the temperature of the incoming hot air. .
Domestic hot water and renewable energy: Combined Echo Solar System includes solar hot water and photovoltaics producing 4,000 kWh of electricity and 122 therms per year. Domestic hot water system also incorporates a tankless heater.
Heating and cooling: Wall-mounted electric resistance heaters; no air conditioning.
Insulation: None under slab. Most exterior walls have high-density fiberglass batts with 1 in. of rigid foam on the outside. Roof, 8.2 in. of open-cell foam under roof deck, R-30.
Blower-door test: Not yet available.
Cost: $110-$125/sq. ft.
"We’ve been working to green our practices as much as possible for a number of years," Phibbs says. "There’s a lot of sense that it makes, not only in leaving a lighter environmental footprint and keeping a house more efficient to run, but when you have a house that’s more efficient you’ve got maintenance costs a lot lower, which is really fitting for these lower income homeowners."
The 1,400-square-foot three-bedroom houses (see sidebar at right for more details) are more expensive to build than the kind of housing Habitat usually takes on — about $172 per square foot compared to a more typical $110 per square foot. The houses will sell for between $180,000 and $200,000, Phibbs says, with Habitat raising the money to fill in the gap between the sales price and actual construction costs.
Separately, Habitat has been contemplating a crowd-sourcing campaign so the houses can be equipped with photovoltaic panels.
Finding the right families
Habitat tries to identify prospective homeowners before or during construction so the families will have the chance to work on their own houses. In Washington, each family must contribute a total of 300 hours of sweat equity to quality for ownership, although they can still qualify by working on someone else's house.
"It’s a little bit of a trick to build these things affordably for Habitat families," Phibbs says.
The new owners of these Passivhaus homes will have incomes of between $30,000 and $60,000 a year, representing 30% to 60% of the median income in the area, which is $100,000 a year.
The lower operating costs for Passivhaus homes is a great match with families living on tight budgets. But it can be challenging to apply the Habitat model to houses that require a lot of construction acumen to build. All Washington Habitat projects involve some professional labor, and in the case of Passivhaus designs, Phibbs says, there’s just a little more of it.
"So the pieces of that process that our construction staff leads volunteers in are a little more limited during Passivhaus construction," she says. "There are segments of the process that they don’t allow volunteers to help with."
Despite the added complexities of construction and higher costs, the effort holds a great deal of promise for Habitat. "It’s the longterm benefit to homeowners (significantly lower utility costs), as well as interest among many of our funders," Phibbs said in a follow-up e-mail. "And our efforts to document the process and find ways to bring the costs down to a level that may make a greater number of these homes eventually achievable for us."
In Missouri, bidding for the future
Show-Me Central Habitat for Humanity entered the world of high-performance building at the invitation of the city of Columbia, according to Bill View, its executive director.
The city circulated a request for proposals among Columbia's housing development agencies asking for their most energy-efficient designs and offering $66,000 in seed money to the winner, View says. Among the few requirements were the use of either a ground-source heat pumpHome heating and cooling system that relies on the mass of the earth as the heat source and heat sink. Temperatures underground are relatively constant. Using a ground-source heat pump, heat from fluid circulated through an underground loop is transferred to and/or from the home through a heat exchanger. The energy performance of ground-source heat pumps is usually better than that of air-source heat pumps; ground-source heat pumps also perform better over a wider range of above-ground temperatures. or a ductless minisplit heat pump for heating and cooling, and a generous amount of insulation. Three other organizations offered bids, but the Habitat affiliate took home the prize.
It's the first Habitat project of its kind in Columbus.
"I wanted to win the bid, to tell you the truth," View says. "That's the honest part of it, although we've been building Energy Star homesA U.S. Environmental Protection Agency (EPA) program to promote the construction of new homes that are at least 15% more energy-efficient than homes that minimally comply with the 2004 International Residential Code. Energy Star Home requirements vary by climate. for a few years now. But when they put up $66,000 and said it's up for grabs to the person who gives us the best model for energy efficiency, I decided I wanted to win the bid."
That $66,000 is almost enough money to build another home for another family.
The house (see the details at right) is under construction and may be finished by late spring or early summer, depending on weather and other factors. The Habitat chapter has five or six other projects underway at the same time.
Net-zero by design
Designers originally considered a ground-source heat pump, View says, but the project's engineer suggested that using an air-source heat pump instead would free up $10,000 that could be spent on photovoltaic panels. Eventually, he adds, designers settled on an 8-kW system that on paper would make net-zero operation possible.
"So we just decided to splurge and put $20,000 worth of solar panels on it and see what happens," View says. "It engineered out to a net-zero house, but of course we won't know until it's up and running."
View expects the 1,248-square-foot three-bedroom house to sell for $107,000, exactly what Habitat will have in it. It's likely to go to a buyer with an income of as much as 80% of the median income in the area. Habitat houses there are typically sold to those making 30% to 50% of the median.
In California, LEED didn't have the “buzz”
Santa Barbara, California, is a wealthy community on the coast a few hours north of Los Angeles, and its local Habitat affiliate is one of several in the state building high-performance housing. It's difficult to find lots for single-family Habitat housing in Santa Barbara, says Alexandra Hamill, the affiliate's development manager, so they're concentrating on townhouses.
Their current project incorporates three buildings, one of which is a three-unit building which Habitat hopes will to have certified as a Passivhaus. It includes two three-bedroom units and one two-bedroom unit with a total of 3,749 square feet of conditioned space (see the details at right). The other two buildings will be built to the same standards, but Habitat won't seek Passivhaus certification for them.
Habitat's last project had been constructed to meet requirements of Built Green Santa Barbara, a local sustainable building program, says Jon Peterson, the affiliate's associated executive director.
"Really, our goal from a Habitat perspective of building green at all is we want to provide homes that will last a very long time, but also will be affordable," Peterson says, "and one of the ways is keeping the utility and maintenance costs down."
As they began design work on the townhouse project, architects from DMHA, a local firm, were aiming for Level 4 compliance with Built Green, which would have been a step up from Level 3 of the previous project. They also considered seeking certification under the LEED for HomesLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. program administered by the U.S. Green Building Council. But in the end, LEED didn't seem to offer what the affiliate wanted.
"It's been done by other Habitat affiliates," Peterson says. "It didn't have the buzz. In addition to building an affordable and secure house, one of the thing we look at is how will this help us with fundraising efforts. Although LEED is a good standard, paying for that certification didn't feel like the best option for us. "
Passivhaus emerges the winner
One of the architects working on the Canon Perdido project had a background in Passivhaus design, as did the construction manager, Peterson says, and that helped tip the scales. The building was relatively simple in shape, without any complex roof geometry, and it looked like a good bet for Passivhaus construction.
"Everybody was really excited at the idea of doing this, and it was a newer thing," Peterson adds. "We thought the community would be excited about it."
Habitat broke ground on the project in June 2013 and hopes to have it wrapped up by this summer. It will be the affiliate's first Passivhaus building.
Families that move into the townhouse will have incomes of between 40% and 80% of the area's median income, or $30,000 to $60,000 a year, Hamill says.
There were 100 applicants for the dozen housing units in the project. Although Habitat officials were thrilled to be working on a Passivhaus project, they didn't advertise that aspect of the project to the public, and neither Hamill nor Peterson thinks the benefits of living in a Passivhaus were obvious to people who applied to live there, or even the people who worked on the buildings.
"Every time we have volunteers at the site, we tell them about the project and they're fascinated by the Passivhaus side of it," Hamill says, "but for the most part I don't think the community understands."
That said, Peterson adds, a local American Institute of Architects tour of the project was the most well-attended in some time.
Not right for every local affiliate
High-performance buildings are intriguing to builders looking for new challenges, but they represent a very small fraction of the houses that Habitat builds, and very few affiliates around the country are tackling them — only 15 of the nation's 1,500 total, according to Derek Morris, director of construction technologies for Habitat for Humanity International.
Roughly three-quarters of new Habitat houses are built to Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners. standards, but going the extra mile for Passivhaus or net-zero performance isn't always the best use of limited resources, Morris says.
Affiliates that do make the leap have started by learning the basics of energy-efficient designs, embracing advanced framing techniques and air-sealing, for example, or learning how to orient houses correctly on the site. Once they've mastered those things, he adds, net-zero or Passivhaus construction is a more attainable goal.
But all decisions are local, he says, as affiliates focus on Habitat's "number-one objective," the elimination of poverty housing.
"Part of the challenge is always the allocation of resources," he says. "As you're doing Passivhaus or net-zero, you end up having a greater upfront investment in it. If you have the ability to do one home, that's great, but what do you do about the other homes that are needed in the area?
"In some cases, it's the appropriate decision to go forward with net-zero or Passivhaus if that's appropriate for your local environment and your local needs," Morris continues. "In others, it may be that instead of doing 20 net-zero homes we do 30 Energy Star homes. It's a decision that always has to be made locally. It's never a one-size-fits-all solution."
- Habitat for Humanity of Washington, D.C.
- Show-Me Central Habitat for Humanity
- Habitat for Humanity of Southern Santa Barbara County
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