Habitat for Humanity of the Upper Keys helps make the dream of homeownership a reality for families that might not otherwise have the means to do so.
And at its latest construction site, Habitat and its crews — including the home’s future occupants, the Baustista family — are building a super energy-efficient, eco-friendly home that many dreamers would covet.
The Upper Keys affiliate of the international nonprofit housing organization has completed 23 homes since 1988. The two most notable features of its 24th home are the many energy conservation measures used in its design and construction and the rainwater harvesting system.
Once construction is complete, as early as November, Lisset and Miguel Baustista will be moving into the home with son Andy, 16, and daughter Amanda, 15. In the meantime, they’re putting in the 500 hours of work — known as sweat equity — required of them under the purchase agreement.
The building’s shell, including its roof and floor, are made of structural insulated panels. The panels consist of an insulating layer of rigid foam sandwiched between two sheets of engineered wood.
Local firm Solaria handled design and engineering for the energy- and water-conserving home.
" I remember as a child in social studies class, when the population of the world rolled over to a billion. I learned the U.S. had 5 percent of the population and consumed 25 percent of the resources. I thought, ‘That is insane.’ You can do more with less. You do that by understanding your world and designing to work with it, " said Steve Grasley, Solaria’s Marathon-based system designer.
The SIPs were made by Michigan-based PorterCorp. Once shipped to the Keys, the numbered sections were assembled by Habitat crews and CBT Construction. CBT owner Chris Trentine was able to use his experience from an earlier Key Largo home project that included SIPs.
Grasley said the SIP method helps trim the cost of building in Monroe County, where homes need to be elevated and hardened to protect them from water and wind damage. " Building up one level for our elevation adds 25 percent to the cost of a home, " Grasley said.
The average cost for traditional construction here is about $250 per square foot. With the SIPs’ simplified design, structural benefits such as an integrated foundation and minimized energy needs, a home like Habitat is building costs $120 to $150 per square foot, he said.
Grasley said the SIP materials might be slightly higher in cost than common block or frame materials, but SIP construction is stronger because of the materials and the engineering, cutting normal structural costs while producing a superior " structural envelope. "
The pre-engineered shell goes up quickly, which saves labor costs. A smaller air conditioning unit is used, due to insulation efficiency and smart design, and thousands of dollars are saved on both the unit and the electrical circuits needed.
Jack Niedbalski, director of Habitat for Humanity of the Upper Keys, noted: " The 1,189-square-foot home, even with its 16-foot-high ceiling expanse, is requiring only one half-ton air conditioning unit, which is Energy Star-rated and zoned to different parts of the house at different times of the day. "
Often the largest source of heat gain for a Keys home, the roof on this home is 10 inches thick, rated at R42 (resistance to heat flow) and finished with white metal roofing to reflect instead of absorb sunlight. (In comparison, common construction of a roof would average R30.)
The walls are 6 inches thick and provide R27 insulation compared to the average R11 wall. The 12-inch thick SIP floor delivers a R60 factor, far exceeding the average R5.
The three-bedroom, two-bath home features other passive energy-saving elements. The windows are placed to allow cross ventilation in mild weather, and a generous overhang around the house keeps the summer sun from striking the windows, minimizing heat gain.
Windows on the hotter south and west sides of the home are smaller, to minimize heat intake, and larger windows take advantage of the prevailing breeze on the east side of the house. The lot is also shaded to the west.
Many of the home’s efficient elements added little if any cost to construction and result in constant savings, a particularly important factor for affordable housing. A gas oven/range and clothes dryer and a 100-gallon solar water heater will cut electricity costs and contribute to an estimated bill of less than $60 a month. The estimated monthly cost for electric for a similarly sized house would be $250.
Grasley said the home will be engineered and rigged for solar panels, which can be added later. Those could produce enough electricity to offset the energy used to run the house.
The home’s 10,000-gallon cistern will provide water for the family of four, which is expected to use 3,000 gallons a month. If it is determined that the system is not meeting the family’s needs, a water meter and lines to the house can be installed using trenches predug for the future regional sewer system.
The cistern’s roof collection includes a first-flush system that allows the first minutes of a rain to wash the roof and run water away from the cistern line; then it automatically switches to collecting the clean water in the tank. As the water moves from the cistern, a triple-filter system provides water to the house and a high-performance filter supplies potable water in the drinking lines.
The home’s low-volume vacuum toilets don’t require much water. Aerated shower heads and faucets also maximize water economy. While the front-loading clothes washer will get plenty of use with a family of four, it uses half of the water of a traditional top loader.
— Karen Beal is a member of the Keyswide nonprofit Green Living & Energy Education. She writes about green living and the four Rs -- reducing, reusing, recycling and rot (compost). She can be reached at firstname.lastname@example.org.