Carl Ramsey’s home is conventional in only one respect—its aesthetics. His one-story house, with plank siding and a standing-seam metal roof, blends tastefully with other homes in the area. But that’s where the similarities end. The home performs head-and-shoulders above the rest, having earned a platinum rating from the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) program.
The home’s success relies on blending time-tested strategies, such as passive solar design and rainwater harvesting, with modern, high-tech systems. A grid-tied PV system and wind turbine provide electricity. Solar hot water collectors supply domestic hot water and heat for the radiant floors. Biological and environmental solutions include ultraviolet water purification, a greywater system, and an automated indoor air-quality system. Add environmentally friendly materials and finishes, and you get a comfortable, healthy, beautiful, and efficient home that is net-zero energy, net-zero carbon, and net-zero water.
Carl, an architect specializing in energy-efficient design, wanted a home that would provide its own potable and irrigation water and its own energy, all with minimal environmental impact. Since the goals of the project fit so closely with the LEED guidelines, Carl registered the project in a pilot program: LEED for Homes. To earn the platinum certification, the construction materials and methods had to minimize the home’s environmental impact, plus meet stringent energy performance levels (see “Scoring Sustainability” sidebar).
PASSIVE HEATING. The house was designed with a very long east-west axis to maximize exposure to the south. During the winter months, south-facing windows admit solar gain. A concrete block wall that traverses the center of the home along the east-west axis stores the solar heat. Additional thermal mass is provided by the 1 1/2-inch concrete radiant floor. During the summer, when the sun is high in the sky, roof overhangs shade the south-facing glass to minimize solar gain. Mass and windows were optimally sized using Energy-10 modeling software (see “A Model Home” sidebar).
PASSIVE COOLING. One of the home’s features is a specially designed dormer and clerestory in the middle of the roof that functions as a passive “cooling tower.” The opening of those windows is computer-automated. When a sensor measures a certain temperature, the windows open to exhaust warm air, creating a natural convection current that draws cooler air into the home through windows at lower levels.
EFFICIENT CONSTRUCTION. Exterior walls were constructed of 8-inch-thick structural insulated panels (SIPs), made with expanded polystyrene foam sandwiched between 1/2-inch-thick oriented strand board (OSB), providing R-36 insulation. SIPs offer superior insulation and little air infiltration, allowing more precise control of the interior environment.
With good structural strength, the panels eliminated the need for additional framing, and still met local building codes. SIPs also generate less waste from trimming and reduce labor costs, while more easily staying within building tolerances by requiring fewer pieces to construct a wall. OSB is made of wood chips from renewable forests, and the small pieces of wood make use of more of the tree than does the milling of studs.
For non-bearing walls, headers were eliminated. Bearing walls use headers individually sized for specific locations, instead of the traditional 2 by 10s. Interior framing uses a 24-inch stud spacing instead of the 16- or 12-inch spacing. Studs line up with bearing points at walls, floors, and ceilings, decreasing the need for additional framing at structural points. Finally, all the walls use only one top plate instead of the traditional two-plate system. Instead, small metal plates connect the top plate to the studs. Drywall clips hold the wallboard in place and reduce the framing corners from the traditional three studs to just two.
SMART LIGHTS. A daylighting plan with well-placed windows and a clerestory ensures that the home is flooded with natural light. SolaTube insulated, concentrating skylights are placed strategically throughout the home. These fixtures redirect natural light through a reflective insulated shaft into the residence. Lighting fixtures are all Energy Star-rated and use compact fluorescent bulbs.
The house features high-performance, low-e coated windows to reflect, or absorb, solar energy, and to reflect UV light. The exception is the south-facing windows, which use traditional glazing to maximize solar gain.
AUTOMATED AIR QUALITY. In most homes, exterior air infiltrates through tiny holes and cracks in the building envelope, allowing uncontrolled air exchanges (stale air out and fresh air in). But the Ramsey home is very tightly sealed—so tight that measurable natural air exchanges cannot occur. Instead, an automated heat recovery ventilator (HRV) with a high-efficiency particulate air (HEPA) filter provides fresh air to the interior. An exchange manifold captures most of the warmth or “coolth” prior to exhausting the stale air, and transfers it to the incoming air. The HEPA filtration system traps dust, pollen, mold, bacteria, and vapors to prevent them from entering with the fresh air. The HRV system exchanges three whole-house volumes of air every 24 hours, while minimizing heating and cooling energy losses.
A steam-electrode humidifier maintains interior humidity levels at 40%—considered optimum for a dwelling. The home’s automated management system adjusts the humidity, temperature, and airflow to keep the interior of the home comfortable.
ECO-FRIENDLIER PRODUCTS. Environmentally friendly interior finishes include earthen plaster finishes applied directly over drywall, OSB, and other interior building materials. Renewable-cork floors, clay-painted ceilings, and concrete countertops infused with recycled glass aggregate and fly ash (waste ash from power plants) augment the list of eco-friendlier materials. Locally harvested and milled beetle-killed ponderosa pine was used for the wood cabinets and base, window, and door trim.
MATERIAL SAVINGS. Through material reuse and recycling, the Ramsey home’s construction waste was reduced to about 0.4 pounds per square foot, or 1,000 pounds total. A similarly sized but conventionally built home generates more than 12 times this amount—an average of 5 pounds of waste per square foot of building. Waste wood and gypsum board were ground and used as soil amendments, and leftover concrete and block were ground and used on the gravel road and as a paving base. Metal, cardboard, and paper scraps were recycled.
SOLAR ELECTRICITY. A 7.2-KW, grid-tied PV system provides the home’s primary electricity. The building-integrated system also functions as a carport and was awarded additional LEED points for shading “hardscapes” (primarily patios, driveways, and other paved-over areas).
Electricity use for the home was estimated to be about 39 KWH per day, including four electric water heaters that serve as backup for the solar domestic hot water and the solar radiant floor heat (two for each application). The PV system was designed to provide about 79% of the total loads, averaging 31 KWH per day.
WIND ELECTRICITY. A 1.8-KW Skystream 3.7 wind turbine adds energy, especially from August through early October when afternoon thundershowers roll in almost daily, appreciably reducing solar-production but bringing a fairly reliable wind resource. The grid-tied turbine, manufactured by Southwest Windpower, sits on a 33.5-foot tower in an open field approximately 200 feet from the home. This reduces noise at the residence and provides unobstructed access to the wind when available. At a 9 mph average wind speed, we are producing 170 AC KWH per month.
SUSTAINABLE SPACE & WATER HEATING. The drainback SHW system, using six Apricus evacuated-tube collectors, provides winter space heating and year-round domestic water heating. Distilled water is pumped between the roof-mounted collectors and the first of two 250-gallon, unpressurized, insulated polypropylene storage tanks in the home’s mechanical room. The first storage tank houses the heat exchanger for DHW and also feeds heated water to the second tank through convection. Heated water is pumped out of this second tank via a temperature-controlled mixing valve, through two 30‑gallon electric backup heaters, and into the radiant floor heating system.
After it has run through the floor, the cooled water returns to the first storage tank. A tee in this water line, just prior to the return inlet on the storage tank, supplies the cold-water side of the temperature-controlled mixing valve. The DHW system draws hot water from the first storage tank’s heat exchanger. The cold water supply, at household pressure, is fed through the heat exchanger, through two backup electric water heaters and another tempering valve, and finally distributed to the household. Thermal pipe-runs are insulated with R-5 pipe insulation.
CATCHING RAIN. Without a well or connection to the municipal water supply, the home is completely water independent. A rainwater catchment system provides all of the home’s water needs, both potable and for irrigation. Gutters on the house and outbuildings direct water into eleven 3,000- to 5,000-gallon polypropylene storage tanks with a total capacity of 37,000 gallons. Based on an average annual rainfall of 21.35 inches and the catchment area, the potential harvest is more than 120,000 gallons a year.
SAVING WATER. Water-efficient plumbing fixtures for showers, faucets, and toilets reduce water use to 70% below the national average without compromising comfort or convenience. A greywater system collects wastewater from the bathroom sinks, bathtub, shower, and clothes washer, providing water for irrigation. On the LEED assessment, the home achieved a perfect score in the water efficiency category.
Faucet aerators were sized at a flow rate of 0.375 gpm, and shower heads are 1.5 gpm. Two Caroma dual-flush toilets consume 0.6 gallons of water to dispose of liquid waste and 1.2 gallons of water for solid waste; and the third toilet uses 1.1 gallons of water per flush. An Energy Star LG Electronics horizontal-axis clothes washer and dryer combo adds to the water savings, and offers some energy savings compared to conventional units.
REDUCING RUNOFF & RECYCLING WATER. A series of berms and swales across the property’s natural drainage paths help keep rainwater on site to reduce the need for supplemental irrigation. Native plants that are drought-tolerant and require minimal watering were used throughout. Supplemental watering comes from a drip-irrigation system fed by seven of the rainwater storage tanks and the greywater collection system. An automated control system monitors irrigation and shuts off the supplement if it senses rain.
RECLAIMING WASTE. The septic system provides complete treatment in a single precast concrete tank and relies on extended aeration, similar to that used in municipal wastewater treatment facilities. A UV light disinfects the effluent before releasing it to the leach field. Disinfection reduces the size requirements for the leach field and minimizes the possibility of contaminating groundwater.
According to Carl, “The extra cost for building ‘green’ can run from nothing to 5% or more, depending on amenities and methods. But the payback in reduced utility bills is considerable. At 2,720 square feet, the Ramsey home construction came in at $250 per square foot—very similar to typical custom homes in the region.
The cost of building this high-performance home was offset somewhat by federal, state, and utility incentives available. Arizona is a particularly attractive state when it comes to solar-electric system incentives. The state allows a tax credit of 5%, capped at $1,000, which combines with the federal tax credit of 20%, capped at $2,000. Through its Solar Partners Program, Arizona Public Service (APS, the local utility) offers a rebate of $3 per rated DC watt, capped at 50% of the system cost for residential systems.
At building time, there were no wind rebates available from APS. This has since changed, and APS now offers a “solar and wind” rebate. After incentives, the power system cost was $38,000. Other tax credits and rebates for using greywater, energy-efficient design, and energy-efficient construction techniques amounted to $3,275.
Don Joslin graduated from the San Juan College RE Program and is an RE systems project manager for Architectural & Environmental Associates (www.aeapower.com) in Flagstaff, Arizona.
Special thanks to Carl Ramsey, Jason Campbell, Chris Watson, Katy Johnson, Nathan Hodgson, and Radiance Heating and Plumbing for their assistance with this article.
U.S. Green Building Council • www.usgbc.org • LEED
Renewable Energy Systems:
Professional Solar Products • www.prosolar.com • PV mount
Sharp Solar • www.solar.sharpusa.com • PV modules
SMA America • www.sma-america.com • Inverters
Southwest Windpower • www.windenergy.com • Wind turbine
Green Materials & Finishes:
AFM Safecoat • www.afmsafecoat.com • Water-based door & trim stain/finish
American Clay • www.americanclay.com • Earthen plaster
Bricor Southwest • www.bricor.com • Low-flow faucets & fixtures
Capri Cork • www.capricork.com • Recycled rubber & cork flooring
Coroma • www.caroma.com.au • Dual-flush toilets
CrystaLac • www.crystalac.com • Water-based cabinet stain/finish
Kohler • www.us.kohler.com • Plumbing fixtures
Marvin Co. • www.marvin.com • Windows
Sea Gull Lighting • www.seagulllighting.com • Light fixtures