7 Habits of a Super Energy-Efficient House
One of the nation’s most energy-efficient model homes doubles down on the concept of sustainability. In accordance with its “net zero” breeding, KB Home’s “Double ZeroHouse 2.0” is equipped to produce as much energy as it consumes. The annual utility bill – if there were one – would be $0. But the Double ZeroHouse is also designed to use zero freshwater irrigation – hence the “double zero.” The efficient model home for a family of four in Lancaster, Calif., opened early in 2014, recycles household shower, bath, kitchen and laundry water, eliminating the household’s need for fresh water to maintain the plants in its landscaping. KB Home began rolling out its first net-zero models in 2011, one of a few builders launching highly energy-efficient, production-scale homes in limited markets. The savings are remarkable. KB Home estimates that the Double ZeroHouse uses 70 percent less water than a typical resale home with landscaping, conserving 150,000 gallons of water annually. All told, with green building, solar technology and energy management systems, the house saves about $4,452 annually in water and energy bills, according to KB Home. The cost of adding the ZeroHouse technologies to a built-to-order KB Home starts at about $50,000. “We have a mantra: reduce before you produce,” says Jacob Atalla, vice president of sustainability for KB Homes. “The mechanics of the home have to work as a system.” Here’s a look at a few of the eco-smart features:
1Walls Well-insulated walls are the biggest factor in reducing the amount of energy needed to heat or cool a home. “You have to start with the envelope,” Atalla says. “It’s like a thermos where you can put a cold drink in and keep it cold, or a warm drink in and keep it hot. The envelope of a house traps heat or cool air inside and keeps it from escaping.” The Double ZeroHouse has a double layer of insulation: a regular density layer on the inside, moving to high density closer to the wall’s exterior. The walls are reinforced with foam boards, which seal air.
2Windows Improperly insulated windows can also let extra warm or cool air out of the house. KBHomes seals argon gas between the double-paned, treated windows to create better insulation, Atalla says. The low-energy window treatment and the argon help regulate how much heat from the sun goes into the home, and protect the furniture from UV damage.
3 Tankless water heater Unlike a more traditional water heater that constantly heats up water, this type of water heater only uses energy when signaled. The average household wastes 3,650 gallons or more per year running water until it’s hot enough to use, according to WaterSense, an EPA program, so savings from the tankless technology add up quickly. The U.S. Department of Energy (DOE) estimates that tankless heaters may be more than 20 percent more efficient than their constantly warm counterparts in households that use less than 41 gallons of water a day.
4 Water recycling Most of the water used in the house, from showers, tubs, sinks and washing machines, is captured, treated to near-potable quality and recycled for use in the landscape. The graywater is stored in two tanks, one that collects the graywater and a second that stores treated water until it’s needed for irrigation. The home recycles up to 40,000 gallons annually. The home’s dishwasher, a KitchenAid Architect Series 11, also recycles, saving the water used in the last rinse cycle to use for the first pre-rinse cycle of the next load. It uses 33 percent less water than other highly efficient dishwashers.
5 Graywater heat recovery Water heating accounts for 20 to 30 percent of a home’s total energy consumption, according to the Department of Energy. The graywater recovery system in the Double ZeroHouse includes a process for extracting heat from outgoing used water in order to preheat new water coming into the home. When water goes down the drainpipe, it passes through copper coils that extract the heat. The heat is transferred into a series of smaller tubes that carry the colder incoming water. The incoming water preheats, reducing the work and energy use required from the water heater. “Water coming in to the home at 40 degrees might suck another 10 degrees of heat from the old water, so it becomes 50 degrees,” Atalla says.
6 Solar roof Solar panels may be the most recognizable energy-saving feature of the Double ZeroHouse 2.0. The high efficiency photovoltaic system from SunPower works with other energy-efficient features to produce the energy needed to operate the home. The parts of the roof free of the solar panels use reflective tiles that efficiently reflect sunlight and help control the temperature inside the home.
7 Smart, efficient appliances The home’s smart refrigerator shifts its most energy-intensive functions to off-peak times, using electricity when it costs least. The refrigerator, washing machine and dishwasher are all Energy Star rated. The washing machines use 35 percent less water and energy, and certified dryers use 20 percent less energy than the minimum efficiency standard, according to Energy Star. Rated dishwashers are supposed to use five percent less energy and 15 percent less water, while ENERGY STAR-rated refrigerators are up to nine percent more energy efficient.