‘Net zero’ house to be built in Maryland should produce as much energy as it uses
By Sandra Fleishman,
It sounds like an idea out of a sci-fi novel: a house that can produce as much energy each year as it uses. But most buyers aren’t interested in houses from a sci-fi novel, and they aren’t much interested in paying extra for them, either.
But a test house about to be built on a federal research site in Gaithersburg is designed to look like a typical home in the Washington area, and its inventors are going to great lengths to calculate how well the normal-looking sci-fi house would generate and consume energy when occupied by a family of four.
Groundbreaking is set for March 25, and construction is to begin in March or April, with completion expected in 15 months. Gaithersburg-based commercial builder Therrien Waddell Construction Group is the contractor, working with residential builder Bethesda Bungalows, which focuses on high-end “green” building.
The four-bedroom, three-bath house will be built with the latest in energy-efficient techniques and technology — plus redundant alternative-energy systems that will be tested later. It was designed by Building Science Corp. in Somerville, Mass. The two-story bungalow could be right out of Takoma Park, Hyattsville, Bethesda — or from Bethesda Bungalows’ new-project files.
The 2,700-square-foot wood-framed house with detached, electric-car-ready garage will sit on a small hill on the north end of the campus of the National Institute of Standards and Technology, near Clopper and Quince Orchard roads. The location is next to the institute’s engineering lab, where 50 or 60 scientists in the building environment division will monitor how the energy-saving technologies work when the home is in use. The $2.6 million research project was funded through federal stimulus money, after two years of preparation and design.
But no one will really live there. Instead, scientists will track what happens with a simulated family of four. “To simulate the family, the showers, toilets, lights and appliances will actually be turned on and off by computers . . . located in the detached garage,” says A. Hunter Fanney, chief of the building environment division. “The computers will send signals to every device in the home to control its operation. In the case of water [used in the showers, faucets and toilets], the computer will actually open and close the water valves to extract the correct amount of hot and cold water.”
Other automatically cycled appliances include a range with oven, a washer and dryer, microwave, dishwasher, and refrigerator with a door that opens and closes regularly.
Standing in for the parents and two kids, to generate body heat that will be factored into the energy-usage equation, “we’ll have people simulators — devices that are similar in appearance to little hot-water heaters that will give off heat and moisture to simulate humans” in every room, Fanney says.
The “people” will be turned on and off on schedule, too. The two heaters in the master bedroom and one in each of the kids’ rooms will go on at night when they’re “sleeping” and off in the morning when they leave for work or school. Units in the bathrooms will cycle on and off, as will heaters in the family room, dining room and kitchen.
The house also will have a 1,518-square-foot basement, complete with people simulators.
If the notion of human simulators and computerized utilities sounds cutting edge, it is. But Fanney says much of the “net-zero” building approach is within many homeowners’ grasp. Betsy Pettit, president of Building Science Corp., who served as the architect and building sciences consultant, agrees.
“In most buildings, you can lower energy usage by 40 to 50 percent by using existing off-the-shelf technology, if it’s selected properly, installed properly and maintained properly, and attention is given to detail,” Fanney says.
To reach net zero, the test house will have state-of the art energy-saving insulation, windows, ductwork, efficient heating and cooling units, Energy Star appliances, a solar photovoltaic array and solar thermal panels on the roof. They generate electricity by capturing energy from the sun during the day and feeding excess energy to the electricity grid. At night, the house can draw power from the electric grid.
The idea that houses can be built to produce as much power as they use — leaving a “net-zero” energy footprint — has drawn worldwide attention in recent years. The exact number of buildings isn’t known, but the International Energy Agency is starting to track net zero- projects around the world.
Scientists and policymakers are zeroing in on buildings — commercial and residential — because they represent the biggest end user of energy, accounting for 40 percent of U.S. energy use, more than the transportation or industrial sectors. “People are taken aback when they learn this,” Fanney says.
Buildings are also the fastest-growing sector, according to government researchers. They account for “73 percent of all the electricity used in our nation,” electricity that could be better directed elsewhere, Fanney says. “It’s important that we cut down on consumption in general, and it’s even more important as we transition to electric cars that we free up electricity from buildings.”
The goal of the National Institute of Standards and Technology is to track how the house operates for a year so that it can develop ways to measure how the equipment performs and provide information and resources that manufacturers could use to advance the technologies.
The NIST hopes “to demonstrate that net-zero energy usage can be achieved in the typical American home, not just in high-end homes or home designs that might not appeal to the typical buyer,” Fanney says. “The technologies in this net-zero energy test facility are all commercially available.”
The scientists predict that the methods and standards they develop will help spur market acceptance of new technologies. “Unless you have a metric that captures true performance, it’s very hard for the public to accept it,” Fanney says. “Most people have no clue about how the systems in their houses are performing together or how much energy their appliances are using.”
After the one-year demonstration, NIST researchers can try combinations of other energy and mechanical systems that have been built in and calculate how the house would run with more or fewer family members.
Fundamental to the design, Pettit says, is “a state-of the art enclosure system that provides superior air tightness and thermal effectiveness.” The house is insulated and sealed so tightly that “if you were on the outside trying to blow [air] in you couldn’t do it.”
The building will be wrapped on five of its six exterior sides in four inches of rigid foam insulation sheets covered in foil. Rigid insulation will also be on the basement interior walls as well as cellulose insulation — made from newspapers — in the walls and rafters. “All insulation is good. The more the merrier,” Pettit says. Intentional openings will allow for air change when needed, to dilute moisture-laden interior air with drier exterior air. When outside air is too wet, the mechanical systems will provide dehumidification. All of this helps to prevent mold growth in the home, Pettit says.
The ventilation system also is designed to ensure indoor air quality by completely replacing the interior volume of air with exterior air once every three hours. To ensure indoor air quality, the designers also chose materials and paint with little chemical off-gassing potential, Pettit says. The walls, roof, window openings and other places where materials are joined are also meant to be water tight, to prevent mold.
To ensure indoor air quality, the designers chose materials and paints with little chemical off-gassing potential and are installing “an air distribution system to bring outside air in the windows,” Pettit says. One system of ductwork is dedicated to distributing fresh air through the house; another for dehumidification and humidification.
The house is designed to meet the highest Leadership in Energy and Environmental Design certification, platinum, and to meet the Environmental Protection Agency’s Indoor airPLUS certification. Bethesda Bungalows in 2009 completed the first LEED Platinum home in Montgomery County, a $2.3 million, five-bedroom upscale bungalow near downtown Bethesda that it calls the Incredibly Green Home.
What’s not clear is how much a similar nonexperimental net-zero house would cost. The NIST facility is installing multiple redundant systems so they can be tested, and the site lacked basic services such as water, sewer and electricity, which would be available to a house built in an existing neighborhood. The $2.6 million contract “includes infrastructure that wouldn’t normally be associated with the cost of a home in a typical subdivision,” Fanney says.
Among the multiple heating and cooling systems that will eventually be tested are: advanced air-to-air heat pump units, earth-coupled heat pump systems with various ways of extracting energy from the earth, systems that move refrigerant from room to room in lieu of air-based distribution systems that require ducts, and high-velocity air ducted systems.
The scientists expect to develop a cost estimate for a regular net-zero house after the first year. Net-zero houses built so far — often in the South or West, where sunshine is plentiful — have been designed as showcases for wealthy owners, using high-end materials and finishes, the NIST design group says. Brad Beeson, Bethesda Bungalows’ green-building expert, estimates that his firm could build one for “under a million” and considerably less if the high-end finishes that clients normally request are eliminated.
Pettit’s firm recently built a 4,000-square-foot traditional Cape Cod net-zero home in Concord, Mass., for $600,000. High-end finishes, she says, can “easily add $50 to $100 a square foot” to the price.
Project participants are convinced that net-zero energy design isn’t a fad but the way to the future. “If you know anything about the limitations of our oil supplies, you know it’s the only way forward in light of the rapidly approaching energy crisis,” Beeson says. “It’s totally doable now. . . . It’s the challenge of getting the architects of the world up to speed and getting the public to understand the impact of this — why it’s more important [to spend money on energy reduction] than on getting all-stainless appliances in your house.”
Even if the United States moved toward using commercially available technology to cut energy use rather than net-zero, “it would make a huge difference,” says Jerry Therrien, president of contractor Therrien Waddell. “If you can get 70 percent of this, you’ve gone a long way.”
Fanney envisions a future when “buildings will talk to the grid, and the power plant will talk to the distribution lines.” And when houses “will have mpg stickers, like cars, showing how well they run.”