Earlier versions of this article about a house to be built on the grounds of the National Institute of Standards and Technology in Gaithersburg to test energy-saving technologies incorrectly said that the house would be built adjacent to the institute's building and fire research lab. It will be next to the engineering lab. This version has been updated.
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'Net zero' house to be built in Maryland should produce as much energy as it uses
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.