Welcome to Net-Zero
ASTM Standards Play Current and Future Role in Energy-Efficient Housing
For most people (and for most homes) the likelihood of going through a whole year spending next to nothing on energy is a goal that seems far out of reach.
In fact, it is only relatively recently that insulation technologies, coupled with cutting-edge renewable energy tools, have made the concept of a net-zero energy use home anything more than a pipe dream.
However, thanks to a program at the National Institute of Standards and Technology, the technology is moving ahead by leaps and bounds. And the proof of concept is part of the Maryland landscape now with the construction and successful operation of the Institute's Net-Zero Energy Residential Test Facility, or NZERTF. Indeed, in its first year of operation, despite an unusually harsh winter, NZERTF managed to come out ahead on its energy budget, saving thousands of dollars on its electric bill and generating kilowatt hours to spare, which were exported back to the power grid.
The two-story, four-bedroom, three-bath house, inhabited for now only by a "virtual" family rather than by actual humans, is designed to fit in with its suburban environment and to be 60 percent more energy efficient than typical houses, meeting the requirements of the 2012 version of the International Energy Conservation Code, which Maryland has adopted.
The 2,700 square-foot (252 square-meter) test house was built to conform to U.S. Green Building Council LEED Platinum standards - the highest standard for sustainable structures, with R45 rather than R20 rated exterior walls and an R75 roof, rather than a more typical R30-35. (R values are measures of thermal resistance.)
Another novel departure is the inclusion of all duct work within the envelope of the inhabited area - reducing losses of warm or cool air. Its other key components, in addition to energy-efficient construction, include extra efficient appliances, as well as energy-generating technologies, such as solar water heating and a solar photovoltaic system.
A. Hunter Fanney, chief of the Energy and Environment Division within NIST's Engineering Laboratory, Gaithersburg, Maryland, explains that the house has two goals: in the short term, to demonstrate net-zero energy use in a house similar to other homes in the community, and longer term, to provide a test bed to enable improvement of test methods and performance metrics for building energy efficiency and renewable energy technologies.
Most current equipment test procedures are based on procedures within the ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) community. ASTM standards have also played a crucial role, including:
- E741, Test Method for Determining Air Change in a Single Zone by Means of a Tracer Gas Dilution;
- E779, Test Method for Determining Air Leakage Rate by Fan Pressurization;
- E917, Practice for Measuring Life-Cycle Costs of Buildings and Building Systems;
- E964, Practice for Measuring Benefit-to-Cost and Savings-to-Investment Ratios for Buildings and Building Systems;
- E1057, Practice for Measuring Internal Rate of Return and Adjusted Internal Rate of Return for Investments in Buildings and Building Systems;
- E1074, Practice for Measuring Net Benefits and Net Savings for Investments in Buildings and Building Systems; and
- D1598, Test Method for Time-to-Failure of Plastic Pipe Under Constant Internal Pressure.
Fanney says that NIST representatives are currently involved with ASTM Committee E44 on Solar, Geothermal and Other Alternative Energy Sources, which was formed in 1978. "Through the work of the E44.09 Photovoltaic Electric Power Conversion subcommittee, we hope to develop better ways of measuring and predicting the performance of solar photovoltaic modules," he says.
NIST is also active on Subcommittee E06.41 on Air Leakage and Ventilation Performance, which is responsible for standards for measuring building airtightness and air change rates. In addition, Subcommittee D22.05 on Indoor Air covers standards related to contaminant emissions from building materials and furnishings, as well as other factors affecting indoor environmental quality.
The economic performance of the house is based on a suite of standards produced by ASTM's Subcommittee E06.81 on Building Economics. NIST representatives helped create that subcommittee in 1979 and have maintained various leadership roles in it ever since, he notes.
Indeed, standards development is critical to implementing new technologies and measuring successes, says Fanney. The ongoing measurement-related work at the NZERTF is expected to help make energy efficient technologies more affordable and will identify the most cost-effective means for reducing energy consumption.
In the longer term, NIST believes the development of tests and standards for building energy efficiency technologies and environmental performance will provide much needed information to builders, home buyers, regulators and others.
NIST estimates that incorporating all of the NZERTF's energy-related technologies and efficiency-enhancing construction improvements currently adds about $160,000 to the price of the home if built to local building codes. In terms of livability, the actual structure of NZERTF is not unusual, according to David Catt, a student sponsored this year by ASTM as part of the Washington Internships for Students of Engineering (WISE) program, who recently visited the facility. "NIST purposely designed the home to be similar to other homes of similar size in the area and sacrificed certain energy-saving techniques, such as fewer windows and shades over windows, to create a home that people would actually be willing to inhabit," says Catt.
"I think this makes a lot of sense because, otherwise, the data produced wouldn't really be applicable to market building norms and consumer tastes that are much more influential in housing choices," Catt says.
And net-zero buildings are coming - soon. Some jurisdictions are already moving to mandate the construction techniques, says Fanney. If history is any indication, standard and code developing organizations will be there to develop the technical underpinnings of the new energy efficiency.Alan Earls is a writer and author who covers business and technology topics for newspapers, magazines and websites. He is based near Boston, Mass.