Performance testing of new homes: a powerful set of tools for builders
By Richard Stone, Extension Educator in Housing Technology
If you are considering "green building" certification of the homes you build, you may have checked out some of the programs to learn more about the process. Third party verification and performance testing are common elements of certification programs in the local market. Certification as an Energy Star Qualified New Home documents the performance and features of a new home based on standardized test protocols and is a prerequisite of both LEED for Homes and Minnesota GreenStar.
Uniform testing and computer modeling also provides the Home Energy Rating System® (HERS) index number which projects the home's energy use. Testing must be done by a rater who has completed approved training and passed a nationally based test to achieve professional certification. Raters may also hold advanced certifications and provide additional services including testing and verification for tax credit documentation and the required verifications for green building and energy programs. Specialized tools are used by raters as they measure and document the performance of new homes. The information collected by the rater during the testing process provides a valuable snapshot of the home. Some builders like to be present for the testing process so they can ask questions and learn more about the homes first-hand. Because the tools in a rater's toolbox seem pretty high-tech, builders may not be familiar with the equipment or the testing process.
A blower door is used to test air leakage of the building envelope by depressurizing the home following a standardized method. The test calculates the amount of air infiltration by measuring pressure differences across the exterior walls. Air leakage through the building envelope impacts energy costs, occupant health, and building durability. Homes that allow air movement across the building envelope waste energy during both the heating and cooling seasons. Air transported moisture that becomes trapped within building assemblies and is unable to dry can lead to health concerns for homeowners and shorten the life of a structure.
Infra-red thermography shows surface temperature differences and is used to review the thermal performance of insulation. It can also be used in combination with the blower door to locate air leakage through the building envelope. Air movement through a building assembly changes surface temperatures in distinctive ways that can be interpreted by the rater to identify unsealed framing gaps, holes for mechanicals, and other sources of infiltration. Because evaporation causes cooling, water leaks are occasionally discovered by the rater during the review of a home. Builders provided with this kind of information have the opportunity to zero in on the specific areas where they can improve the energy performance of a home or prevent callbacks.
Energy efficiency and comfort can be compromised by leaky ductwork in homes because heated or cooled air is not delivered where it is needed. Ducts should be sealed at all joints and seams. Air distribution systems are tested by the rater using a duct blaster to determine air tightness. Sealing of all ductwork that runs outside of conditioned (heated or cooled) space is even more critical because leakage of supply or return ducts in attics and walls may contribute to health and durability issues. Properly sized and installed systems make homes more healthy, comfortable, durable, and energy efficient.
Ventilation of the conditioned (living) space is important to control moisture, odors, and pollutants which could impact the occupants of the home. The ventilation equipment should be properly sized for each home to provide the required ventilation flows. The rater uses a balometer (flow hood) to measure the actual air flow of ventilation equipment and confirm that design goals were achieved.
In addition to providing the required verifications for energy and green building programs, each of these testing procedures provides valuable information to the home builder. Computer modeling and testing are powerful tools that allow a builder to set performance goals and then verify outcomes. Builders who take full advantage of these tools can use the information they gain from modeling and testing to better understand how their homes work, take more control of their building processes, and continually improve performance. Third party testing of each home also provides an added value that can be sold to today's informed homebuyer who is looking for proven energy efficiency in an environmentally friendly new home.