Glossary

ACH50: The Air Changes Per Hour at 50 Pascals is the index used in most blower door testing. As with HERS scores, a lower score is more efficient, indicating more air-tightness.
 
BTU (British Thermal Unit): A unit used to measure quantity of heat defined as the quantity of energy necessary to raise the temperature of 1 lb. of water 1o Fahrenheit.
 
BLOWER DOOR TEST: This tool helps determine the air-tightness of new and existing homes using a fan to maintain a pre-set level of depressurization in the structure.
 
BUILDING ENVELOPE: The assembly of exterior partitions of a building that enclose conditioned spaces, through which energy may be transferred to or from the exterior, unconditioned spaces, or the ground.
 
BUILDING INSPECTOR: An employee of. local or state government building department whose responsibilities reviewing building plans and/or inspecting building sites to determine whether or not they meet existing health, safety, and/or energy codes.
 
CONDITIONED AREA/SPACE: That portion of the building that is heated and/or cooled.
 
HERS (Home Energy Rating System): This RESNET Home Energy Rating System scores homes against an index of the average U.S. new home’s energy efficiency HERS of 100. The lower the score, the more energy efficient the home.
 
HPR (The Home Performance Report): An easy-to-understand document that serves as the energy “window sticker” for a home, allowing home buyers to compare home energy scores in the same manner as they compare miles-per-gallon information when they buy a new car.
 
INFULTRATION: The uncontrolled inward leakage of air through cracks and gaps in the building envelope, especially around windows and doors.
 
R-VALUE: A unit of thermal resistance used for comparing insulating values of different materials. The higher the R-Value of a material, the greater its insulating properties and the slower the heat flows through it.
 
RESNET: Residential Energy Services Network is an independent, non-profit organization that sets national standards for energy ratings, ensuring accuracy and consistency.
 
RESNET RATERS: Certified professionals conduct on-site inspections and energy tests, including a final blower door test at a new home’s completion.
 
THERMAL ENVELOPE: The building's exterior shell - walls, foundation, floors, ceiling, windows, doors, and roof.
 
UNCONDITIONED SPACE: A space that is neither directly nor indirectly conditioned space, which can be isolated from conditioned space by partitions and/or closeable doors.