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| Air Leakage Testing |
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 It is estimated that air leakage is responsible for 5% to 40% of the cost of air conditioning in a building. Along with that realization comes several new energy code requirements, most of which deal with new residential construction.A blower door is a large fan set up in a main entry door of a building. Air is sucked out of the building until a steady pressure of -50 pascals is achieved. Although 50 pascals is a relatively small amount of pressure (enough to lift a column of water about one-tenth of an inch), the results can be surprising. Air can be felt flowing into the building through recessed lights, fireplaces, attic stairs, doors, windows, plumbing penetrations, dropped ceilings, unsealed wall cavities, and air conditioning registers. The blower door test helps easily locate the leaks so they can be sealed. The blower door shows the air flow rate in cubic feet of per minute (cfm) at -50 pascals (cfm50), which, if you know the volume of air in a building, can be converted into air changes per hour at -50 pascals (ACH50). The blower door test can also be used to estimate a building's natural air leakage rate. The natural air leakage rate is the leakage you can expect under normal everyday conditions. The blower door test results are divided by what is know as an n-factor, a number calculated by the Lawrence Berkeley National Laboratory for regional zones across the country. This gives the estimated natural air leakage rate. The natural air leakage rate can also be measured using tracer gas, although this method is much less common. A tracer gas is released into the building and its dilution is measured over time, giving an indication of the building's natural ventilation rate. The duct blaster is a smaller fan set up to blow air into the air conditioning duct system. The fan is set up to blow into a return register. All other registers are taped off. The fan is turned on and the air flowing into the ducts is measured at a steady state of 25 pascals. The duct leakage just to the outdoors can be measured by using the blower door in conjunction with the duct blaster, to equalize the pressure inside the building. As for new code requirements, the 2009 International Energy Conservation Code (IECC) requires whole-building air tightness to be demonstrated by either a blower door test showing less than 7 air changes per hour at -50 pascals of pressure (ACH50), or by third-party field inspection according to a prescribed checklist. Air conditioning duct leakage to the outdoors must be less than or equal to 8 cubic feet per minute (cfm) per 100 square feet of conditioned floor area, and total duct leakage (outdoors and indoors) must be less than or equal to 12 cfm per 100 square feet of conditioned floor area. The City of Houston has also adopted new air leakage testing requirements. Effective October 1, 2009, all new residential buildings in Houston must achieve 15% above the energy code standards. This can be demonstrated using software such as IC3, RESCheckTM, Energy Gauge or REM/Rate software together with a duct-blaster and blower-door test at the time of final inspection. Compliance can also be demonstrated by complying with one of a list of prescriptive approaches, several of which involve duct and/or whole building air leakage testing. Whole-building air tightness must be demonstrated by a blower door test showing less than 0.35 ACHn. Air conditioning duct leakage to the outdoors must be generally less than 10%. For more information on the City of Houston's 15% above energy code requirements, see the Houston Residential Energy Code. |
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Three Texas Locations
League City, TX (Galveston)
2951 Marina Bay Dr. #130-356
League City, TX 77573
Pasadena, TX (Houston)
3910 Fairmont Parkway #272
Pasadena, TX 77504
Beaumont, TX
2204 Oak North
Nederland, TX 77627