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Professional energy auditors use qualitative and quantitative testing to help measure the amount of duct leakage in air distribution systems. In a typical house about 20 percent of the air that moves through the duct system is lost due to leaks, holes, and poorly connected ducts. How It Works A Pressure Pan is a rectangular pan with a pressure tap that allows it to connect to a pressure gauge. Used in conjunction with a Blower Door , it is a very useful tool for targeting which ducts are most in need of being sealed. - The home is depressurized to -50 Pascal (with respect to outside) with the Blower Door.
- The technician holds the pressure pan over a single duct register to get a pressure reading in that particular duct run.
- If the duct run is excessively leaky or partially disconnected, the pressure will vary considerably from the rest of the house (more than -5 Pa with respect to the house).
To measure duct leaks more accurately, the technician may use a Duct Blaster. A Duct Blaster is a smaller version of the blower door, also consisting of a variable-speed fan and a pressure gauge. All supply and return registers are taped close, the Duct Blaster is connected to the air handler to pressurize the system to +25 Pa, and the total amount of duct leakage is determined. Since some duct leakage usually occurs within the conditioned space and is not necessarily bad from an energy standpoint, the Duct Blaster may be used in conjunction with a blower door to measure duct leakage to outside. - All duct registers are taped close and the home is pressurized to +25 Pascal (with respect to outside) with the Blower Door.
- The Duct Blaster is connected to the air handler (or large return register) to pressurize the system to +25 Pa (or 0 Pa with respect to the house).
- All duct leakage measured is to the outside, or unconditioned space, and represents the heating or cooling energy lost.
Images are Copyright ©1999-2007 The Energy Conservatory. |
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Professional energy auditors may use thermography—or infrared scanning—to detect heat losses and air leakage in building envelopes. How It Works Thermography measures surface temperatures by using infrared cameras. This thermal imaging camera sees light that is in the heat spectrum. Images on the film record the temperature variations of the building's skin, ranging from white for warm regions to black for cooler areas. The resulting images help the auditor determine whether insulation is needed. They also serve as a quality control tool, to ensure that insulation has been installed correctly. Thermographic scans are also commonly used with a blower door test running. The blower door helps exaggerate air leaking through defects in the building shell. Such air leaks appear as black streaks (in winter, white streaks in summer) in the infrared camera's viewfinder. Infrared scanning allows energy auditors to check the effectiveness of insulation in a building's construction. The resulting thermograms help auditors determine whether a building needs insulation and where in the building it should go. Because wet insulation conducts heat faster than dry insulation, thermographic scans of roofs can often detect roof leaks. The most accurate thermographic images usually occur when there is a large temperature difference (at least 20°F [14°C]) between inside and outside air temperatures. In northern states, thermographic scans are generally done in the winter. In southern states, however, scans are usually conducted during warm weather with the air conditioner on. In mixed climates, scans can be performed during both the heating and cooling seasons. Images Copyright © FLIR Systems |
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