Retrotec Residential Pressure & Air Leakage - Manual (Page 32)

Page 32 of 75
©Retrotec Inc. 2014
1. Open vents, doors, or windows from the unconditioned spaces to the outdoors.
2. Perform a zone test on the unconditioned spaces, with the Blower Door on.
3. If the house to unconditioned space pressure difference is equal (or nearly equal) to the pressure
difference between the house and outdoors, then there is nothing to worry about.
4. If the pressure difference does not equal the pressure difference between the house and outdoors,
and the variance is more than 5 Pa, then the measured duct leakage to outside will be artificially
low.
Figure 10: Zonal pressures in a home's unconditioned spaces.
In the picture in Figure 10, all displayed pressures are relative to the outdoors. The house is pressurized to 50
Pa. The unconditioned garage is open to the outdoors and has no pressure difference. The unconditioned attic,
however, does not open to the outdoors, and displays a 10 Pa relative to the outdoors. Duct leaks in the attic,
therefore, will not be fully reflected in the measurements made in any of the procedures as described above.
4.2.4. Create a leakage map of the duct system with a Pressure Pan test on each
register
A pressure pan can be used to locate Duct Leakage to the Outdoors with a Blower Door. With the building
pressurized to 50 Pa, a pressure pan can be placed over each register to take a measurement of the pressure
between the duct and the room where the register is located. The larger the pressure difference, the larger the
leak(s) in the nearby ducts. A general leakage map of the duct systems can be made by testing each register in
the building. This method can also be used after duct repairs, to determine if all major leakage sites have been
fixed.
A measurement of 50 Pa would indicate a complete disconnect of the duct system, because it indicates there is
pressure difference between the house and the duct which is the same as the pressure difference between
house and outdoors. Typically, a pressure pan will have a reading of 0 to - 20 Pa when the house is
depressurized to -50 Pa. Higher readings indicate a higher degree of connectivity to the outdoors than to the
50 Pa
10 Pa
0 Pa