Related Resources: fluid flow

Air Leakage Rates for Typical Home Components

Fluid Engineering and Design

Air Leakage Rates for Typical Home Components

Fan pressurization measures a building’s leakage behavior that ideally varies little with time and weather conditions. In reality, unless wind and temperature differences during the measurement period are sufficiently mild, pressure differences induced by weather during the blower door test cause measurement errors.

ASHRAE Standard 62.2 establishes air leakage performance levels for residential buildings. These levels are in terms of effective annual average infiltration rate Qinf , which is based on normalized leakage area NL:

NL = 0.1 ( ELA / Afloor ) · ( H / Hr )0.4


NL = normalized leakage
Hr = reference height, ft
H = vertical distance from lowest above-grade floor to highest ceiling, ft
ELA = Effective Leakage Area (see Table 1.0)

ELA = (Lpress - Ldepress)/2

If using 0.0006 psi reference pressure:
Lpress = leakage area from pressurization, ft2
Ldepress = leakage area from depressurization, ft2

Table 1.0 Rate of Leakage ELA

Exterior Airflow Paths
ELA at
0.016 in.
of water
(0.000578 psi)
Living space envelope
Exterior wall
0.002 in2/ft2
Ceiling wall interface
0.038 in2/ft2
Floor wall interface
0.059 in2/ft
Window #1
0.78 in2
Window #2
0.30 in2
Corner interface
0.038 in2/ft
Exterior doors
2.90 in2
Living space floor to belly
0.053 in2/ft2
Interior airflow paths
Interior walls
0.029 in2/ft2
Bedroom doorframe
6.36 in2
Open interior doors
6.5 by 3 ft
Bathroom doorframe
5.12 in2
Interior doorframe
3.88 in2
Closet doorframe
0.71 in2
Attic floor
0.029 in2/ft2
Roof vents
1.45 ft2
Eave vents
5.0 in2/ft
Crawlspace and belly
Exterior walls of crawlspace
0.36 in2/ft2
Rear crawlspace vents
50 in2
Front crawlspace vents
72 in2
Crawlspace access door
32 in2
Crawlspace to belly
40 in2
Duct leak into belly
5 in2

1 in of water = 0.03613 psi
1 psi = 27.67990 In of water

Schematic of Ventilation System and Envelope Leakage
Schematic of Ventilation System and Envelope Leakage

The fan pressurization procedure discussed in the section on Envelope Leakage Measurement allows whole-building air leakage to be measured. The location and size of individual openings in building envelopes are extremely important because they influence the air infiltration rate of a building as well as the envelope’s heat and moisture transfer characteristics. Additional test procedures for pressure-testing individual building components such as windows, walls, and doors are discussed in ASTM Standards E283 and E783 for laboratory and field tests, respectively.



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  • OSHA Standard 1910.106