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 Q_inf , which is based on normalized leakage area NL:

NL = 0.1 ( ELA / A_floor ) · ( H / H_r )^0.4

Where:

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 = (L_press - L_depress)/2

If using 0.0006 psi reference pressure:
L_press = leakage area from pressurization, ft²
L_depress = leakage area from depressurization, ft²

Table 1.0 Rate of Leakage ELA

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

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.

Related:

• Ventilation Duct Stack Pressure Review, Formulas and Calculator
• Overall Heat Leakage Coefficient Equation and Calculator
• Mass Flow Rate Fluids Flow Equation
• Fluid Volumetric Flow Rate Equation
• Siphon Flow and Discharge Rates

References