Name: Module 6 - Blower Door Testing
Author: Andy Cockburn

Terminology & Calculations

These terms, acronyms and abbreviations are used in energy advising and blower door testing:

Term	Definition
ACH₅₀	Air Changes per Hour @ 50 Pa
CFM	Cubic feet per minute - air flow rate
CFM₅₀	Standard airflow rating for blower door tests
CFM_natural	Natural airflow in cubic feet per minute
50 Pa	50 Pascals - measure of air pressure
Pascal	Metric measure of air pressure
CRF	Cannot Reach Fifty (Pascals)
N-factor	Estimate for naturally occurring leakage (usually around 20)
EqLA	Equivalent Leakage Area Defined by Canadian National Research Council as the area of a sharp edged orifice (a sharp, round hole cut in a thin plate) that would leak the same amount of air as the building does at a pressure of 10 Pascals.

To calculate ACH =

Reading of CFM₅₀ from manometer x 60 minutes / house volume

Example:

Reading of 3550 CFM₅₀ on machine
3550 x 60 minutes = 213,000
House is a ranch style 48' x 32' with 8' walls (no basement) = 12,288 cubic feet
213,000 / 12,288 = 17 ACH

To calculate EqLA (in sq. inches) =

Reading of CFM₅₀ from manometer / 10 (Pascals)

Example: