2- Point Blower Door Test CFM 25 and CFM 50 Typical blower door test assumes.65 coefficient “N” “N” must be between.5 and.75 for accurate test Formula: “N” = (LN Q50/Q25) / (LN 50 Pa /25Pa) “Q” is flow “LN” is Log Normal

2- Point Blower Door Test Test House at both CFM 25 and CFM 50 Formula: “N” = (LN Q50/Q25) / (LN 50 Pa /25Pa) “N” must be between.5 and.75 for accurate test Provides additional valuable information Typical blower door test assumes.65 coefficient “N” A value below.65 suggests large holes A value above.65 suggests smaller holes

2- Point Blower Door Test Example “N” = (LN Q50/Q25) / (LN 50 Pa /25Pa) Example test results CFM 50 = 2,139 CFM 25 = 1,367 “N” = (LN of CFM 50/CFM 25) divided by (LN of 50 Pa / 25Pa) 2,139 divided by 1,367) = divided by 25 = 2 LN of 1.56 =.44 LN of 2 = divided by.693 =.64 “N” for this example is.64 “N” for this example is.64