ACH50

Metrics and Efficiency Ratings - Home Energy and Building Envelope pillar

Also known as: air changes per hour at 50 Pa

Air Changes per Hour at 50 Pascals. The blower door test result expressed as how many times the home's air volume turns over per hour under 50 Pa depressurization.

ACH50 is the most common way to report blower door test results. It expresses leakage as the multiple of the home's volume that passes through the envelope per hour at 50 Pa pressure. Lower is tighter. Reference points: pre-1990 Ontario house typically 4-8 ACH50; current OBC new build target around 3 ACH50; ENERGY STAR for New Homes under 2.5 ACH50; R-2000 under 1.5 ACH50; Passive House under 0.6 ACH50. Save on Energy HRS rebates require a pre and post test.

See the full Ontario HVAC and home energy glossary or browse the Home Energy and Building Envelope pillar.