ACH50n

ACH50n is a unit of measurement used to quantify air leakage in buildings. It represents the air change rate per hour at a specific pressure difference, typically 50 Pascals. This pressure difference is achieved by using a powerful fan to either pressurize or depressurize the building. The volume of air required to maintain this pressure difference is then measured. This measurement, when divided by the building's volume, gives the ACH50n value. A lower ACH50n value indicates a more airtight building, while a higher value suggests greater air leakage. Building codes and energy efficiency standards often specify maximum allowable ACH50n values to ensure buildings are adequately sealed, reducing energy consumption for heating and cooling and improving indoor air quality by controlling uncontrolled infiltration. ACH50n is a key metric in blower door testing, a standard procedure for assessing building airtightness.