How much duct leakage is acceptable?

According to building energy efficiency standards and modern residential HVAC installation codes, acceptable duct leakage to the outside or unconditioned spaces should generally not exceed ten percent of the total fan flow rate, with total leakage tested via a duct pressurization blower door test ideally falling under six percent. Excessive duct leakage forces your heating and cooling system to work significantly harder to condition your home, leading to soaring utility bills, uneven room temperatures, and poor indoor air quality as dust and insulation fibers are pulled into the airstream. While older homes often suffer from twenty to thirty percent duct leakage due to unsealed joints, sealing and insulating ductwork drastically improves efficiency. You can troubleshoot high energy bills with a professional duct test. You can verify compliance when diagnostic pressure tests confirm total leakage rates meet local building code standards.