Parameters affecting air infiltration and air tightness in 31 east Tennessee homes.

A major pathway for loss of conditioned air in east Tennessee homes with externally located HVAC systems is leakage in the ductwork. The effect on infiltration rates, as measured by Freon-12 tracer gas dilution, becomes marked if the central duct fan is operating. Duct fan on and duct fan off measurements of the rate of air exchange gave mean values of 0.41 and 0.78 ach respectively in a total of 31 homes. Specific leakage areas measured using a pressurization technique are affected to a lesser extent by inclusion of the ductwork volume within the total volume of the house being pressurized. A subset of 7 of the study homes were measured using this technique - the average increment in the specific leakage area was 15%.