Abstract
A residential ducted forced-air heating system was investigated to assess the impact of duct system leakage. Ductwork pressurisation and tracer gas techniques were used to quantify leakage in the heating duct system, and added infiltration to the house caused by duct leaks. Determination of leakage fraction by pressurisation tests showed a distribution loss of 23% in supply ductwork and 3% for the return duct during normal operation of the air heater's circulation fan. Tracer gas tests showed that the house infiltration is affected by the duct system leakage: infiltration increased from 0.1 ac h-1 for no ducting, to 0.21 and 0.5 ac h-1 with heating ductwork when the circulation fan is off and on respectively. A direct calculation shows the heat loss due to duct leakage to be about 45% of the house peak winter load. Hourly simulation of the space heating requirements indicates an annual increase of 35% in heating load due to heating duct leakage and transmission losses.
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