Data from two research houses built over basements, one in Chicago, and the other in Bowie, Maryland, were analysed to evaluate the effectiveness of their ducted forced-air distribution systems. Two approaches were used, (1) comparison of air infiltration rates during heating periods with ducted systems against periods with unducted systems, and hours of cooling with continuous blower operation against hours without blower operation, and (2) a mass and energy balance on the forced-air distribution system to disaggregate energy losses due to air leakage from the ducts and heat conduction. The Chicago duct system is neither taped or insulated whereas the Bowie house was both taped and insulated.

KEYWORDS: warm air heating, housing, domestic, air conditioning, ducts, air infiltration, leaking, thermal insulation, experiment, air distribution, USA.