Comparison of Methods for the Measurement of Air Change Rates and Interzonal Airflows in Two Test Residences

Abstract

Four different but complementary methods—the tracer gas dilution method, single-tracer constant concentration, passive perfluorocarbon tracers (constant release), and constant release of multiple halocarbon tracers with semicontinuous analysis—were used to obtain detailed information on air exchange and interzonal airflow rates in the two GEOMET bilevel research houses. The four methods yielded comparable measurements of single-zone (whole-house) air exchange rates. Constant concentration tracer gas, perfluorocarbon tracer, and multiple halocarbon tracer measurements yielded comparable measurements of upstairs and downstairs air infiltration rates; downstairs infiltration rates were as much as seven times higher than upstairs. The constant-concentration method also provided detailed information on room-specific infiltration rates. Perfluorocarbon tracer (PFT) measurements of airflow rates between conditioned zones, the attic, and garage demonstrated the effectiveness of house-tightening retrofit procedures to reduce airflows to the unconditioned airspaces. Perfluorocarbon and halocarbon measurements of week-long, time-averaged interzonal airflow rates were comparable, but the halocarbon system showed that hourly interzonal airflow rates could be as much as an order of magnitude higher than the week-long average.