THE ENERGY IMPACT OF AIR LEAKAGE THROUGH INSULATED WALLS

Infiltration is customarily assumed to increase the heating and coolin g load of a building by an amount equal to the mass flow rare of the i nfiltration times the enthalpy difference between the inside and outsi de air-with the latent portion of the enthalpy difference sometimes ne glected Art experimental and analytical investigation has been conduct ed on the actual energy impact of air leakage on a well-characterized insulated stud-cavity wall specimen. Calorimetric measurements conduct ed on the specimen with measured amounts of air leakage introduced und er a variety of controlled conditions and configurations verify earlie r rest cell measurements showing that infiltration heat exchange cart lead to a much smaller change in the energy load due to infiltration t han is customarily calculated and show the dependence of infiltration heat exchange on pow rate and path length. An analytical model based o n fundamental heat and mass transfer principles has been developed and the predicted values of infiltration Hear Exchange Effectiveness, eps ilon, as a function of airflow rates and effective path length for fiv e stud-cavity wall specimen test configurations were consistent with t he experimental results. Significant experimental results include: (i) epsilon values in the 0.16-0.7 range in the stud-cavity and (ii) epsi lon values of 0.16 to 0.34 for air exiting the stud-cavity directly ac ross from the entry. These results indicate that significant heat reco very is probable for most leakage occurring through insulated stud cav ities.