A TRANSIENT HEAT AND MASS-TRANSFER MODEL OF RESIDENTIAL ATTICS USED TO SIMULATE RADIANT BARRIER RETROFITS, PART I - DEVELOPMENT

This paper describes a transient heat and mass transfer model of resid ential attics. The model is used to predict hourly ceiling heat gain/l oss in residences with the purpose of estimating reductions in cooling and heating loads produced by radiant barriers. The model accounts fo r transient conduction, convection, and radiation and incorporates moi sture and air transport across the attic, Environmental variables, suc h as solar loads on enter attic surfaces and sky temperatures, are als o estimated. The model is driven by hourly weather data which include: outdoor dry bulb air temperature, horizontal solar and sky radiation, Ll,ind speed and direction, relative humidity (or dew point), and clo ud cover data. The output of the model includes ceiling heat fluxes, i nner and outer hear fluxes front all surfaces, inner and enter surface temperatures, and attic dry bulb air temperatures, The calculated flu xes have been compared to experimental data of side-by-side testing of attics retrofit with radiant barriers. The model predicts ceiling hea t flows with an error of less than ten percent for most cases.