TRANSIENT CONDUCTIVE, RADIATIVE HEAT-TRANSFER COUPLED WITH MOISTURE TRANSPORT IN ATTIC INSULATIONS

A transient, one-dimensional thermal model that incorporates combined conduction, radiation heat transfer, and moisture transport for reside ntial attic insulations has been developed. The governing equations ar e the energy equation, the radiative transport equation for volumetric radiation within the insulation batt, and the species equations for b ound H2O and vapor H2O. A simultaneous solution procedure with a Euler ian control volume-based finite difference method was used to solve th e energy equation and the species equations. The method of discrete or dinates was used in solving the radiative transport equation. For H2O transport, both diffusion of vapor H2O and bound H2O, and moisture ads orption/desorption within the insulation binder are included in the mo del. The experimental data measured at an occupied North Mississippi r esidence for R19STD (standard R19 fiberglass insulation batt without a foil radiant barrier) were used to validate the model which predicted heat fluxes for summer, spring, winter, and fall seasonal conditions. These predictions were compared with the measured heat nux data and t he predictions from the dry model (without the moisture transport). Va rious profiles such as temperature-time histories, relative humidity t ime histories, spatial H2O concentrations, spatial temperatures, and s patial heat fluxes are presented to explain the overall heat transfer behavior.