Thermal response of basement wall systems with low-emissivity material and furred airspace

Abstract

In basement wall systems, airspaces can contribute in obtaining a higher thermal resistance, if a low-emissivity material such as reflective foil is installed within a furred-airspace. In this study, numerical simulations were conducted using the hygrothermal model ‘hygIRC-C’ that was developed at the National Research Council of Canada’s Institute for Research in Construction to investigate the steady-state and transient thermal performance of basement wall systems. This model solves simultaneously the energy equation in the various material layers, surface-to-surface radiation equation in the furred-airspace assembly, Navier–Stokes equation for the airspace, and Darcy and Brinkman equations for the porous material layers. The wall systems used in the simulations incorporate a low-emissivity material (foil with emissivity = 0.04) bonded to a moulded/expanded polystyrene foam that is installed in a furred-airspace assembly. The furring is installed horizontally and covered with a gypsum board. The structural element of the wall (external layer) is a poured-in-place concrete. Walls with and without furred-airspace assembly were considered in this study. Also, consideration was given to investigate the effect of the above-grade and below-grade portions of the wall on the thermal performance when these walls are subjected to two different Canadian climates. Results showed that at steady-state condition, the effective thermal resistance (R-value) of the wall with a furred-airspace assembly depends on the soil, outdoor, and indoor temperatures. Additionally, these wall configurations resulted in an energy savings of ~17% compared to walls without furred-airspace assembly when these walls are subjected to two different climate conditions.