Thermal performance impacts of vented EIFS assemblies in the cold climate of Southern Ontario

Abstract

One of the key improvements in EIFS/ETICS is the addition of geometrically-defined drainage cavities at the rear of the continuous insulation layer to allow water that has penetrated the outer EIFS lamina to drain out by gravity to the exterior; and to provide an opportunity for enhancing the convective drying ability of the wall assembly by introducing air flow and moisture exchange between the cavities and the exterior environment. EIFS assemblies with such cavities can be either vented or ventilated depending on the vents size, location and distribution. The integration of these cavities has raised questions regarding their impacts on the thermal performance of wall assemblies constructed of EIFS with such cavities. The principal objective of this research was to evaluate the reduction in the whole-assembly's effective thermal resistance due to the use of vented EIFS in lieu of face-sealed EIFS. Thermal numerical simulations were conducted on models that were validated against experimental results of full-scale field tests conducted in the cold climate of southern Ontario. Reductions in the thermal resistances of vented EIFS assemblies were observed in the range of 1.4–5.3% and 0.1–4.6% for south and north facing walls, respectively. Reducing the spacing between the cavities further reduced the thermal resistances due to increased ventilation. It was also found that the thermal resistances of the lightly and medium insulated south-facing EIFS were lower than their northern counterparts, mainly due to the thermal storage ability of the construction materials. However, heavily insulated EIFS reduces this flux of heat and eventually the south-facing walls' thermal resistances overcome their northern counterparts.