Thermal Effects of Adding a Balcony to a Wood Stud Wall Assembly

Improving the thermal performance of buildings is an essential element when addressing issues related to the effects of climate change on the building envelope. Minimizing energy usage of and heat losses from buildings are important measures in achieving these associated goals. It is recognized that the majority of the heating and cooling demand is caused by thermal transmittance through wall assemblies. Hence, characterizing the thermal performance of wall assemblies is a vital part of the design process to help ensure heating and cooling systems have been properly sized. In this context, it is generally recognized that thermal bridging can affect the overall thermal performance of wall assemblies. In this study, the thermal bridging effect of a balcony slab edge was investigated both experimentally and numerically. A 2.4 m × 2.4 m wood-stud wall assembly, typical of North American wood-frame construction practice, was fabricated with an opening to accommodate a slab edge. The openings in the wall assemblies were first filled with EPS and thereafter tested in the guarded hot box; following which, the EPS in the respective wall assembly, was replaced either with a slab edge. COMSOL Multiphysics was employed to model the heat transfer across the wall assemblies using a three dimensional simulation configuration of the walls. The use of a three dimensional configuration of the wall assemblies was considered critical to completing the investigation, given that lateral heat transfer is a highly significant component when considering how thermal bridging affects the overall thermal transmittance through the wall. The numerical results were benchmarked against results obtained experimentally from completion of standard guarded hotbox tests. The results were used to study the reduction in thermal resistance for each case.