Engineering firm Morrison Hershfield and Schöck have issued a comprehensive report on the impact of concrete balconies on thermal and whole building energy performance. The report, which analyzes the potential impact that structural thermal breaks have in reducing the overall heating energy consumption and raising interior surface temperatures, shows structural thermal breaks can reduce overall heating energy consumption from 7 to 14 per cent and raise interior surface temperatures by roughly 7ºC, versus conventional concrete slabs. The complete Morrison Hershfield report, “Thermal and Whole Building Energy Performance of Thermal Break Technology for Concrete Balconies in High-Rise Multi-unit Residential Buildings” is available at http://www.schoeck.ca/MHreport.
“This study is timely and relevant to high-rise residential buildings in cold climates and jurisdictions where industry is adjusting to more stringent energy standards but is looking to minimize costs, minimize changes to construction methods and limit constraints on architecture. The report provides guidance regarding questions that builders and designers are asking about the impact of thermal breaks for cantilevered balconies.” said Patrick Roppel, Building Science Specialist from Morrison Hershfield.
MH utilized a whole building energy model, Energy Plus, to analyze a common multi-unit residential high-rise building — a 32-floor, 422-unit structure, with 356,608 square feet of floor area, 163,321 square feet of wall area with roughly 40 per cent “vision glass” (windows, glass doors), and 3.5 per cent of exposed cantilevered concrete slab area (balconies).
The study analyzed the impact of thermal bridging (energy loss, condensation risk and thermal comfort) regularly caused by penetrating a building envelope with a balcony slab, for three concrete balcony scenarios:
- Conventional solution–Cantilevered concrete balcony with continuous concrete slab penetrating through the building envelope.
- Site solution–Cantilevered concrete balcony slab with intermittent insulation placed between continuous concrete beam connections.
- Schöck solution–Cantilevered concrete balcony with an Isokorb CM20 thermal break.
The study reports that “a principal benefit of the Schöck solution is that the floor is much warmer in the winter than with the other construction methods. The floor slab at the perimeter is warmer, thus providing benefits for condensation resistance and thermal comfort, and the heat loss through the balcony area is greatly reduced.”
From a whole building perspective, the Schöck solution reduced overall heating energy consumption from 7 per cent to as high as 14 per cent when using Isokorb in conjunction with higher performance assemblies compared to a building with conventional balcony slabs. The study noted that the Schöck solution can also help meet Building Code requirements, without requiring investment in other costly improvements related to the building envelope.