Part A: Understanding Balcony Thermal Bridging
A.1 Overview As a basic principle, heat travels through the path of least resistance. In the context of balconies, these paths typically occur where highly conductive materials penetrate through the thermal barrier to provide structural support for a balcony. Mid and high-rise concrete buildings typically have balconies that are constructed as extensions of the building’s cast-in-place concrete floor slab. The effective R-value for such penetrations is approximately R-1 (0.2 RSI) where insulated opaque wall assemblies typically have effective R-values of R-5 to R-20 (0.9-3.5 RSI). The result is a path of least resistance for heat to escape through to the balcony slab.
“After accounting for windows and doors, exposed concrete slab edges and balconies can account for the second greatest source of thermal bridging in a multi-storey building.” 3
← Illustration of heat loss path through cantilevered balcony slab. The majority of heat loss is through the balcony slab and fenestration.
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