Best Practice Solutions and Details
The most effective way to minimize the heat transmittance of structural components (balconies, parapets, canopies) penetrating the insulation layer is to thermally separate the exterior structure from the interior structure. With the aim of decreasing thermal losses at the connection, Schöck Isokorb® structural thermal breaks optimize the function and performance of each integral element at the junction. A primary goal for designing and selecting proper thermal bridging strategies is to comply with UK Building Regulations Part L where minimum requirements for the temperature are provided.
The general concept is that more conductive materials such as reinforced concrete (λ = 2.2 W/(mK)) or structural steel (λ = 50 W/ (mK)) at the connection are replaced with expanded polystyrene (EPS, λ = 0.031 W/(mK)) with a minimum thickness of 80mm to give an effective thermal separation. This is non-structural and constitutes the main body and surface area of the thermal break. To conserve the structural integrity between the exterior elements (e.g. balconies, canopies) and the interior structure (e.g. floor slab), reinforcement bars are used to connect both sides and transfer loads (tension and shear). These traverse the insulation body of the thermal break and are made of high strength stainless steel (λ = 15 W/(mK)), instead of carbon steel (λ = 50 W/(mK)). This not only reduces thermal conductivity, but also guarantees longevity through its inherent corrosion resistance. To transfer the compression loads, the thermal break uses special compression modules made of high strength concrete (λ = 0.8 W/(mK)), as these offer better thermal performance in when compared with compression bars made of carbon steel or even stainless steel.
A thermal modelling study was undertaken by Oxford Brookes University to determine the effectiveness of Schöck Isokorb®. The following sections show the results for different applications with different solutions.