The use of insulating elements to block thermal bridges is a relatively new innovation in the United Kingdom. B&E speaks with Schöck about how architects are reconsidering how they insulate balconies.
Balconies and other cantilever construction elements that extend through the building envelope and breach the insulation layer are notorious for forming thermal bridges. Heat escapes at a much faster rate than in adjacent areas, resulting in significant heat and energy loss.
When the temperature outside drops, the connection point of the cantilever element inside the building also drops dramatically, causing mould and condensation to form. Because the mould formation temperature is approximately 3°C higher than the condensation temperature, it appears first.
Mould growth is well-known as a health hazard, and it is one of the leading causes of respiratory allergies such as asthma. Condensation on the walls will also cause serious deterioration of the plaster and paintwork.
Thermal bridges are classified into two types: geometric thermal bridges, in which a portion of the structure projects through the building envelope, and material thermal bridges, in which materials with different conductivities are combined. Heat is lost due to the ‘cooling fin’ effect of the balcony slab and the thermal bridge created by materials with good thermal conductivity protruding through the insulated façade in the case of non-insulated balcony slab connections. One of the most critical thermal bridges in the building envelope is the non-insulated balcony connection.
Thermal bridging modules have been used in mainland Europe for a long time, but Schöck provided the first in the UK for the Eden Project in 1999. Since then, the construction industry has considered them as a means of complying with changes to the Building Regulations.
Thermal break modules are high-performance, innovative thermal break modules designed to assist architects, designers, structural engineers, and contractors in meeting Part L requirements. Thermal break modules significantly reduce thermal energy loss in connective areas by ensuring homogeneity between cantilever structures and the internal floor due to their thermal insulation properties.
They also transfer load and maintain full structural integrity while keeping inner surface area temperatures well above those that are likely to cause mould formation and condensation.
The modules function by obstructing the flow of heat with a good insulator, such as plastic. Schöck has created a thermal break that is made up of a polystyrene core that is supported by load-bearing stainless steel rods.
Stainless steel bars run through this polystyrene core. The tension and shear forces between the building frame and the balcony are taken up by the bars. A compression module made of a concrete-like material reinforced with microfibres is also included in the bridge.
Thermal break modules differ from traditional methods in that they can be as simple as securing expanded polystyrene insulation to the underside of the soffit. Insulation was installed on the balcony’s soffit as well as 1.5m along the inside room’s ceiling.
A cold area, on the other hand, can spread from the outside of the building, along the ceiling, and all the way to the edge of the insulation. The structure may have been completed and occupied for several years before the problem arises.
The Oxford Institute for Sustainable Development at Oxford Brookes University recently conducted a series of tests on the thermal performance of steel beam junctions using various connection methods, and one of the methods was used in this study.
The goal of the study was to determine the heat loss, minimum surface temperature, temperature factor, and equivalent conductivity that resulted from connecting a steel I-beam with thermal break units, and to compare those values with alternative connection methods and with a continuous beam.
The results showed that the two thermal break units had thermal performances of 0.82 and 0.81, respectively, which exceeded the BRE IP1/06 values and met the requirements of Building Regulations Approved Documents L1 and L2.
Balconies appear to be playing a larger role in meeting our needs for space, both at home and at work, as buildings become taller. Part L revisions make it difficult for the construction industry to adopt these new designs while meeting energy efficiency targets.
However, adversity breeds innovation, and manufacturers and suppliers are demonstrating their ability to think outside the box in order to help reduce the UK’s CO2 emissions through novel methods of preventing heat loss.