A closer look at thermal bridging…
To understand more about how, why and where thermal bridging occurs, we firstly need to look into different building connections outlined in the very initial stages of a construction project. The bridging occurs when heat passes through a material that is more conductive than the materials around it, causing a transfer of energy, so any connections where this is a possibility need to be carefully considered.
Thermal bridges reduce efficiency by bypassing any insulation which acts as a ‘bridge’ for energy, creating spaces that cannot hold temperatures. Thermal breaks are durable, effective and, most importantly, cost effective solution to thermal bridging.
Applications where thermal bridging is most likely to occur includes masonry shelf angles, column bases, foundation walls, balcony / canopy installations, roof penetrations and cladding attachments. These are key areas where energy-saving thermal breaks are essential to the efficiency of the building.
Thermal break materials can be used anywhere that a transition exists within the building envelope. The revolutionary solutions work by isolating the temperatures using an inert, closed-cell polymer, which has an ultra-high density. This ensures that the thermal break solution is not only insulating and water resistant but strong, which, when working with steel, is often a requirement due to the high-load capacity of the overall structure
The advantage of using steel as a building material in construction projects has long been recognised by designers and specifiers, making it a revolutionary material within the building sector. The most traditionally used material for commercial constructions, it is favoured due to its ability to bind well to concrete, it is strong and relatively cost effective, and so, specified for a large range of building projects. With an approximate 90% market share for single-storey industrial buildings, its strength and versatility are big selling points, although thermal conductivity and performance isn’t always considered.
Column base applications
Within column base applications, the internal steel columns usually extend through the building envelope’s floor slabs and insulation materials. When creating low temperature buildings that are required to hold cooler temperatures, such as freezer rooms or cold storage facilities, the steel can act as a bridge.
For a project like this, Armathem would provide a thermal bridging solution to be installed directly under the steel column bases that bridge floor slab insulation. Support columns can then be passed through the non-load bearing slab insulation to the warm ground beneath, effectively short circuiting the insulation barrier.
Masonry shelf angles
Working with masonry veneer walls means tie-backs and shelf angles have to be specified to assist with load bearing. They help transfer the masonry load back to the building’s structural frame – usually the steel or concrete slab edge, interrupting the continuous insulation of the wall assembly. These can create significant thermal bridges, meaning meeting energy code regulations can be more difficult.
The Armatherm™ FRR structural thermal break material can be used behind the shelf angle as a thermal break within the insulative layer. The Armatherm™ thermal break signiﬁcantly reduces heat loss via the shelf angle connection.
Balconies and canopies
Balconies and canopies use cantilevered or steel elements, usually connected to slab edges or spandrel beams on the interior side of the thermal envelope, passing through the insulation and air barrier levels. Our thermal breaks are capable of transferring load in moment and shear connections, without creating significant rotation. It’s imperative that a structural thermal break maintains the structural integrity of the balcony or canopy connections while minimising the heat flow.
The most common cause of compromised continuous insulation is structural components, like clips and girts, which can create thermal bridges when connected to steel stud framing. The insulation efficiencies of the wall assemblies improve considerably when an effective thermal break solution is incorporated, with the highest levels rising to 98% efficiency. These support connections prevent heat loss and subsequent condensation issues associated with thermal bridging.
The roof of a building is where penetrations such as davits, anchors and supports for dunnage can be found extending through the thermal envelope and roof insulation, resulting in non-continuous insulation. These are usually connected to interior trusses or structural elements creating a thermal bridge and heat flow.
Implementing a sophisticated thermal break at these connections can increase efficiency by up to 60%, while also helping to avoid condensation issues, which occur when colder temperatures are transferred inside. Neglecting cold transfers can encourage condensation that can lead to the formation of mould, which can often be seen on ceilings where roofing systems have been installed, or the interior walls of buildings that feature a cladded façade or balcony which have not been isolated correctly. Along with being unsightly, mould can also cause health issues if it goes untreated, making it a detrimental issue which can affect the aesthetic of a room’s interior.
Thermal bridging within foundation walls creates heat loss at the foundation perimeter. This reduces the exterior wall’s effective R Value. Foundations are part of a buildings’ thermal envelope. The intersection at a slab on grade to foundation wall and exterior wall to foundation transition are both areas where heat flows out of a building. This is due primarily to non-continuous insulation details.
Heat losses at the base of the foundation wall can be reduced by as much as 60% by using an efficient, structural thermal break. Armatherm™ 500 is a load bearing, thermal break material manufactured in several densities to provide a range of load capacities with R values as high as R 4.6 per 25mm.
Thermal bridging at a foundation wall transition can be reduced further by increasing the length of the slab insulation.
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