Evidence compliance and generate psi values for SAPs.
Thermal bridging analysis identifies ‘breaks’ in building insulation that can be responsible for additional heat loss.
Analysis is required to deliver comfortable, energy efficient properties.
Recent updates to the Building Regulations require thermal bridging to be measured more comprehensively for both residential and non-residential developments.
Our building performance specialists support developers and constructors to generate bespoke thermal bridging values to demonstrate compliance and deliver efficient properties and projects.
For developers regularly building to the same specification, generating bespoke results can be more cost-effective than changing fabric build ups or adding mitigation measures on multiple sites.
Thermal bridging occurs when a building junction conducts significantly higher heat transfer than its surrounding parts.
Analysis assesses areas where insulation is not consistent or is broken by structural elements – such as wall to roof junctions, wall to floor junctions, and window lintels, jambs or sills – to ensure insulation measures will not be undermined.
Analysis looks at the thermal conductivity (heat loss) through aspects of the building envelope. The thermal bridge is the sum of additional heat loss, from internal to external, caused when two construction elements meet.
Heat loss from a thermal bridge is measured as a psi value, measured in watts per metre (w/m). Lower psi values indicate less heat loss from a junction.
These values contribute to the SAP assessment, and have a direct impact on the Dwelling Emission Rate (DER), Dwelling Primary Energy Rate (DPER), and Dwelling Fabric Energy Efficiency (DFEE).
Adopting a ‘fabric first’ approach supports designers to reduce thermal bridging. This typically requires use of high levels of insulation, paying particular attention to the design of building junctions. Narrower breaks in insulation between structural supports and using materials with lower heat conductivity will help to reduce thermal bridging. Such design consideration also reduces the risk of surface condensation on internal surfaces, lowering the risk of mould growth.
For developments working to achieve the challenging passive house standard (Passivhaus), this approach is crucial.
While it is not possible to achieve a thermal bridge free design altogether, good planning and early consideration of junctions can help to significantly reduce additional heat losses.
Thermal bridging is considered as part of the SAP and SBEM assessments which are a mandatory requirement of building regulations for all residential and non-residential new-build developments.
The same modelling technique can be used to measure the risk of surface condensation for specific junctions. In some instances, building control may require this as evidence of a compliant design, irrespective of the property’s SAP requirements.
The following measurement methods are available to demonstrate compliance:
IN PRACTICE – This method is available to all – though results depend on the quality of your design – and is recommended where the same construction specification is being used repeatedly on multiple developments.
IN PRACTICE – This option can produce high performing psi values without the cost of bespoke calculations. It is only available for the most common construction designs and only when the specific insulation products listed in the psi value are used on site.
IN PRACTICE – This option is only appropriate for renovation or extension projects. It is not recommended for new developments.
NB: Accredited Construction Details (ACDs) are no longer a route to compliance, since the details in this approach no longer reflect modern building practices.