Free library of 1,500 timber frame thermal details launched on STA website

A free online library of more than 1,500 thermal details and psi-values for timber frame construction has been launched on the Structural Timber Association (STA) website, the Trussed Rafter Association (TRA) said.

The Structural Timber Thermal Details Platform covers single family homes and multi-occupancy apartments. According to the TRA, it includes five generic timber frame wall systems, non-habitable and attic trussed rafter systems, I-joists and metal web engineered timber floors.

The TRA described the platform as a collaboration between Timber Development UK (TDUK), Swedish Wood and Knauf Insulation, with input from Studio Partington Architects and Briary Energy.

Paul Newman, technical director of the STA, said: "This platform provides a significant library of independently calculated thermal bridge details, together with the information needed to support compliance and design optimisation."

What the platform holds

The TRA said the platform is the UK's first online free-to-use generic structural timber thermal details website. Although it concentrates on timber frame at launch, the TRA said it is intended to accommodate other timber construction methods in future, including structural insulated panels (SIPs), mass timber and proprietary systems.

The association, which describes itself as the voice of the trussed rafter and metal web joist industry in the UK and Ireland, said the details for attic truss systems and metal web floors would be of particular interest to its members. Those members include the principal manufacturers of trussed rafters and metal web joists, along with suppliers and professionals.

David Hopkins, CEO of TDUK, said: "There is an overwhelming need to improve the thermal performance of UK housing stock, to lower energy bills and reduce emissions. TDUK is proud to be supporting this project."

Background

The launch follows an earlier signal from the trade bodies. Building performance guidance published online by TDUK and the STA said the STA was developing a web-based thermal details platform due for publication in 2026 to support the introduction of the Future Homes Standard.

The same guidance sets out why the details matter for compliance. It says external wall junction thermal bridging calculations require psi-value calculations, which measure heat loss at an external wall junction and need specialist thermal modelling. It also says all U-values must be calculated in accordance with BRE 443.

Newman said that by making the resources freely available, the STA hoped to help the industry reduce design risk, improve building performance and encourage greater confidence in structural timber systems.

Hopkins said the set of details would give housebuilders and designers the information they need, and that TDUK hoped more housebuilders would choose timber systems as a result.

The platform is hosted on the STA website and holds more than 1,500 thermal details at launch.