Recognised Construction Details ™

Recognised Construction Details ™ (RCD) provides energy assessors, builders, architects and other designers with a suite of independently assessed thermal junction details that have been certified for use in demonstrating compliance with Part L of the Building Regulations.

Easy-to-use tool for assessing
thermal junction details


The 2021 update to Part L and the move towards the governments Future Homes Standard has increased the focus on heat loss through thermal bridges in new homes.

Work by the Future Homes Hub goes further and has reported that it is no longer possible to comply with Part L without the use of calculated Ψ values.

Part L defines two methods to assess thermal bridges; individually modelled values or using a database of independently assessed details such as Recognised Construction Details ™ (RCD).

Get started with Ψ value calculations

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All junctions considered in these Recognised Construction Details have been modelled in accordance with BRE Report BR 497 - Conventions for calculating linear thermal transmittance and temperature factors (2nd edition, 2016) with minimum temperature factors considered in accordance with BRE Information Paper 1/06 - Assessing the Effects of Thermal Bridging at Junctions and around Openings in the External Elements of Buildings (2006).

In addition, the ψ-values given were produced using Physibel TRISCO software which complies fully with the standard BS EN ISO 10211: 2017 - Thermal bridges in building construction. Heat flows and surface temperatures. Detailed calculations.

In addition to providing an assessment of Ψ values Recognised Construction Details also provides a guide to constructing homes that meet the requirements of Approved Document B1: Fire Safety.

  View Guide

About us

The portal has been developed by Building Alliance CIC, using the independently modelled junction details commissioned by the Concrete Block Association and The Aircrete Products Association.

The model Psi Values and the Fire Detailing Guide were authored by Studio Partington Architects.
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