Frequently Asked Questions
Approved Document L1 (ADL1) requires the impact of thermal bridging to be limited in new homes. There is guidance on how this should be done with the ADL1.
There is a specific requirement to account for the heat loss through thermal bridging within the SAP calculation software. In the past, it might have been possible to have a compliant SAP assessment by using the default Y value (the Y value is the total of all Ψ values). However, in the 2021 update of the Building Regulations, the default Y value was increased to 0.2W/m2k. As a result of this change, in most case, it is no longer possible to use the default Y value and have a compliant SAP calculation.
The impact of these changes to the regulations has meant that some level of thermal bridging calculation will be required on almost all new homes. ADL1 describes two allowable approaches to using calculated Ψ values:
a. Use construction joint details calculated by a suitably competent person following the guidance in the Building Research Establishment’s BR 497 and the temperature factors set out in the Building Research Establishment’s Information Paper 1/06.
b. Use junction details from a reputable non-government database containing independently assessed thermal junction details, such as Local Authority Building Control’s Construction Details library.
Recognised Construction Details allows you to use option b.
Unfortunately, not. The details must be used and built as shown
It is important that the detailing and specification notes shown on the drawings are followed. You will be expected to provide information on Ψ values at the design stage and also evidence that the new home has been built in accordance with the design details.
Approved Document L1 includes detail on the information you will be required to submitted to the Building Control Body to demonstrate as-built compliance and includes photographic records.
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 BS EN ISO 10211: 2017 - Thermal bridges in building construction. Heat flows and surface temperatures. Detailed calculations.
No.
All the information on the Recognised Construction Details website is free to use, to anyone, without the need for registration.
To enhance the user experience, we have introduced the option to become a registered user of RCDs. There is no cost attached to registering, but there are some user benefits. Once registered you will have your own user area where you can create projects and store specific details with that project. It will then be possible to download all the details associated with a project.
There are currently no details included for timber ground floors or timber party floors.
These may be added in the future.
No, although there are benefits, see the answer to
Do I need to pay to download details or register?
If a specific detail is updated, drawings will be replaced. However, a copy of the original drawing will be retained on the site in the archive.
Changes, revisions and updates will be recorded in the Guidance/Updates section of the website. A complete revision history of each document will be recorded and access to superseded drawings will be maintained.
