The British Board of Agrément and Robust Details Limited have joined forces to form a joint venture called Constructive Details Limited. This new company will provide an accredited thermal bridging scheme to meet the requirements of Approved Document L1A (dwellings, section 5.12) and L2A (non-dwellings, section 5.7).

Constructive Details Limited is intended to provide the construction industry with an appropriate solution, following the requirements of part L 2010. Through the scheme, users can avoid the 25% penalty in ψ-value(s) and the even more unfavourable scenario of using a default y-value of 0.15 when unaccredited details are used.

The two partners will contribute to the joint venture as follows:

BBA
Building Physics capabilities in modelling and testing
Technical competency scheme experience (See U value scheme)
Site inspection/assessment expertise (see Inspection schemes)

RDL
Experience from Part E Robust Details
Existing administration infrastructure

The BBA and RDL can also offer a common network of existing stakeholders in the construction industry, from manufacturers (Agrément Certificate) to builders (Acoustics scheme by Robust Details). During the development process of Constructive Details, we have been engaging with construction industry representatives to ensure the scheme reflects the needs of manufacturers, builders and specifiers.

The main features of the Constructive Details scheme are:

• inclusion of an Approved Thermal Modeller scheme to assess the competency in producing correct ψ-value(s)
• risk based assessment of robustness including site validation to access the buildability of a junction
• full web-based accessibility will be provided once the Constructive Details are published on the website. Builders will be able to register plots using these details and obtain a certificate of registration for submitting to Building Control as evidence of compliance
• regular monitoring of site performance – applies to the dwelling market only

The benefits of the scheme include:

• the use of reliable, transparent and likely beneficial ψ-value(s) of junctions to be used in SAP and SBEM calculations
• any other ψ values will incur a 25 % penalty which will have to be compensated by other means, eg thicker insulation, less habitable space and less favourable carbon emissions calculations
• for the dwellings market, participation in the scheme could attract potentially lower charges from the Building Control Body
• It fulfils the Part L requirements for both the dwelling and non-dwelling market, provides a transparent route in the approval of products, systems and components and builds on knowledge transfer that has been so successful in the Part E model.

Constructive Details Limited is working closely with the Department of Communities and Local Government (DCLG) on formulating a document to provide the basis for the accredited details scheme. A scheme operating document has already been presented to the government by the certification bodies and due consideration will be given in the December 2011 consultation meetings.