CLG put thermal bridging confidence factors on hold

CLG have published a departmental circular regarding Building Regulations 2010, giving further guidance on Parts F, J and L and the energy efficiency requirements. It is aimed at building control bodies but is very relevant to OCDEAs.

It contains one crucial announcement that is of particular relevance. ‘Confidence factors’ for psi values have been put on hold until thermal bridging accredited construction details schemes are in place:

“C14 At the time of publication of this circular letter no accredited construction details schemes have been approved by the Secretary of State. Until such time that accredited construction details schemes have been approved, the calculated value of linear transmittance may be used in SAP without any performance penalty being added where this has been calculated by a suitably experienced and qualified person and the builder has provided information about the way the detail is to be constructed to the Building Control Body.

"C15 Upon approval of accredited construction details schemes a further circular letter will be issued to reinstate the margins to be applied to the calculation of thermal transmittance as set out at paragraph 5.12(b) to Approved Document L1A and paragraph 5.7(b) to Approved Document L2A.”

NES Technical Manager Dyfrig Hughes commented:

“Housebuilders will be delighted at this news as it will make it easier to meet TER targets in the short term. However, the danger is that it will slow down the process of setting up thermal bridging accredited construction details schemes as the incentive of removing confidence factors will no longer be there.”