Sustainability and energy services

Part L1B (SAP calculations for an extension involving an existing conservatory)

Removal of wall between kitchen and conservatory, Bracknell

This project at a detached, 1995 built house involved undertaking the SAP calculations and supplying the Part L1B consultation for the opening up of the kitchen, through the removal of an external wall into the conservatory and the upgrading of the conservatory roof.

The home owners wanted to increase their kitchen area, but the opening up of the kitchen to the already built conservatory would technically be an extension and would need to comply under Part L1B.  This can be a tricky situation, as no new thermal elements were planned, but those in existence may not comply with current minimum requirements.  In addition, this project then added a large amount of extra glazing, thus falling foul of the 25% + lost opening area stipulation in Part L1B. The final part of the jigsaw was that the home owners wanted to replace the glazed roof area of the conservatory with a standard roof, which is not always the easiest retrofit.

Fortunately, the change to the roof structure reduced (but did not entirely eliminate) the issue with glazing area. The roof structure itself was replaced by a company specialising in this type of work and after several conversations, they were able to supply reliable information for a u-value calculation to be undertaken for the new roof. 

This still meant that improvements elsewhere in the property were required to demonstrate a Part L1B compliant carbon emissions figure for the whole house and in this case, the project also involved the replacement of all the dwelling windows and the installation of a new, more efficient gas boiler, both of which led to a comfortable attainment of compliance.

The required Part L1B paperwork and report were issued to Building Control and the project is a good example of the benefits of engaging a SAP assessor trained in this area of the Building Regulations, an area of strong expertise at Blewburton Limited.

L1B conservatory