Once the quotation was accepted and all drawings and specifications were received, we instructed our energy team to carry out the SAP calculation, water efficiency calculation and simplified overheating assessment. A couple of weeks later, the energy team got in touch with the client to discuss the SAP calculation which was unfortunately failing. The assessor recommended having some PSI Values calculated on this timber frame dwelling. SAP calculations, under the old regulations, could use accredited construction details (ACD’s) but under the new regulations, these are no longer accepted. Calculating custom PSI values to work out the heat loss at a junction can have a positive effect on the SAP calculation, which in this case it did. The energy team calculated 6 PSI values to begin with on the junctions they believed it would have the best improvement on. Once these were calculated they were input into the SAP calculation, and it was then compliant with Part L (conservation of fuel and power) of the Building Regulations.

The next step of the design process was the overheating assessment. There are 2 options to comply with Part O, a simplified overheating assessment and a TM59 dynamic thermal modelling assessment. A simplified assessment is cheaper and quicker, however if it fails, there is limited design flexibility so recommendations are minimal. On this particular job, our client had opted to go with a simplified overheating assessment. This failed and the only recommendation the assessor could make was to reduce glazing which the client didn’t want to do. We recommended a TM59 which uses specialised software (TM59 CIBSE) to model the building and run heating and cooling simulations to see the effect on the dwelling. It was initially failing on this, but with 1 minor change to the aperture opening which was an easy solution to the client, it passed.

This project wasn’t the most straightforward and several problems arose, but ATSPACE were able to support, guide and most importantly, work with the client to get this project compliant.