In order to achieve compliance with the Building Regulations Part L, it is important to recognise that the production of successful SAP Calculations is part of the overall process, and, in reality you should never begin construction unless you know that you are building to a specification that will meet the requirements.
If your SAP fails at design stage there is little to worry about – as this is a desk based exercise which is carried out before construction commences. The assessor will model different variations of the design if the initial specification doesn’t show compliance – and make recommendations as to alternative ways that the design can be made to meet the requirements.
However, if your SAP fails at as-built stage it may cost a considerable amount of money to fix. You may not have installed sufficient insulation or used the wrong type of heating and ventilation systems during construction – and this, in turn, may require extensive remedial action and / or new systems installed in order to achieve a successful SAP rating.