Building Regulations - SAP - SAP and Part L compliance

SAP is the tool used for calculating the Target Emissions Rate (TER) and Dwelling Emissions Rate (DER) carbon dioxide emissions necessary for demonstrating compliance with Part L.

A key change from the 2002 Part L regulations is that compliance is now based upon whole building carbon emissions, with the former compliance methodologies (elemental, target u-value and carbon index) now scrapped.

This important change means that building designers must now take a more holistic approach to the design of their buildings, as there are many factors which contribute towards the buildings carbon emissions level and energy efficiency performance, including:

  • constructional element performance, i.e. u-values of walls, windows, floors, roofs, etc, and thermal bridging
  • building air permeability level
  • heating system specification and fuel type
  • hot water system specification and fuel type
  • ventilation system specification
  • lighting system specification
  • building shape and orientation

In order to achieve compliance with Part L, designers must show that the predicted annual carbon emissions from the building (known as the DER) are less than or equal to a calculated target level (known as the TER). Designers have complete flexibility to 'trade off' the performance of each of these aspects against each other to ensure the emissions fall within the annual target.

Improvements to the building fabric elements or building services types / efficiencies improve the DER, allowing compliance to be achieved.