SAP Calculations for New Builds: What You Need to Know

Building a new home or carrying out a conversion? You will need SAP calculations to demonstrate compliance with Part L of the Building Regulations. Here is what is involved.

What Are SAP Calculations?

SAP stands for Standard Assessment Procedure. It is the government's methodology for assessing the energy performance of new dwellings. Unlike an EPC for an existing property (which uses the simplified RdSAP method), SAP calculations for new builds use the full SAP methodology and are based on the building's design specifications and plans.

When Are They Required?

SAP calculations are required for all new-build dwellings, conversions to create new dwellings (such as barn conversions or office-to-residential conversions), and extensions that include significant glazing (over-glazed extensions). Building control will require SAP calculations to demonstrate compliance with Part L (Conservation of Fuel and Power) of the Building Regulations.

Design Stage vs As-Built

SAP calculations are typically carried out twice. The Design Stage SAP (also called the Predicted Energy Assessment) is produced from the architectural plans before construction begins. It demonstrates that the proposed building will meet Part L requirements. The As-Built SAP is produced after construction is complete, reflecting any changes made during the build. The As-Built SAP generates the property's EPC, which is lodged on the national register.

What Information Is Needed?

To produce SAP calculations, the assessor needs detailed architectural drawings and specifications including floor plans with dimensions, wall, floor and roof U-values, window specifications, heating system details, ventilation strategy, and details of any renewable energy installations.

Cost and Timing

SAP calculations are more complex and therefore more expensive than a standard EPC. Costs vary depending on the complexity of the dwelling but typically range from £150 to £400. It is important to commission the Design Stage SAP early in the project to avoid costly redesigns if the initial design does not meet Part L requirements.