SAP Assessments 

Part L Building Regulations are a key component of UK building law that focus on energy efficiency and the conservation of fuel and power in buildings. They set strict standards for new and existing residential and commercial properties, ensuring that homes, offices, and public buildings reduce carbon emissions and minimize energy consumption. Part L covers aspects such as insulation, heating and cooling systems, lighting, ventilation, and renewable energy integration, making buildings more sustainable and cost-effective to run. Compliance with Part L is essential for new builds, renovations, and extensions, helping property owners meet legal requirements while contributing to the UK’s carbon reduction targets. Updated regularly, the regulations now encourage low-carbon technologies and improved building fabric performance, supporting the transition to greener, energy-efficient buildings.

SAP stands for ‘Standard Assessment Procedure’. It is the only official, government approved system for assessing the energy rating of a new or converted home. SAP assessors must be accredited and registered with a certification body; we are members of Elmhurst Energy. In July 2022, the regulations were updated so any new projects are assessed using the software SAP10.2.

SAP Calculations are a requirement of Part L of the Building Regulations, and are needed for all newly built and converted dwellings. The SAP Calculations establish an energy cost based on the construction of the home, its heating system, internal lighting and any renewable technologies installed. The Calculation also provides evidence that the building complies with building regulations set out in Part L.

In order to meet current Building Regulations, house builders need to establish a ‘pass’ on their SAP Calculations. Without it, Building Control will not sign off the development and the property cannot be let or have a mortgage raised on it for purchase.

But there are other reasons to care about SAP. A good SAP assessor can work with the builder and architect to minimise its energy use and carbon emissions.  A great SAP Assessor can do all of this AND save money on the build cost!

All new build properties in the UK require a SAP Calculation. In England, each proposed home is compared against a notional dwelling, a benchmark model defined by Part L building regulations, to ensure compliance. Key metrics include the Dwelling Fabric Energy Efficiency (DFEE), which measures how well the building fabric retains heat; the Dwelling Emission Rate (DER), which must not exceed the Target Emission Rate (TER); and the Dwelling Primary Energy Rate (DPER), which tracks overall energy use from all services.

New build houses are also required to meet limiting U-values, which set the minimum energy efficiency standards for key building fabric elements such as walls, roofs, floors, and windows. These U-values ensure that heat loss through the building envelope is minimized, improving overall thermal performance and reducing energy consumption. Compliance with these standards is a crucial part of SAP assessments and helps achieve a higher Energy Performance Certificate (EPC) rating. By meeting or exceeding the limiting U-values, developers can deliver energy-efficient homes that are not only Part L compliant but also cost-effective to heat and environmentally sustainable.

SAP calculations for conversions evaluate the energy performance of existing homes undergoing renovations, extensions, or changes of use. While limiting U-values still apply to ensure that walls, roofs, floors, and windows meet minimum insulation standards, conversions do not have the same energy targets as new builds. Instead, the SAP assessment produces an Energy Performance Certificate (EPC), which reflects the overall efficiency of the property, taking into account building fabric, heating systems, ventilation, and renewable energy options. Accurate SAP calculations for conversions help homeowners and developers achieve legal compliance, improved EPC ratings, and more energy-efficient homes.

A SAP Rating is a way of measuring the heat loss of a dwelling and comparing energy performance of different homes; it results in a figure between 1 and 100+ (100 representing zero energy cost and anything over means you are exporting energy). The higher the SAP rating, the lower the fuel costs and the lower the associated emissions of carbon dioxide. 

Stage 1 - the 'Design' stage

SAPs must be calculated and submitted to the relevant Building Control Officer (BCO) or your Approved Inspector (AI) at the point when you make your Building Control Application.  Predictive Energy Assessments (PEAs) can be issued at this stage in case you want to market the property prior to completion

Stage 2 - the 'As-built' stage

Produced when the build is completed. Compliance documentation that shows a “pass” must be produced for presentation to your BCO or AI. Any changes that were made to the build specification must be incorporated in the "As Built" assessment and the results from your Air Testing regime entered into the calculations. Your final EPC will be based on the information confirmed at this stage.

Your SAP Assessor will work from architects drawings and construction information, together with a full heating and ventilation specification. Drawings need to be scaled, accurate and show all elevations, sections, floor and site plans; Autocad is our preferred software. 

Once complete, a SAP calculation is capable of producing detailed reports, including the all-important Building Regulations Compliance paperwork.

The key point is to start thinking about SAPs early. 

Involving a SAP assessor early in your project is essential to ensure compliance with Part L building regulations and to achieve optimal energy efficiency and EPC ratings. A qualified assessor should be consulted during the design stage of new builds, conversions, or major renovations, allowing them to advise on insulation levels, heating systems, ventilation strategies, and renewable energy integration. Early involvement helps identify potential issues before construction begins, streamlines the SAP calculation process, and ensures that the property meets energy performance targets. Engaging a SAP assessor at the right stage can save time, costs, and future retrofit work, while guaranteeing a compliant, energy-efficient building.