What Is a SAP Assessment in Construction?

SAP stands for Standard Assessment Procedure. The UK government uses it to measure the energy performance of homes. BRE developed the method and published the first version in 1992. Building Regulations have cited it since 1994. The assessment gives your home a score for energy efficiency and carbon emissions. A low-energy home scores better. A better score means lower heating bills for the people who live there.

You need one because the law requires it. Part L of the Building Regulations covers the conservation of fuel and power. It sets energy limits for new homes. A SAP calculation shows your design meets those limits. Since 2008, every new home under construction in the UK needs a Predicted Energy Assessment and an On Construction Energy Performance Certificate. Building Control will not approve your project without the right paperwork. The rules also tightened in June 2022. Part L 2021 requires new homes in England to produce about 31% less carbon than the 2013 standard. Your design has to prove it, and the SAP calculation is the proof.

New Build Homes:

Every new dwelling needs a SAP assessment. This covers houses, flats, and bungalows. It also applies to each plot on a multi-home development.

Conversions and Change of Use:

You need one when you convert a building into a home. Examples include turning a barn, office, shop, or garage into a dwelling.

Extensions and Major Refurbishments:

Some extensions need a SAP calculation. The need depends on the size of the extension and the amount of glazing. Ask your assessor or your Building Control officer before you start work. Not sure which rule applies to your project? Call Nationwide Surveyors free on 0800 048 7474 or send your details through our contact page.

A SAP assessment has two stages. You need both.

Stage 1: Design Stage (SAP Calculation and Predicted Energy Assessment)

You complete this stage before building starts. The assessor reviews your plans and specification. They calculate the expected energy performance. The report goes to Building Control as part of your approval. You send the assessor your floor plans, elevations, and section drawings. If you do not have drawings, our floor plan service helps.

Stage 2: As-Built Stage (On Construction EPC)

You complete this stage when building finishes. The assessor checks what the builders installed. They update the calculation with the real insulation, windows, heating system, and airtightness results. Then they issue the On Construction Energy Performance Certificate. You need this certificate before you sell or rent the home. Buyers, tenants, and solicitors ask for it.

The assessor looks at every part of the building that affects energy use. The main items are:

• Wall, roof, and floor insulation
• Window and door types
• Airtightness of the building
• Heating system and controls
• Hot water system
• Ventilation
• Lighting
• Renewable energy such as solar panels or heat pumps

Small design choices change the score. A better boiler, thicker roof insulation, or one extra solar panel often moves a failing result to a pass.

People often mix up the two. Here is the difference.

A SAP assessment is the calculation. It checks a new design against Building Regulations. An EPC is the certificate. It shows the energy rating of the finished property on a scale from A to G.

For a new build, the SAP calculation produces the On Construction EPC. For an existing home, you need a standard EPC instead. Landlords of existing properties cannot let a home rated below E unless they hold a valid exemption. Read more on our domestic EPC page or our commercial EPC page.

1. Request a quote. Tell us your property type and postcode. Our online form gives you a price in 30 seconds.
2. Send your documents. Share your plans and your planned materials and heating system.
3. Receive the design stage report. The assessor runs the calculation and tells you if the design passes.
4. Adjust the design if needed. The assessor suggests the most cost-effective fixes.
5. Submit the report to Building Control. They approve your plans.
6. Build the home. Keep records and photos of insulation and key installations.
7. Complete the as-built assessment. The assessor checks the finished work.
8. Receive your certificate. You get the On Construction EPC by email.

Follow these steps to avoid delays and extra costs.

• Book your assessor before you finalise the design. Early advice costs less than changes on site.
• Send complete drawings and product details. Missing information causes most delays.
• Keep your specification the same as your calculation. A different boiler or window changes the result.
• Photograph insulation before you cover it. The assessor needs proof of what sits behind the plasterboard.
• Tell your assessor about any change during the build. Do this the same week.

A SAP assessment is rarely the only requirement. Builders and developers often order these services together:

• Fire Risk Assessment for commercial or multi-occupancy buildings
• EICR for electrical safety checks on existing wiring
• Building Surveys for older properties you plan to convert
• Gas Safety Certificate for homes with gas appliances
• Legionella Risk Assessment for shared water systems

What is a SAP assessment in simple words?

It is an energy check for new homes. An assessor reviews your design and your finished build. They confirm the home meets the energy rules in Building Regulations.

Who needs a SAP assessment?

Anyone who builds a new home or converts a building into a home needs one. Some extensions need one too.

How long does a SAP assessment take?

The time depends on the quality of your drawings and how quickly you send details. Complete information speeds up the process. Ask us for a timeline when you request your quote.

Does a SAP assessment reduce energy bills?

The assessment itself does not cut bills. The results show which design choices lower running costs. You choose those options before you build.

What happens if my design fails?

The assessor tells you which items to change. Common fixes include better insulation, upgraded windows, a more efficient heating system, or solar panels. You adjust the design and the assessor runs the calculation again.

Is SAP the same across the UK?

Each nation sets its own building rules. England and Wales use Part L. Scotland and Northern Ireland follow separate standards. Ask your assessor which rules apply to your site.

What is the difference between SAP and the Green Deal?

SAP is a calculation method for dwellings. The Green Deal was a government scheme to fund energy improvements for existing homes. They serve different purposes.