SAP Calculations for new builds, conversions and extensions

Whether your project is for a single dwelling or a site of 200 plus dwellings, a conversion or an extension Eden SAP services can help. With over 15 years’ experience in undertaking SAP calculations we have the expertise to help you achieve compliance, supporting you throughout the process and making compliance practical for you. We will work with you on your new build, conversion or extension project from design stage all the way through to completion.

We don’t offer an ‘off-the-shelf’ SAP service feeding plans into SAP software and getting a pass or fail; or adding on loads of renewables to get a pass. Instead, Eden SAP Services offer an elevated level of service. Working with you taking on board your preferred construction methods to ensure compliance and cost-efficiency.

Engaging us early in the design stage can often save money on your build cost. We can also help you at tender stage. Producing a design specification with you from your planning drawings that will meet Building Regulations. This will give you more certainty in your build costs.

All of Eden SAP services SAP Calculations will include:


  • Working with you/your contractor to achieve compliance taking on board your preferred construction methods and/or renewable technologies to ensuring cost and time efficiency for your project
  • Free U-values for wall, floor and roof elements
  • PEA Predicted Energy Assessment Certificate
  • EPCs produced within 48 hours (2 working days)
  • On-hand advice available via telephone
  • Advice on specification and changes in specification throughout the design and build process
  • Consultation with Local Building Control on your behalf, regarding the SAP Calculations

SAP Calculations for new build dwellings

All new build dwellings are required to undergo SAP (Standard Assessment Procedure) Calculations to measure the energy efficiency of the dwelling in order to conform to Building Regulations Part L1a.

There is no set standard stipulated that a dwelling needs to meet. Instead, SAP assessment calculations are based on a number of factors. For example: dwelling size, design, layout, specification and orientation. This means each dwelling has a unique target to achieve in order to gain compliance.

On some sites there may be several dwellings that appear exactly the same. However, minor differences and orientation can make a difference as each dwelling has a unique target it must meet based on all factors in order to comply. In these cases, Eden SAP Services will agree a fee for each house type and then a lesser fee for each additional dwelling of that same house type.

Find out more about The SAP Assessment Process and How we can help

SAP Calculations for conversions

Properties being converted to residential dwelling(s) require SAP Calculations to show compliance with Building Regulations Part L1b. The same applies to existing residential dwellings being split into multiple dwellings.

Find out more about The SAP Assessment Process and How we can help

SAP Calculations for extensions

Are SAP Calculations required for all extensions? – The short answer is no. However, this will depend on the amount of glazing within your proposed project.

If your extension contains large amounts of glazing, (whether from external openings such as doors, windows, rooflights or glazing that forms part of the walls or roof) you may need a SAP Calculation to be undertaken. The purpose is to show compliance with building regulations Part L1B.

Part L1B of the Building Regulations states that where 25% of the total area (internal floor area) of openings or glazed elements is exceeded, building control will either reject the plans or request further justification for the over-glazing.

For example, if an extension has a floor area of 20m² and has an existing patio door with an area of 4m² (patio door area being covered by extension) then the extension is allowed to have 5m² (25% rule) plus 4m² (existing openings rule) then the total allowable area would be 9m².

The SAP Calculation demonstrates that the carbon dioxide (CO²) emission rate from the proposed extension would be no greater than the dwelling and a notional fully compliant extension of the same size and shape. The method allows you to possibly keep the design with no changes by upgrading existing elements and services within the original part of the house instead. For example, by installing a more efficient heating and hot water system; or increasing the insulation within the existing roof space.

These SAP calculations may well be called other names such as ‘Excess Glazing Calculations’ or ‘Heat Loss Calculations’. All these terms mean the same thing which is where Eden SAP Services can help.

Find out more about How we can help

Help with SAPs at tender stage

Eden SAP Services can help you at tender stage. We will work with you to produce an outline design specification from your planning drawings that will meet the required Building Regulations. This can give you more certainty in your build costs and decrease the chance of unexpected costs if your tender is successful.

To discuss your SAP requirements, please call 03333 448949 or email you can also find out more about how we can help and project examples.