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SAP for Extensions and Renovations

Energy efficiency isn’t just a concern for new dwellings. There are regulations in place that cover home extensions, dwelling renovations and change of use developments and you may need to meet Government targets on CO2 levels.

Why do I need a SAP for an extension or renovation?

If you are renovating or extending an existing residential dwelling, you need to make sure your specification meets the requirements of building regulations (Approved Document Part L1B for England and Wales, and Technical Handbook Section 6 in Scotland).


An extension designed with a high level of glazing may result in a dwelling with increased heating bills in winter. Compliance will be met providing all new construction meets these requirements and a SAP shows the building’s predicted energy use is less than a notional calculation.


If you are building a conservatory that is not thermally separated from the rest of the dwelling, it will be treated as an extension. As such, the above guidance should be followed.

Change of use:

Change of use may be defined as creating new dwellings in an existing building, such as a barn conversion or empty office block. In this case, you will need to make sure all limiting U-Values are met and that new heating systems meet minimum efficiencies.

A SAP calculation is recommended in these cases to ensure all requirements are met and to produce the EPC, which will be required upon completion before any dwellings are sold or rented.

Top Tips for SAP

  • A heavily glazed extension could increase the heating bills in the winter. You may need to combat this by making improvements to the rest of the building.

  • If you are building in an area which requires 'Consequential Improvements' you may need to reserve cash to upgrade existing walls and roofs.

  • You can't knock down a wall and rebuild it as it was. It will need to be insulated in line with current regulations.

  • Our approved SAP assessors can help you find efficient routes to compliance. Contact our team for further information.

  • You will need to make sure all newly-built parts meet current regulations. Depending on the size of your project and where you are in the UK, you may also need to upgrade the existing building fabric and switch to more energy efficient heating, hot water and lighting systems.

  • From April 2018, any existing home with an EPC rating of F or G will need to be renovated before it can be rented out.

The Energist Approach

  • Our accredited SAP assessors share their knowledge with you, interpreting your design drawings and specification to provide cost-effective solutions to pass or to scale back.

  • Our team understand your deadlines and always respond same day. We’re right by your side and offer a 48 hour fast track service and Same Day EPC Guarantee so you won't be kept waiting.

  • We work as an extension to your design team to review your plans before liaising directly with your BCO (if you want us to).

You may also need:

Same-day EPC | BREEAM Domestic Refurbishment | Water Efficiency

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