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SAP Calculations for Extensions

Building an Extension on your house? 

Did you know that If your proposal contains large areas of glazing you will likely need SAP calculations services to ensure your proposal meets energy efficiency requirements.

Whatever the size of your project, Elmhurst Energy Services can complete SAP calculations to ensure your designs comply with the Building Regulations.

Call us now on

01455 883 259

 and discuss your project with us, there’s no obligation and we’re happy to advise you.

Or why not complete the form linked below.


When are SAP Calculations for Extension required?

Part L1b of the Building Regulations states that the total of area of new glazing should not "exceed the sum of 25% of the total floor area of the extension" unless 'compensating measures' are used elsewhere in the plans. If the sum is greater than 25% than the proposal will need to be justified to Building Control. 

It is likely that extensions will exceed this amount as most individuals prefer to let more light in and maintain the appearance of open space with large glazed doors and windows all round the extension.

Read the regulations here: L1B Conservation of fuel and power in existing dwellings- 2010 edition, with 2010,2011,2013 and 2016 amendments.

What Elmhurst Energy Services can do?

SAP Calculations are used to demonstrate that "reasonable provision" has been made in order to make the property comply with Buillding Regulations, regardless of the amount of glazing included. Our expert consultants have over 20 years of experience in this area and can guide you through all the options for what needs to be done. 

What we do to ensure compliace:

1. We use SAP2012 to calculate the CO2 emissions for your existing dwelling along with your proposed extension.

2. We then calculate the CO2 emissions for the existing dwelling this time including a 'notional extension'. A notional extension is an extension that meets the minimum standards of Approved Document L1B.

3. Compliance is achieved provided the “proposed” CO2 emissions are no greater than the “notional” CO2 emissions.
















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