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We are often asked what the difference is between an EPC for a new building, and one for an existing building.

A SAP EPC refers to an Energy Performance Certificate issued by an ‘On Construction Domestic Energy Assessor’, using SAP methodology and software.

What is a SAP EPC?What is a SAP EPC?

Any new dwelling, or dwellings created by conversion or change of use are required to have SAP Calculations carried out. This is the method we use to measure energy performance in newly created homes in the UK. The assessor will then in turn produce an EPC outlining the energy efficiency of that build.

The assessor will use architects plans and drawings, together with detailed information around construction, heating and ventilation amongst others.

EPC’s  for Existing Dwellings

Most EPC’s are required for existing dwellings as they are either being sold or let. This EPC would have previously gone into the Home Information Pack for prospective buyers or tenants to view, however HIP’s have since been discarded. The process followed to deliver the EPC in this case is quite different.

What is a SAP EPC?

A Domestic Energy Assessor will visit the property in person and survey the property. They will then use a more simplified energy assessment called RDSAP (Reduced Data SAP) to create the EPC. If it is difficult to ascertain from inspection how a home was put together, RDSAP can use some age related values and assumptions to help the assessor.

So, the two versions of EPC are fundamentally the same thing – providing a picture of the energy efficiency and energy costs of the dwelling. However, one is based on a very detailed construction and services specification together with architects drawings (SAP EPC), and the other is based on a site survey.

Generally an EPC for an existing dwelling will be less expensive to purchase than one derived from SAP Calculations.

Would you like to discuss your project?

Call us for a chat on 0330 055 34 05 or email

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"For the last few years I have relied upon the professionalism and knowledge of the team at Build Energy to provide economic solutions to meet and improve on current Building Regulations.  I look forward to a continued working relationship with them on our future developments."

Stuart Wright
- Driftstone Homes

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