This really is probably the most frequent question asked. Check out Andrea’s video explanation above, or read the full explanation here on the right.

The average price range can be between £100 – £300, this can be depending on the complexity and size of the property. If you also need an Energy Performance Certificate (EPC) at the end of it there could be an extra charge of about £50 to register the EPC on the national register. For multiple properties of similar types, then special discounts might be available.

Before we explain the difference, this is what you will require depending on your project.

For a new build property you’ll need – SAP calculations and an EPC.

For dwelling change of use or conversion you’ll need – Sap Calculations and an EPC.

For overglazing on an existing dwelling you’ll – Sap calculations only.

SAP or Standard Assessment Procedure are the calculations of pre defined data set of a buildings design that’s put together to display the energy performance of a building. An EPC or Energy Performance Certificate is a summary report produced by the Sap calculations which produces a SAP rating from 0 to 100. This rating is expressed on the EPC as A the highest to G the lowest. It will also list recommendations that would enhance the rating of your dwelling.

There are actually two types of EPCs. First is a SAP EPC which is created from building plans when all of the elements of the construction are known. This will normally be needed by building control to demonstrate that a dwelling complies with specified targets required by the building regulations. Building control would must also see the SAP calculations which illustrates in greater detail whether the many elements going into the property comply with the building regulations.

The 2nd type of EPC is the common one that will be needed for anybody who is marketing, or renting a property. This type of EPC uses what’s called rdSAP, which means Reduced Data Standard Assessment Procedure, and is used where particular thermal values of, for example, the walls, roof, floors, etc, usually are not precisely known on an established property. In this instance assumed thermal values are used according to the age of the property. This type of EPC will be no use to demonstrate compliance with any building regulations. Sometimes building control would simply ask you for the EPC, but what they would really need are the Sap calculations (which is the data behind the EPC) and the SAP EPC (which is a summary report of the Sap calculations).

Still perplexed, then phone us for additional advice.

These are the finished set of SAP calculations produced when the dwelling has been completed to hopefully demonstrate that it is compliant with Part L1A of the building regulations. Prior to the construction starting, it should have had some “Design Sap” calculations to demonstrate that the planned construction, on paper at least, will be compliant with Part L1A.

Unfortunately this is not some thing that can be done by yourself. Sap calculations have to be carried out by an On Construction Domestic Energy Assessor or OCDEA, working with approved Government program. The Assessor has to be certified under one of the certification schemes and is also regularly audited to keep up their qualification.

Your Assessor would advise you of exactly what is needed. Typically you would need the following:

• Floor Plans to include sections and elevations
• Orientation of the property
• Construction specification of walls, roof and floors
• Specification for all doors and windows
• Primary and secondary heating
• Provision for providing  hot water
• Any renewable technology (if any)

All new dwelling need to have Sap calculations to demonstrate compliance with Part L1A (Conservation of fuel and power in new dwellings) of the building regulations.

It’s now modern to have large bi-folding doors, sky lights and large quantities of glazing on new extensions. But with the existing building regulations the amount of glazing must be no more than 25% of the floor area of the new extension. So over compensations on the thermal elements in other parts of the property will need to be made to show the CO2 emissions coming from the current house along with the planned extension is not any worse than the existing house and an extension whose glazing is within the permitted amount judged against Part L1B of the building regulations.

You will require SAP calculations to find solutions and illustrate compliance.

For anyone who is altering the use of a dwelling, you will need Sap calculations. {The new dwelling will have to comply with Part L1B of the building regulations.}

You will need Sap calculations for any of the following: 

• Building a new property
• Changing the use of an existing property (e.g, a barn conversion, commercial building to residential)
• Extensions with more than 25% glazing
• Opening up the main house to an existing conservatory
• Extension where the extension is more than 50% of the original property wall area
• Garage conversions
• If requested by building control

This list is not exhaustive. Give us a call, if you are unsure if you require them.