This is quite possibly the most common query asked. Have a look at Andrea’s video explanation above, or read the full explanation here on the right.

This can differ considerably dependant upon the size and complexity of the dwelling, however an average cost range would be between £120 – £300. There may be another cost of approximately £50 if an EPC is called for at the end of the construction. Special discounts would typically be available for multiple properties especially when they are of the identical type of structure.

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 show the energy efficiency of a property. EPC is short for Energy Performance Certificate and it’s a summary statement from the SAP calculations in an straightforward report, which could also be used to sell or rent out a property.

There are actually 2 types of EPCs. First is a SAP EPC that is produced from building plans when all of the components of the construction are known. This will normally be needed by building control to show that a dwelling meets specified targets required by the building regulations. Building control would also have to see the SAP calculations which shows in detail whether all of the components going into the property conform to the building regulations.

The second sort of EPC is the standard one that will be needed for anyone who is selling, or renting out a property. This type of EPC uses what’s called rdSAP, which is short for Reduced Data Standard Assessment Procedure, which is used where specific thermal values of, for example, the walls, roof, floors, etc, usually are not precisely known on an existing property. In this instance assumed thermal values are used based on the age of the property. This type of EPC would be no use to show compliance with any building regulations. Sometimes building control would simply ask you to get an EPC, however what they would really require are the Sap calculations (which is the data behind the EPC) and the SAP EPC (which is actually summary report from the Sap calculations).

If you are still confused, after that phone us for further information.

These will be the final set of SAP calculations generated when the building has been completed to confirm that it is compliant with Part L1A of the building regulations. Prior to the project starting, it should have had a set of “Design Sap” calculations to show that the proposed building, in theory at least, would be compliant with Part L1A.

No, this is not some thing that you can do yourself. The calculations have to be carried out by an On Construction Domestic Energy Assessor or OCDEA, working with approved Government software. The Assessor must be certified under one of the certification schemes and is also regularly audited to keep up their certification.

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 show compliance with Part L1A (Conservation of fuel and power in new dwellings) of the building regs.

It’s now quite modern to get large bi-folding doors, sky lights and large quantities of glazing on new extensions. However with the latest building regulations the quantity of glazing must be no more than 25percent of the floor area of the new extension. Therefore over compensations in the thermal elements in other areas within the property will have to be made to show the CO2 emissions from the existing house along with the proposed extension is no worse when compared to the existing house and an extension whose glazing is within the permitted amount judged against Part L1B of the building regulations.

You will need SAP calculations to find solutions and show compliance.

When you are changing the use of a building, 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. Phone us, if you are unsure if you need them.