This is certainly by far the most common question asked. Check out Andrea’s video explanation above, or read the full explanation here on the right.

The typical budget range is between £100 – £300, that is depending on the difficulty and size of your property. If you also need to have an Energy Performance Certificate (EPC) at the end of it there could be another charge of around £50 to register the EPC on the register. Special discounts would typically be available for multiple dwellings especially if they are of the identical style of design.

Before we get to the differences, this is what you will need depending on your job.

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 computations of pre defined data set of a buildings design that’s put together to show the energy effectiveness of a property. EPC is short for Energy Performance Certificate and it’s a summary statement from the SAP calculations in an simple to comprehend document, which could also be used to sell or rent out a property.

There are really 2 kinds of EPCs. The first is a SAP EPC that is created from building plans where all the elements of the building are known. This will normally be required by building control to demonstrate that a property meets specified targets essential to the building regulations. Building control would also need to see the SAP calculations which illustrates in greater detail whether all the components going into your property conform to the building regulations.

The 2nd sort of EPC is the common one that would be needed for anybody who is selling, or renting out a property. This particular EPC uses what’s called rdSAP, which is short for Reduced Data Standard Assessment Procedure, which is used where specified thermal values of, such as, the walls, roof, floors, etc, are not precisely known on an established property. In this situation assumed thermal values are used depending on the age of your property. This type of EPC would be no use to demonstrate compliance with any building regulations. Sometimes building control would simply ask you to get an EPC, however what they would really need to have are the Sap calculations (which is the data behind the EPC) and the SAP EPC (which is a summary report from the Sap calculations).

Still perplexed, after that phone us for further advice.

These will be the finished set of SAP calculations created once the building has been completed to show 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 demonstrate that the proposed construction, on paper at least, would be compliant with Part L1A.

Unfortunately this is not something that you can do yourself. The calculations need to be done by an On Construction Domestic Energy Assessor or OCDEA, working with approved Government program. The Assessor needs to be approved under one of several accreditation 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)

Every new property require Sap calculations to show compliance with Part L1A (Conservation of fuel and power in new dwellings) of the building regs.

It’s now trendy to get large bi-folding doors, sky lights and large quantities of glazing on new extensions. But with the current building regulations the quantity of glazing can be a maximum of 25percent of the floor area of the new extension. So over compensations in the thermal elements in other parts of the property will need to be made to show that the CO2 emissions from the existing house and the proposed extension is not any worse than the existing house and an extension whose glazing is within the allowed amount judged against Part L1B of the building regulations.

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

For anybody who is modifying 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 checklist is not exhaustive. If you’re not certain whether you require them, then contact us.