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

This may can vary considerably depending on the size and complication of the property, but a typical budget would be between £120 – £300. Should you also need to have an Energy Performance Certificate (EPC) at the end of it there could be another charge of about £50 to lodge the EPC on the national register. Reductions would typically be available for a number of dwellings especially when they are of the same style of structure.

Before we get to the differences, here 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 computations of pre defined data set of a properties design that’s put together to demonstrate the energy effectiveness of a dwelling. EPC is short for Energy Performance Certificate and it’s a summary statement from the SAP calculations in an simple to comprehend report, which could also be used to market or rent a property.

There are really 2 kinds of EPCs. The first is a SAP EPC that is created from building plans when all of the elements of the building are known. This would normally be needed by building control to show that the dwelling complies with specified targets essential to the building regulations. Building control would also need to see the SAP calculations which shows in detail whether the many elements going into the property comply with the building regulations.

The second variety of EPC is the standard one that will be necessary if you are marketing, or renting 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, for example, the walls, roof, floors, etc, are not precisely known on an existing property. In this case assumed thermal values are used based on the age of the property. This sort of EPC would be no good to show compliance with any building regulations. Sometimes building control would simply ask you to get an EPC, but what they would really need to have are the Sap calculations (which is the information behind the EPC) and the SAP EPC (which is a summary report from the Sap calculations).

Still perplexed, after that phone us for additional assistance.

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

Unfortunately this is not some thing you can do by yourself. Sap calculations need to be carried out by an On Construction Domestic Energy Assessor or OCDEA, by using approved Government software programs. The Assessor has to be certified under one of the accreditation 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 Sap calculations to show compliance with Part L1A (Conservation of fuel and power in new dwellings) of the building regs.

It’s now popular to get large bi-folding doors, sky lights and large quantities of glazing on new extensions. However with the current building regulations the amount of glazing can be no more than 25percent of the floor area of the new extension. So over compensations on the thermal elements in other places of the property will have to be made to demonstrate that the CO2 emissions from the current house and the planned extension is no worse than the existing house and an extension whose glazing is within the permitted amount judged against Part L1B of the building regulations.

You need SAP calculations to find solutions and demonstrate compliance.

For anybody who is modifying the use of a dwelling, you will require 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 unsure whether you need them, then phone us.