Westminster Sap Calculation Company

Need Sap calculations for either Part L1A, or Part L1B, we’re here to help you. Give us a call for a quotation on your project.

Get QuoteCLICK TO CALL FREE: 0800 046 7345
Air tightness testing
Water calculations

SAP Calculations in Westminster The 10 Most Typical Questions Asked.

Exactly What Are Sap Calculations

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

Sap Calculations, How Much Are They

This might differ considerably dependant upon the measurements and complexity of the dwelling, but a typical price range would be between £120 – £300. If you also need to have an Energy Performance Certificate (EPC) at the end of it there may be another charge of about £50 to lodge the EPC on the epc register. For several properties of similar types, then discount rates could well be offered.

What Is The Difference Between Sap and EPC

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 buildings design that’s put together to display the energy performance of a dwelling. EPC is short for Energy Performance Certificate and it’s a summary statement of the SAP calculations in an easy to understand document, that could also be used to sell or rent a property.

There are actually two types of EPCs. First is a SAP EPC that is created from building plans where all of the components of the construction are known. This will normally be needed by building control to demonstrate that a property satisfies specified targets essential to the building regulations. Building control would also need to see the SAP calculations which illustrates in detail whether all of the components going into your property comply with the building regulations.

The second form of EPC is the common one that will be needed if you are selling, or renting out a property. This sort of EPC uses what’s called rdSAP, which is short for Reduced Data Standard Assessment Procedure, and is used where specific thermal values of, for instance, the walls, roof, floors, etc, usually are not precisely known on an existing property. In this instance assumed thermal values are used according to 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 for an EPC, but what they would really require 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 give us a call for further information.

What Are As Built SAP Calculations

These are the finished set of SAP calculations produced once the building has been completed to confirm that it is compliant with Part L1A of the building regulations. Prior to the building starting, it ought to have had a set of “Design Sap” calculations to demonstrate that the proposed dwelling, on paper at least, would be compliant with Part L1A.



How To Do Sap Calculations

Unfortunately this is not some thing you can do yourself. The calculations have to be done by an On Construction Domestic Energy Assessor or OCDEA, using approved Government program. The Assessor has to be certified under one of the certification schemes and is also regularly audited to keep their certification.

What Information is Needed For Sap Calculations

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)


Sap Calculations For New Build

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


Sap Calculations For Extensions

It’s now quite fashionable to get large bi-folding doors, sky lights and large amounts of glazing on new extensions. But under the current building regulations the quantity of glazing can be no more than 25percent of the floor area of the new extension. Therefore over compensations in the thermal elements in other areas of the property will have to be made to demonstrate that the CO2 emissions from the current house and the proposed extension is not any 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 need SAP calculations to find solutions and show compliance.


Sap Calculations For Conversions

When you are modifying the use of a building, you will require Sap calculations. {The new dwelling will have to comply with Part L1B of the building regulations.}


Do I Need to have Sap Calculations

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. If you’re not certain whether you will need them, then contact us.


Exactly What Are Sap Calculations

If you are reading this, you’ve probably been recently asked by another person, normally your building control representative, to provide sap calculations for your building project. But you probably haven’t been told what sap calculation actually are and why you need them.

You can either click on the video on this page, where Andreas will shed some light on this, or continue reading.

SAP is short for Standard Assessment Procedure and it is the UK government’s procedure for determining the energy performance of dwellings. Sap calculations are needed to prove your building complies with specified energy targets laid down within the building regs.

As a brief overview, that’s pretty much it.

Sap calculations tend to be needed for 3 reasons
1. For all newly built properties
2. For a dwelling change of use, for instance changing a single family home to residential flats.
3. For a proposed extension having in excess of 25 percent glazing

There are two main targets that the sap calculations are required to demonstrate. Firstly that the dwelling emission rate (DER) and the dwelling fabric energy efficiency (DFEE) comply with certain targets.

The computations will be done by a certified and accredited On Construction Domestic Energy Assessor. There is not any need to visit the property as all of the computations are carried out from the building drawings ,so a good set of plans are very important. Once the calculations are completed, an Energy Performance Certificate or EPC can also be created.

If your sap calculations reveal that your property is not compliant, then your Assessor will give you information on upgrades which can be made to make it so. It is very important to liaise with the Assessor as early on in the project as possible because once the building is completed any non-compliances might be quite costly to rectify.

If you require advice on a project you may have in or around Westminster, or require a quote, call us or fill in our get a quotation form.


Our Services


SAP For Dwelling Change Of Use

  • Reports for Part L1B Compliance
  • Free Advice

SAP For Overglazed Extensions

  • Carbon Emissions Reports
  • Heat Loss Calculations
  • Free Advice

SAP For New Builds

  • Reports for Part L1A compliance
  • Free Advice

What You Can Expect From Us

Trusted & Experienced

Our Assessors are fully certified and accredited with years practical experience carrying Sap calculation in Westminster . We also cover the whole of the UK and can assist on any project nationally.

Reliable & Fully Insured

You will be allocated a dedicated Assessor who is also covered by full professional indemnity insurance of up to £100,000 so you know you’re in save hands.

Prompt Service

We’ll respond to your enquiry within 24 hours. We’ll also help you to deliver your project within your timescale.

Satisfaction Guaranteed

We seek to provide 100% customer satisfaction and look forward to working with you.


Get A Quote, Or Call Us For Advice