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Sap Calculations Wandsworth

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Sap Calculations, Just What Are They?

Have building control or perhaps your architect asked you to get sap calculations in Wandsworth. Why do you need them and what exactly are sap calculations anyway? Then keep reading.

You can click the video recording on this page, where Andreas will shed some light on this, or read on.



Wandsworth SAP Calcs For Dwelling Change Of Use

  • Reports for Part L1B Compliance
  • Free Advice

Wandsworth SAP Calcs For Overglazed Extensions

  • Carbon Emissions Reports
  • Heat Loss Calculations
  • Free Advice

Wandsworth SAP Calcs For New Builds

  • Reports for Part L1A compliance
  • Free Advice

What does SAP mean?

SAP is short for Standard Assessment Procedure and is the UK government’s procedure for calculating the energy efficiency of dwellings. The calculations are required to demonstrate your building conforms with specific energy targets laid down within the building regulations.

That’s more or less it in a quick summary.


When Are SAP Calculations Needed?

Here are most of the reasons you may well be asked for sap calculations

1. For all new homes
2. For a dwelling that’s changed its use, such as altering a single family home to residential flats.
3. For extensions that have more than 25% glazing

The two main areas which the sap calculations will look at is that the carbon emissions from your property are within set tolerances and that certain components of the property, for example the walls, floors, windows and roof comply with certain thermal energy targets.

The computations are done by a qualified and approved On Construction Domestic Energy Assessor. There is not any need to visit the property because all of the computations are carried out from the building drawings ,so a good set of plans are very important. An EPC or Energy Performance Certificate can be produced once the computations are finished.

If the sap calculations show that your property is not compliant, then Assessor will give you advice on improvements which can be made to make it so. It may be costly if you find out at a late stage in the construction that your building isn’t compliant. So it’s advisable to liaise with your Assessor as early on during the project as possible, ideally before any building commences.

If you need advice on a project you may have in or around , or require a quotation, contact us or fill in our get a quotation form. We’re here to help.


Rather than trawl through a entire website to obtain the answers you’re searching for, we’ve given answers to the ten most usual questions asked about SAP in Wandsworth.

Sap Calculations, Just What Are They?

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

Sap Calculations, How Do They Cost

If there are a number of properties with similar types of constructions, then reductions may apply. But typically for a single dwelling the cost will be in the area of £120 – £300. By providing the plans, you will be able to get yourself a fixed price quotation.

What Is The Difference Between Sap and EPC

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 computations of pre defined data set of a buildings design that’s created to show the energy performance of a property. EPC stands for Energy Performance Certificate and it’s a summary report of the SAP calculations in an straightforward document, that can 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 building are known. This will normally be required by building control to demonstrate that the dwelling meets specific targets required by the building regulations. Building control would must also see the SAP calculations which illustrates in detail whether all of the elements going into your property comply with the building regulations.

The 2nd form of EPC is the common one that will be required if you are marketing, or renting out a property. This kind of EPC uses what’s called rdSAP, which stands for Reduced Data Standard Assessment Procedure, which is used where certain thermal values of, such as, the walls, roof, floors, etc, are not precisely known on an established property. In this instance assumed thermal values are used based on the age of your property. This type of EPC will be no good 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).

If you are still perplexed, then call us to get more assistance.

What Are As Built SAP Calculations

These will be the final set of SAP calculations produced after the dwelling has been completed to hopefully demonstrate that it is compliant with Part L1A of the building regulations. Prior to the building starting, it should have had a set of “Design Sap” calculations to demonstrate that the proposed dwelling, in theory at least, will be compliant with Part L1A.



How To Do Sap Calculations

No, this is not some thing that you can do yourself. The calculations must be done by an On Construction Domestic Energy Assessor or OCDEA, using approved Government software programs. The Assessor needs to be certified under one of several accreditation schemes and is regularly audited to keep their certification.

What Info is Required 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

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


Sap Calculations For Extensions

It’s now quite fashionable to have large bi-folding doors, sky lights and large amounts of glazing on new extensions. However with the current building regulations the quantity 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 places of the property will have to be made to show that the CO2 emissions from the existing house along with 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 will need SAP calculations to find solutions and show compliance.


Sap Calculations For Conversions

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


Will I Need 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 is not an exhaustive list. Call us, if you are not sure if you need them.


Our Services

What You Can Expect From Us

Trusted & Experienced

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

Reliable & Fully Insured

You will be assigned a dedicated Assessor who is also covered by full professional indemnity insurance of up to £100,000 so that 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 aim to provide 100% satisfaction and look forward to working with you.


Get A Quote, Or Call Us For Advice