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Sap Calculations Wandsworth

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Sap Calculations, Exactly What Are They?

For anyone who is reading this article, you have probably been recently requested by someone, typically your building control official, to supply sap calculations for your building project.

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



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 stands for Standard Assessment Procedure and is the UK government’s means of determining the energy performance of properties. Sap calculations are needed to prove your building conforms with specified energy targets laid down in the building regs.

That’s basically it in a simple summary.


When Are SAP Calculations Needed?

Sap calculations usually are required for three main reasons

1. For all newly built homes
2. For a dwelling that’s changed its use, e.g converting a commercial building to residential flats.
3. For a planned extension having in excess of 25 % glazing

The two main areas which the sap calculations will be looking at is that the carbon emissions from the property are within set tolerances and that certain elements of the property, such as the windows, roof, floors and walls comply with specified thermal targets.

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

If the sap calculations reveal that your property isn’t compliant, your Assessor will give you guidance on upgrades which can be made to make it so. It might be expensive if you realise at a late stage in the construction that your building is not compliant. So it is best to liaise with your Assessor as early on during the project as possible, ideally before any building commences.

Should you require guidance on a project you could have in , or simply require a quotation, give us a call or fill in our get a quotation form.


Rather than trawl through a whole website to find the answers you’re trying to find, we’ve provided answers to the ten most common queries asked about SAP in Wandsworth.

Sap Calculations, Exactly What Are They?

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.

What Is The Cost Of Sap Calculations

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.

What Is The Difference Between Sap and EPC

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.

What Are As Built SAP Calculations

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.



How To Do Sap Calculations

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.

What Information 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

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


Sap Calculations For Extensions

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.


Sap Calculations For Conversions

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.}


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


Our Services

What You Can Expect From Us

Trusted & Experienced

Our Assessors are fully certified and accredited with several years practical experience carrying Sap calculation in Wandsworth . We also cover the whole of the UK and can help on any job 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 which means 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.


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