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Sap Calculations Watford

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Sap Calculations, Exactly What Are They

Have building control or even your architect requested you to get sap calculations in Watford. But why do you need them and what are sap calculations anyway? Then continue reading.

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



Watford SAP Calcs For Dwelling Change Of Use

  • Reports for Part L1B Compliance
  • Free Advice

Watford SAP Calcs For Overglazed Extensions

  • Carbon Emissions Reports
  • Heat Loss Calculations
  • Free Advice

Watford SAP Calcs For New Builds

  • Reports for Part L1A compliance
  • Free Advice

What does SAP mean?

SAP stands for Standard Assessment Procedure and it is the UK government’s way of calculating the energy efficiency of buildings. The calculations are necessary to prove your building conforms with specified energy targets laid down in the building regs.

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


When Are SAP Calculations Needed?

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

1. For all newly built homes
2. For a dwelling that’s changed its use, for example 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 be looking at is that the carbon emissions from the property are within set tolerances and that certain components of the property, for example the windows, walls , floors and roof comply with certain thermal targets.

Sap calculations will be done by a certified and certified On Construction Domestic Energy Assessor. There is no need to visit the property because all of the calculations are carried out from the building drawings ,so a good set of plans are very important. An EPC or Energy Performance Certificate is usually produced after the calculations are finished.

Your Assessor can provide you with further advice in the event the calculation show that your building isn’t compliant, as well as explain to you which will be the best improvements to make. It may be expensive if you find out at a late stage in the construction that your building is not compliant. So it’s advisable to liaise with the Assessor as early on in the project as possible.

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


Here we have presented the most frequent questions asked about SAP Calculations in Watford.

Sap Calculations, Exactly What Are They

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

Sap Calculations, How Much Are They

This may differ considerably depending upon the measurements and complication of the property, but an average cost range would be between £120 – £300. If you also need an Energy Performance Certificate (EPC) at the end of it there may be an additional charge of around £50 to lodge the EPC on the register. Discounts would typically be available for a number of properties especially if they are of the same form of construction.

What’s The Difference Between Sap and EPC

Before we get to the differences, here is what you will need 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 calculations of pre defined data set of a properties design that’s created to show the energy effectiveness of a property. An EPC or Energy Performance Certificate is a overview report created from the Sap calculations which produces a SAP rating from 0 to 100. This rating is shown on the Energy Performance Certificate as A the highest to G the lowest. It will also list suggestions that would improve the rating of your property.

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

The second type of EPC is the typical one that will be needed for anybody who is selling, or renting out a property. This type of EPC uses what’s called rdSAP, which means Reduced Data Standard Assessment Procedure, which is used where certain thermal values of, for instance, the walls, roof, floors, etc, are not precisely known on an established property. In this situation assumed thermal values are used based on the age of the property. This particular EPC would be no use to demonstrate compliance with any building regulations. Sometimes building control would simply ask you for the EPC, but 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 of the Sap calculations).

Still confused, then simply contact us for additional information.

What Are As Built SAP Calculations

These are the finished set of SAP calculations created when the building has been completed to confirm that it is compliant with Part L1A of the building regulations. Ahead of the construction starting, it should have had some “Design Sap” calculations to demonstrate that the planned dwelling, on paper at least, would be compliant with Part L1A.



Can I Do The Sap Calculation Myself

No, this is not something that you can do yourself. Sap calculations have to be carried out by an On Construction Domestic Energy Assessor or OCDEA, by using approved Government software programs. The Assessor has to be approved under one of the certification schemes and is regularly audited to keep their qualification.

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

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


Sap Calculations For Extensions

It’s now popular to get large bi-folding doors, sky lights and large amounts of glazing on new extensions. But under the existing building regulations the amount of glazing can be no more than 25percent of the floor area of the new extension. Therefore over compensations on the thermal elements in other parts of the property will have to be made to show that the CO2 emissions from the current house and the planned extension is no worse than the existing house and an extension where the glazing is within the allowed amount judged against Part L1B of the building regulations.

You should have SAP calculations to find solutions and illustrate compliance.


Sap Calculations For Conversions

If you are changing the use of a building, you will require 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 checklist. If you’re not certain whether you will need them, then simply give us a call.


Our Services

What You Can Expect From Us

Trusted & Experienced

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

Reliable & Fully Insured

You will be allocated a dedicated Assessor who is also covered by full professional indemnity insurance 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 seek to provide 100% customer satisfaction and look forward to working with you.


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