SAP Calculations (Standard Assessment Procedure) are essential to your building project

What Are SAP Calculations?

Domestic SAP Calculations help you calculate how much energy your home is likely to use, as well as the level of CO2 emissions it will produce.

However confusing they might appear, SAP Calculations are a core element in the design of any residential scheme, and an essential part of existing Building Regulations.

Under Part L of the building and planning regulations in the UK, new homes must have been through an SAP Assessment, and as a result of this, most developers have a working knowledge of their content.

However, first time builders, developers and self-builders are sometimes challenged by the process of SAP Calculations in the building and planning phase.

The role of SAP calculations for buildings is threefold:

  1. To calculate the energy-related costs of a dwelling. The resulting figure is called a SAP Rating.
  2. To evidence compliance with building regulations (Part L)
  3. To generate data required to put together an Energy Performance Certificate (EPC)

A slightly different assessment may also be required when building an extension or conversion. If you are building in Scotland, bear in mind that different requirements apply, so please make additional checks.

SAP is an abbreviation for ‘Standard Assessment Procedure.’ SAP is the single, government-approved system for determining a new home’s energy rating. Companies approved to make SAP Calculations have to be accredited and registered with a certification body.

SAP Ratings make for easy comparison between homes, allowing potential buyers to choose between dwellings having different SAP scores. A SAP Calculation scale runs from 1 and 100, where 100 represents no energy costs at all. The higher a dwelling’s SAP rating, the lower the fuel bills and, significantly in this era of climate change, the lower the emissions of co2.

Dwellings can achieve an SAP assessment rating over 100; however, this would mean they are capable of exporting surplus energy by having solar panels, for instance.

Factors taken into account when calculating energy costs in a SAP Calculation include:

  • Construction of the dwelling
  • The heating system
  • Internal lighting
  • Renewable technologies.

However, it is worth noting that SAP Calculations do not include the energy consumption of household appliances such as ovens, TVs, and refrigerators.

Why do you need an SAP Calculation?

No one is entitled to let or even market property for intended sale unless the relevant builder can demonstrate conforming with an SAP calculation.

SAP matters for other reasons too. An assessor can play an active role in assisting designers and architects in creating the optimum energy profile of new builds – minimising energy use and pushing down carbon emissions.

Proper SAP certification reveals differences in the relative effectiveness of various types of construction and home heating models, which in turn informs delivery to the end-user.

A further critical point concerns the sharing of SAP data. SAP ratings lay bare the energy performance of relative dwellings and are made freely available through the EPC document.

To ‘pass’ the SAP Assessment, a builder must:

  • Quantify the heat retention and solar gain properties of the dwelling
  • Demonstrate the dwelling’s construction quality
  • Evidence of the commissioning of systems
  • Calculate the dwelling’s predicted CO2 emissions

Emissions calculations are critical in SAP calculations

Crucial emissions targets calculate through what are known as DER/TER numbers. Calculations of CO2 emission levels result from a comparison of the Target Emission Rate (TER) and a prediction of the Dwelling Emission Rate (DER). A target rate determines following the application of baseline measurements to a representation of a roughly similar house.

Councils increasingly employ CO2 calculations to meet their sustainability targets and to further energy policy. Providing an accurate SAP Calculation when submitting planning applications to local authorities demonstrates that your new build, extension, or conversion complies with energy efficiency guidance in UK building regulations.

Fabric Energy Efficiency in SAP Calculations

A requirement to assess the Fabric Energy Efficiency (FEE) of all new homes was brought in in England for dwellings built post-April 2014.

FEE does not measure carbon. It records energy requirements in kilowatt-hours per square metre per annum. How effectively dwellings retain heat closely relates to its CO2 emissions — a separate measure subject to compli-ance testing.

Fabric Energy Efficiency is assessed using DFEE/TFEE figures, with targets set in SAP calculations using reference values relating to property size.

How Do SAP Calculations Work?

It is essential that all technical specifications from which SAP inspectors derive their measurements are comprehensively detailed, highly accurate and professionally determined. 

Drawings should be to scale and depict all elevations. From the technical specifications of such elements as ventilation, heating and AC systems, assessors construct models of homes using SAP computer applications. Manufacturers’ databases are then accessed and specific product details incorporated.

Every thermal detail of the building’s fabric is also added as are the details of any renewable or cooling technology.

The length of time it takes to get your application passed depends on your construction timeline. Briary Energy has a target for completion of between 5–10 working days after submission of a request.

A finished set of SAP calculations constitutes a comprehensive, fully-accessible database of building knowledge on everything from heat loss, to fluctuations in seasonal demand.

How Do I Make My Building Pass A SAP Assessment?

Nowadays, starting work before you have a design is challenging. Whereas in the past, architects and developers all but ignored SAP Calculations, changes to SAP in 2005, 2009 and 2014, now ensure that SAP regulatory compliance is much tougher to attain.

Unsurprisingly, given the current climate crisis, and resultant EU and UK environmental policies, control of CO2 emission targets have tightened enormously. A typical new build designed just 5 years ago has a good chance of failing today’s regulations.

One of the most common FAQs on this subject is, ‘Why do some builds fail and others pass?’ There’s no easy answer, but a variety of factors can contribute to a rejection: Boiler size, for example. Or a non-compliant wall junction. Even the thickness of floor insulation on a floor, or the direction in which a house points!

Some factors lie beyond client control – if a dwelling has no connection to mains gas; for example, the owners might have to use oil or gas. Fossil fuels cost more and generate significant CO2 emissions, and because Target Emission Rates are based on mains gas, you may lose out.

How Long Do SAP Calculations Take to complete?

The length of time it takes to get your application passed depends on your construction timeline. Briary Energy has a target for completion of between 5–10 working days after submission of a request.

And if my building fails?

The bottom line? It’s illegal to sell or even rent a property that doesn’t have a valid EPC. It is, therefore, essential that your building passes its SAP and that all SAP calculations are complete before starting any building work. Should the dwelling fall short of building regulation standards, our SAP specialists can offer advice on how to improve.

The longer you leave things, the more you restrict your ability to make changes. And the greater the risk of higher bills, as the range of changes available becomes more limited. We aim to provide comprehensive support and guidance throughout the entire SAP process. Though many companies provide calculations only, we offer customers consultancy services to ensure they have everything they need to pass.

What is SAP calculation?

A SAP rating is the measurement needed to produce a Predicted Energy Assessment and On Construction Energy Performance Certificate. Building Regulations allow a SAP calculation and a predicted EPC to be submitted for new buildings before construction begins.

What does SAP stand for energy?

SAP is ' Standard Assessment Procedure. ' It's the only legal, government-approved method for determining a new home's energy rating SAP assessors must be accredited with a certification body.

Do I need a SAP calculation for an extension?

SAP calculations are often required for extensions, especially if your proposal includes large glazing areas. Building Regulations Part L1b requires new glazing areas to account for no more than 25 percent of new floor area.

How much do SAP calculations cost?

Our SAP Calculations for New Builds and Conversions cost from £50+VAT for one unit and from £30+VAT for each multiple units on one site. Our price includes limitless advice on how best to get the project to meet Part L of building regulations.

What is Part L of the Building Regulations??

Part L is a building regulation that covers new construction schemes, which restricts the use of a dwelling or all other buildings in England. This sets new and existing buildings ' energy efficiency and carbon emissions requirements.

Briary Energy specialise in SAP calculations for:

“Thank you for all of your hard work for this scheme, never said no, never delayed always received on the day of EPC request or the next working day, just totally brilliant at all times”

– Jeffrey Hughes
Senior Technical Manager
CALA Group Ltd

SAP Calculations are carried out during two stages, where communication with the SAP assessor is key to gaining compliance:


Design stage – where you will need to make a submission to Building Control before any work begins

Built stage – once the dwelling has been completed and established

The two submissions of SAP Calculations are used by Building Control to check your compliance in accordance to the related targets.

​​There must be evidence when it comes to your product specification – evidence that the design specification has been met. When you reach the ‘As Built’ stage of SAP Calculations, you will also need an EPC for the dwelling as well.

Why not try our U-Value resource.

SAP Calculations

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