Many people come to us wanting to understand what a SAP calculation is and whether their project needs one. This is a brief explainer for anyone in this position.

In this blog, you’ll learn:

What is a SAP Calculation?

SAP stands for ‘Standard Assessment Procedure’. It is the only government-approved method for calculating the energy performance of dwellings in the UK. They have been a requirement for all newly built dwellings in the UK since 1995 under Part L of the Building Regulations and are necessary in order to produce a Predicted Energy Assessment and an Energy Performance Certificate (EPC). Building Regulations require that a SAP calculation and a Predicted EPC be submitted for new dwellings prior to the commencement of work. 

SAP calculations are not only used to demonstrate compliance with Part L and to produce an EPC, they are also used to determine a SAP rating. The SAP indicates a score between 1 and 100+ to estimate the annual energy-related running costs of a dwelling. The higher the rating, the lower the running costs – with 100 representing zero energy cost. Dwellings in excess of 100 are net exporters of energy. So, the higher the SAP score, the lower the fuel costs and the lower the associated carbon emissions.

These calculations are only necessary for residential properties. In England, the SAP calculations measure two elements: the Dwelling Emission Rate (DER) and the Dwelling Fabric Energy Efficiency (DFEE). These calculations are used to determine a Target Emission Rate (TER) and a Target Fabric Energy Efficiency (TFEE). The DER and DFEE must be lower than the TER and TFEE respectively. 

SAP calculations allow comparison to be made of the energy running costs of dwellings anywhere in the UK. This is achieved as the calculations are predominantly location independent and are based upon a notional standard occupancy that overcomes variations associated with physical location and the differing ways that people use their homes.

Do I Need a SAP Calculation?

Yes, a SAP calculation is required under Part L (England and Wales) of the building regulations for most new build and renovation projects in the UK. These documents are concerned with the conservation of fuel and power. They were first introduced in 1995 but have since been amended several times due to changes in the availability and effectiveness of new and emerging technologies.

Home builders need to gain a ‘pass’ on their SAP calculations in order to meet current Building Regulations. Without a pass, building control will not sign off the development, and the property cannot be let or marketed for sale.

To gain a pass a number of compliance targets must be met in relation to:

SAP calculations are necessary in order to produce a new or up-to-date EPC. An EPC Is required by law to rent or sell a residential property. EPC rates a property between A (best performance) and G (worst performance) across two measures: energy efficiency rating and environmental impact rating. Since April 1st, 2018 it has been against the law to rent a property with an F or G rating in either category. Without a valid EPC you may face fines or be unable to sell or rent your property.

How are SAP Calculations Completed?

SAPs should be completed before the building work starts. In order for a SAP calculation to be undertaken, the client must provide as much information as possible. This includes but is not limited to:

U-values represent the rate at which heat passes through openings/building fabric. The higher the U-value the greater the rate of heat loss.

After this information has been collected, the SAP assessment typically involves 4 stages: 

Stage 1: Design Draft

The assessor uses plans and specifications to create a preliminary assessment:

Stage 2: Design Final

After revisions and agreement on the final design, the assessor produces a report for Building Control with a Predicted Energy Assessment (PEA):

Stage 3: Built Draft

Following construction and an Air Pressure Test (APT), the assessor updates the SAP calculation to reflect any variations:

Stage 4: Built Final

The final SAP calculation is completed, and an EPC is generated based on the actual build:

What happens if my building fails a SAP?

It is crucial that your building passes its SAP, because if it fails it is against the law to rent or sell a property without an EPC. So failing a SAP assessment can delay your project and incur additional costs.

Involving a SAP assessor early in the design process helps ensure cost-effective compliance from the start – they can assist the designer and architect in shaping the energy profile of the dwelling. This then minimises its energy use and carbon emissions and helps to prevent any costly redesign. This becomes more difficult and expensive later in the project issues are addressed because the scope of changes available become more limited. 

How do I make sure I pass my SAP?

Here are some key strategies to achieve a good SAP rating:

  1. Exceed Minimum U-values 
    Minimum U values should be exceeded, not just followed, where possible. If the fabric of the dwelling is well insulated, expensive renewable technologies will not be necessary to get a pass. Design as much insulation into the walls, floors, and roofs as possible. 
  2. Minimise Thermal Bridging
    Heat loss through the junctions with external walls is known as thermal bridging. In order to avoid the assessor using default figures, follow a scheme such as Accredited Construction Details
  3. Energy Efficient Windows and Doors
    Pay attention to the U-values on the opening you are specifying. Get the U-values as low as possible (ideally 1.4 Wm-2K or less). 
  4. Air Tightness
    All new builds require APT on completion and the resulting figure goes into the SAP calculation. Ensure a well-sealed building envelope and conduct pre-test checks. It is important to remember that the more airtight a dwelling is, the better the ventilation system needs to be. This is to prevent the build-up of condensation.

What’s next?

Achieving a high SAP rating can be complex, but it doesn’t have to be. Our experienced SAP assessors can guide you through the process, ensuring your project meets regulatory requirements. We use the latest software and methodologies to achieve optimal energy efficiency ratings for your property. Our sustainability consultants have extensive experience in meeting regulatory requirements – they work hard to go beyond mere compliance with building regulations. Their approach is to significantly reduce the amount of assumed data in each calculation to the bare minimum. This means that our SAP calculations are as accurate as possible. 

If you need support with your own SAP calculationcontact us today for a free consultation. We can discuss your project’s specific needs and show you how our expertise can help you achieve both regulatory compliance and exceptional energy efficiency in your home.

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