How do we ensure the homes we build are truly low-energy? The answer is using The Standard Assessment Procedure (SAP). This standardised method not only evaluates the energy performance of your home but ensures that your new dwelling meets all necessary regulations and standards.
Since it’s such an important aspect of a self-build, it’s important you go into it as informed as you can possibly be. That’s why we’ve put together this quick guide to give you everything you need to know about SAP assessments for your self-build project.
WHAT IS A SAP ASSESSMENT?
The Standard Assessment Procedure (SAP) is the current procedure used by the UK government for assessing the thermal and energy performance of dwellings, as outlined within Approved Document Part L (England & Wales), Technical Booklet F (Northern Ireland) and Technical Standard 6 (Scotland) of the Building Regulations. It is of critical importance to the delivery of the housing and climate change objectives and is required to obtain a Building Warrant.
There are two main uses for this methodology:
- To demonstrate compliance of new homes with the appropriate regulations.
- To generate an Energy Performance Certificate (EPC) for all dwellings, which advise occupants, potential buyers, landlords, and renters of the energy performance of a property.
The current and potential ‘energy efficiency’ and ‘environmental impact’ ratings are expressed on a seven-band scale representing the bands of running costs. Here is a breakdown of the different ratings in a SAP assessment:
A: 92 – 100 SAP points (Excellent)
B: 81 – 91 SAP points
C: 69 – 80 SAP points
D: 55 – 68 SAP points
E: 39 – 54 SAP points
F: 21 – 38 SAP points
G: 1 – 20 SAP points (Very Poor)
As a self-builder, you should always be aiming for the highest score possible. If your proposed dwelling does not score enough points, you may see delays in the project and increased costs.
The UK government is currently looking at replacing the SAP model in 2025 with the new Home Energy Model, but this is still under development. For now, you’ll be focusing on passing your SAP assessment.
WHO CARRIES OUT A SAP ASSESSMENT?
Your assessment will need to be carried out by a qualified SAP assessor early in the design phase. The assessor will review architectural plans and specifications, offering guidance on how to achieve the desired energy rating. The assessor can also review your plans and provide initial calculations and recommendations. Your SAP assessor should be contacted during the planning stages of your project. Early involvement can help integrate energy efficiency measures from the outset.
Your SAP assessor will require information on the construction buildup of floors, walls, roofs from the kit manufacturer as well as their corresponding Psi (Ψ) values. This is a measure of how much heat travels through a particular part of a building that’s prone to thermal bridging, normally at junctions. The higher the Psi value, the more heat is lost, so lower Psi values are better for keeping buildings warm and energy efficient.
Your assessor may also require:
- Glazing type, manufacturer, u-values & g-values of windows, doors, rooflights
- The fuel type, manufacturer and model of your primary heating system
- The manufacturer and model of any hot water systems
- Any secondary heating system
- The manufacturer and model of your MVHR system
- Any renewable technologies found in the home
Once the building is complete, a final SAP assessment is conducted to confirm that the building meets the required standards. The principal contractor will then need to submit photographic evidence back to the SAP assessor to get their final certificate.
DO I NEED A SAP ASSESSMENT? EVEN FOR CONVERSIONS AND EXTENSIONS?
If you are constructing a new residential property, a SAP assessment is mandatory to ensure the building complies with the Building Regulations relevant to you.
For extensions, conversions, or significant renovations, the requirement may vary. It ultimately depends on how much your energy efficiency rating is projected to change. Even if one isn’t required, it is still beneficial to have an assessment to ensure compliance with energy efficiency standards and to improve the overall performance of the building.
WHEN DO I NEED A SAP ASSESSMENT?
Your SAP assessment should be completed as part of a Building Approval application, as you must submit a SAP ‘as designed’ report.
Obviously, there is a lot of detailed information required which you may not have ready prior to submitting the application. In this instance, the SAP assessor will make assumptions regarding makes/models and Psi values, but you will need to have a good idea of the construction type, windows and heating system you intend using.
HOW MUCH DOES A SAP ASSESSMENT COST?
As with most costings, the cost of your assessment will depend on the size of your proposed building. In our experience, it’s best to allocate £300 – 600 for a full assessment and review.
We provide SAP & EPC calculations in-house here at AC Architects as an additional service to make sure that your future home will be as energy efficient as possible. You can find out more about how we work out our costs here.
HOW TO PASS YOUR SAP ASSESSMENT
We know how important a SAP assessment is. Now the question is ‘How do I pass it?’
Here are 5 of the best methods to ensure you get the best score possible:
- Ensure your designer designs to meet (or ideally surpass) the basic regulation u-value back stops.
- Try to obtain the kit manufacturer’s Psi values. Default figures can be used in the SAP calculations, but these are often higher than the actual value.
- Opting for a renewable heating source, such as solar panels or air source heat pumps can make a huge difference to your heating bill and your energy efficiency.
- As your windows and doors will lose more heat than your walls, extra consideration should be given to the materials you choose for them. Triple glazing is a good example.
- Follow the ‘Fabric First’ approach to compensate for the loss through windows and openings through prioritising the fabric of your building.
By following these steps and incorporating the assessor’s recommendations throughout the project, you can achieve a high EPC and an acceptable SAP grade.
Well, what happens if I fail my SAP assessment?
Then it's back to the drawing board! There are many performance parameters that are measured for the SAP so any, or all, of these elements can be improved upon to ensure a pass. A good design team will be there to assist you in this scenario.
SAP VS PHPP: WHAT'S THE DIFFERENCE?
Some confusion arises between self-builders about the role of SAP and the Passive House Planning Package (PHPP) in their projects. These are two of the most commonly used methods for modelling buildings in the UK, but have different approaches and yield different results.
For starters, SAP is a requirement for new-builds in the UK to show compliance with building regulations and the PHPP is a tool used to test the building against the passive house criteria. SAP assessments also have more of a focus on your energy performance and running costs, whereas PHPP in addition to the energy performance is also focused on your Heat Loss Form Factor (HLFF) and your home’s location. The two methods also consider the same elements, such as thermal junctions, in a different manner.
The PHPP model requires a more detailed approach, leading to a longer process but a more accurate presentation of your home’s energy efficiency. The SAP is simplified, and more suited for regulatory compliance rather than optimisation.
Both SAP and PHPP are useful tools, but do not serve the same purpose. They cater to different needs and standards, with SAP focusing on regulatory compliance in the UK and PHPP focusing on designing ultra-low energy buildings globally.
At AC Architects, we often use the PHPP tool at preliminary design stage to inform the design of the building, its form, orientation and areas of glazing and how the building will perform. This PHPP tool helps in those early design decision aiding the planning process and submission of the design that does not need to be changed at later date that may result in delays and additional cost to your project. SAP is then used at later stages once the planning approval has been granted.
You can also continue using the PHPP software that can help you making decisions on levels of insulations, establishing the thermal performance of the windows, ventilation strategy and the specification of the MVHR system.
You can find out more about the role of PHPP software here.
SAP assessments play a vital role in the success of self-build projects by ensuring regulatory compliance and enhancing the energy efficiency of your home.
As energy performance becomes increasingly critical, integrating SAP assessments into your self-build process is not just beneficial but essential. Prioritise energy efficiency from the start, and make sure to let your design team know of your low energy requirements!