SAP Calculations – the Standard Assessment Procedure

The Standard Assessment Procedure, commonly known as SAP Calculations, is the only official, government-approved system for assessing the energy and carbon efficiency of new domestic dwellings.

What is a SAP assessment?

SAP calculations are a way of rating and comparing the energy and carbon performance of different homes. By making standardised assumptions on consumption trends and behaviour, like-for-like comparisons are able to be made.

SAP calculations predict how much energy a dwelling is likely to consume and how much carbon dioxide the property is likely to output. The Assessment gives ratings on:

– Energy consumption per unit of floor area

– An energy efficiency rating based on predicted fuel costs (the SAP rating)

– An Environmental Impact Rating (carbon output rating)

All the above are calculated based on estimates of annual energy demand from space heating, hot water demand, lighting, ventilation, appliance energy use and cooling systems. From this, the dwelling is then scored out of 100, with 100 meaning zero energy costs and 1 having the highest energy costs.

New domestic dwellings must achieve must achieve the minimum DER (Dwelling Efficiency Rating) prior to the building being signed off for building regulations.

How is a SAP calculation undertaken?

SAP assessors work off of architectural plans, details of constructions and heating, ventilations and air conditioning specifications. In order for SAP ratings to be calculated, drawings will need to be to scale accurate, showing elevations, elevations, floor and site plans.

These plans are then scaled and drawn up and a model of the property is created. The proposed heating, ventilation and lighting systems are added, along with thermal elements and thermal junctions. From here, SAP calculations can be produced that provide information on predicted energy consumption, heat losses, carbon emissions, renewable contributions and more.

When are SAP rating required?

SAP assessments have been a legal requirement for all new-build, domestic properties in the UK under Part L of Building regulations since 1995. As such, most developers are familiar with the assessment procedure. However, self-builders and first-time developer’s understanding may be much lower.

SAP calculations, of sorts, may also be required for conversion and extension projects.

Homes will need to achieve a ‘Pass’ on their SAP calculations in order for the project to meet criteria to pass building regulations. Without this, a property will not be signed off by Building Control and may not legally be listed for rent or sale. As a result, it is advised that SAP scores are calculated and considered at the beginning of project design.

Why are SAP calculations important?

Although a SAP assessment pass is required to comply with building regulations, there are other reasons why it is vitally important to consider your SAP score long before project completion.

Acquiring the services of a qualified and experienced SAP assessor at the beginning of your project to work alongside the designer or architect will shape the energy performance and consumption. Involving a SAP assessor in the design stage of the project will ensure SAP compliance and no surprises at a later date, but ensures that energy consumption and carbon output can be accurately predicted and the running costs of the home minimalised. Also, the customer will be assured of seamless integration of energy technologies when the build takes place.

I addition, SAP ratings highlight the energy performance of the property, either during construction or on completion and form the basis of the dwelling’s EPC (Energy Performance Certificate). An EPC is legally required to be able to market a property for sale or rent and must be presented to potential tenants or buyers at the earliest point.

Important things to remember

A common question from our customers is how do you guarantee passing the SAP assessment. But it’s important to understand and remember that there is no ‘set criteria’ that will ensure a pass, and that each property will have to consider different alternatives to meet the rating need to secure its path.

Although increasing things such as insulation and boiler efficiency are sure-fire ways to increase your chances of a pass, as the specifics of each build is different, as are the requirements to achieve the rating needed. For example, areas without mains gas would have to consider different alternatives. A renewable solution would result in a higher score than gas heating, where as an oil boiler would generate a worse output. This would then carry over into other aspects of the project.

Taking on professional help at the earliest stage of the project will ensure all aspects are considered. An accreddited SAP assessor will help increase the overall energy efficiency of the project, while decreasing carbon output and the cost of the build.

How can GreenGenUK help?

GreenGenUK is fully qualified to provide SAP calculations on new build, domestic dwellings.

We are able to offer SAP assessments on completion of the project, but, more importantly, we work alongside architects to ensure seamless transition from project design, through the building stage and ultimately through the successful passing of the Standard Assessment Procedure.

Thanks to our background and experience working with renewable technologies and energy efficienct products, we are especially well positioned to advise and instruct on how renewable alternatives will impact SAP ratings and the overall energy efficiency and carbon output of the home in question.

For further advise and to see how GreenGenUK can help with your SAP assessments or any other aspects of your project, contact us via one of the followign methods:

Phone us in the office on 0800 093 3299 to speak directly to one of our renewable consultants


Fill out the enquiry form below with your query and contact details and we’ll contact you with further information.