SAP Calculations

SAP Calculation
Some aspects of a building that are measured to gather data to produce a SAP Calculation

As part of the Building Regulations in England, Wales and Scotland, every new-build dwelling is required to comply with regularly updated energy efficiency standards. For a residential building, a Standard Assessment Procedure (SAP Calculation) is carried out to show compliance.

Our Elmhurst accredited OCDEA SAP Calculation experts review your building plans with the proposed specification to compare your building’s expected carbon emissions against the target. The data from the calculation is used to produce an Energy Performance Certificate (EPC), which is needed to sell or rent the new build property. Prices for this start at just £121.00.

A good time to engage our services to carry out a SAP Calculation for you is once you’ve received planning approval before work begins on site. This gives our SAP experts the best opportunity to offer solutions to meet compliance if your proposed specification does not meet the carbon emission target.

We work closely with local authorities, property developers and self-builders to understand their requirements and have a good level of experience in producing accurate SAP calculations. We have in mind the bigger picture when producing your SAP, and if we think you are over-committing in specific areas, we’ll notify you and show where you can save yourself money.

To help your design achieve compliance we work from a fabric first modelling perspective as it is in our experience that greater cost savings can be made in terms of materials and labour using this approach.

For example, savings can be made by using a low emissivity foil based cavity wall insulation when compared with full cavity fill with rockwool. Although this is more expensive from a materials point of view and a bit more labour intensive to fit properly, it allows a developer more space to offer a potential home buyer as the cavity can be made smaller. More space obviously means that a higher premium can be charged for the dwelling. This higher premium is significantly higher than the small uplift in the cost of the lower emissivity foil cavity wall insulation.

There are other tips and tricks that we have learnt over time and include the following as guidance:

The early bird catches the worm!

Get a SAP calculation done as early on in the design process as possible. The earlier a SAP calculation is carried out, the more options you will have to demonstrate compliance with building regulations. Additionally, it can prove to be costly to improve a specification once work on-site has begun.

Low energy lighting (LEL).

For a new build, the minimum requirement is that 75% of internal lights are low energy. By fitting all low energy internal lights will help you are increasing your chances of passing an SAP assessment.

Fabric first.

Did you know that heat loss through fabric accounts for the largest amount of heat loss for most dwellings?

To reduce heat loss, you can reduce u-valves by increasing the amount of insulation and the configuration of insulation, air space, type of internal blockwork and method of fixing internal plasterboard and finishing. All of which improves thermal performance and gives your design a better chance of complying.


It is increasingly possible to find windows with u-valves as low as 1.0. We have also learnt that a BFRC certified window can offer substantial heating improvements as well as increasing the chances that your design will comply.

Air pressure test.

A more airtight dwelling, the better it performs thermally. Most builders can achieve a rate of 5m3/hm2, but consider carrying out pressure testing, too. These can offer advice on how to build an airtight dwelling effectively.

Thermal bridging.

We recommend using bespoke psi values for all or some junctions as they can be a cost-effective way of improving thermal performance, helping you achieve a low air pressure test.

Developers should follow the generic ACD guidance. This allows for an improved psi value to be used in the SAP calculation. However, there are a variety of bespoke psi values which are calculated by manufacturers of building products, trade bodies, retailers etc.

Heating controls.

As standard, most properties with require the following as a minimum:

  • Programmer
  • Thermostat
  • Thermostatic radiator valves

Larger properties – over a floor area greater than 150m2 – will require a time and temperature zone control. However, you can involve advanced controls. These could be a delayed start thermostat or a weather/load compensator – both of which offer a significant benefit.


It may look like a bit of a mouthful and something that you may have only considered for PassivHaus and super Eco dwellings but these systems, although expensive to buy and install are quite simply epic and help a great deal towards compliance.

This WWHRS (Waste Water Heat Recovery System) basically transfers the wasted hot water from the shower drain back into the water feeding the boiler or hot water cylinder thus needing less energy to heat it to its useful temperature. This means that energy is being saved.

The same goes here – the FHGRS (Flue Gas Heat Recovery System) takes heat from the flue which would otherwise be wasted and feeds it back to pre-heat the water going into the boiler. Less energy is therefore used to heat the water to its useful temperature. This means that energy is being saved.

Renewable energy.

Solar panels, solar water heating, wind turbines and even hydro power can be incorporated into the SAP assessment.

Contact us here for a competitive quotation for your SAP Calculation. Our prices range from £121.00 to £348.00


07867 787672



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EPEC Ltd is a private company limited by shares with its registered office at the above address registered with companies house on 2nd July 2018.

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