SAP calculations

Photo credit: Staunton Manor, Whitecroft Developments Ltd

The Standard Assessment Procedure (SAP) is a stable-state computer model of a dwelling that estimates annual energy consumption.

It is the calculation which generates an Energy Performance Certificate (EPC). SAP calculations, along with an EPC are two of the documents required by building control sign off and they are a legal requirement when a property is sold or rented.

We will:

  • Ensure your project designs and calculations are as energy efficient as possible.
  • Accurately model your buildings’ energy performance to decrease the chance of overspecification in the building design. This will ensure the project is an energy efficient as it can be for the budget.“Accurately modelling this prevents you from spending more than you need to. It’s also an area that will need to be addressed more closely under the new regulations,” says Michael Brogden, operations director at Darren Evans.
  • Support you to design, create and build something that is cost-effective and an efficient use of resources.“We do this by understanding how building physics, energy compliance, and carbon emissions fit together,” explains Michael.
  • Meet your deadlines quickly, giving you the best solution for your project
  • Work on any type of project, from high profile projects, high rise residential buildings to large or small housing developments.

Top tips

  1. Bespoke Psi values (ψ) are critical
    Psi value modelling ensures that the fabric of a building is accurately described preventing the chance of an overspecification elsewhere in the building’s fabric, lighting, ventilation or heating.Under the new Part L 2020 regulations, Accredited Construction Details (ACDs) will be removed so bespoke calculated Psi values or pre-calculated industry values from building product manufacturers will be key.
  2. The new regulations make water heating demand more important
    Water heating demand becomes proportionately more important in the new SAP 2020 regulations as space heating demand becomes proportionately smaller.This change in focus means you need to put in place measures to directly reduce water heating demand.Implementing Waste Water Heat Recovery (WWHR) systems becomes essential.“If you put wet rooms back-to-back, they can share a Waste Water Heat Recovery Stack, which increases the energy efficiency benefit within the SAP calculation. This is a simple way to save money and improve energy efficiency,” says Michael.
  3. Decentralised Mechanical Extraction Ventilation (DMEV) can be a more energy-efficient calculation option over natural extract ventilation
    “There are energy efficiencies to be gained within the SAP calculation through using DMEV as it enables product specific fan powers to be used over generic values improving the calculation efficiency helping to reduce the risk of overspecification,” explains Michael.

Watch out for: 

Accredited Construction Details (ACDs) Generic Psi values available from the Planning Portal are being removed, which will impact your ability to pass the forthcoming Part L 2020 building regulations. If you use default Psi values for heat-loss junctions, it’s likely that you won’t comply with Part L 2020. So, you should either:
  • Find a building product manufacturer who has calculated a set of fabric-specific Psi values. This will need careful co-ordination at construction stage, or;
  • If you use the same construction details project-after-project, it’s more cost-effective to calculate your own set of Psi values. This enables you to better describe in the SAP calculation what’s actually happening in the building, which guards against over-specification.
Get in touch

Next steps

  1. Our SAP assessors are here to answer any questions you have
  2. If you send us your plans, we can offer you detailed advice and quotes
  3. Don’t forget, let us know what you’re trying to achieve as early as possible. Some of the most cost-effective solutions need to be considered in the design phase before construction has started.
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