The Standard Assessment Procedure (SAP) is the official English and Welsh system for rating the energy performance of domestic dwellings. SAP calculations produce a number of different outputs to demonstrate compliance with the Building Regulations Part L1A and are included on the dwelling’s Energy Performance Certificate (EPC).

All calculations are based on standard occupancy patterns and a ‘middle of England’ location. So, two identically built and specified properties, one built on the south coast of England and the other located on the North Yorkshire Moors, will have the same SAP rating, as it would be for any location within the country. The point of SAP is to allow for comparison of properties on a national basis, irrespective of location or occupant. Other assessment methods are available that overcome this crudeness and provide more accurate real-life estimates, but SAP is the minimum legal requirement.

The calculations only consider regulated energy use, which is the energy used for heating, hot water and lighting. Energy used for cooking and appliances are excluded and classed as unregulated energy.

SAP ratings

The full formal definition of the SAP energy rating is – ‘A number between 1 and 100+ based on the annual space heating, water heating and internal lighting costs per square metre for the property, calculated using standard occupancy and location assumptions and deflated three-year average fuel prices’. The SAP energy rating provides the basis for the Energy Performance Certificates (EPCs) required for all new build dwellings at the point of sale, which place the SAP rating on an A-G scale (similar to that used for the energy labels on white goods, such as fridges).

The SAP calculates a rating for the annual energy cost for the dwelling in question, based on the built structure, it’s heating system, internal lighting and any renewable energy technologies installed.

The SAP energy rating scale of 1 to 100+ relates to fuel running costs for the dwelling (not carbon emissions), with the higher the number, the lower the costs. The scale is set so that 100 represents zero energy cost, so a number over 100 would indicate that energy is being exported (from a solar PV array, for example). Remember, however, that this only relates to the energy costs included under the SAP requirements and does not include cooking and appliances, so a dwelling with a score of 100 may still have fuel bills to pay! The SAP rating is adjusted for floor area so that it is effectively independent of the size of the dwelling for any particular built form.

Part L1A of the Building Regulations

A SAP calculation is needed to demonstrate a dwelling complies with Part L1A of Building Regulations and will be required by Building Control. The calculation will check the following areas to ensure compliance:

  • Building fabric meets the limiting fabric parameters detailed in Part L1A as a minimum
  • Building systems meet the limiting system efficiencies and controls detailed in Part L1A as a minimum
  • The predicted dwelling emissions rate (DER) is below the notional target emissions rate (TER)
  • The predicted fabric energy efficiency (FEE) meets the notional target
  • There is not a high risk of overheating

SAP/Part L1A Calculations – Blewburton Limited approach

Blewburton Limited is licensed with Elmhurst Energy to produce SAP reports, Building Control checklists & reports and EPCs for new build dwellings. Prices for individual dwellings typically start from £180 + vat, depending on complexity. Our pricing is a one off fee, with no extras, unless the dwelling undergoes a complete redesign.

SAP calculations for new build properties can be derived from drawings and specifications, rendering a site visit unnecessary.

We recognise that at the early stage of design, not all the information required to assess a dwelling will be available. Nevertheless, as long as the actual dimensions of the building are known, SAP software can be used as a design tool to model a variety of parameters to ascertain the best solution for a particular development. Building Control bodies should ask for a design stage SAP calculation for a property before construction commences!

In all our work, we will offer feedback on potential improvements or concerns we identify. When a design does not comply with Part L1A we seek solutions and make recommendations, such as improvements to U-values through extra insulation or use of alternative products; alterations to boiler specification and heating system control; or the incorporation of renewable/sustainable energy products.

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