SAP Calculations

SAP (Standard Assessment Procedure) calculations are energy calculations that predict the energy performance and carbon emissions of a new dwelling.

SAP will look at several categories for the assessment such as:

• Insulation values through the walls, floor and roof
• Solar gains through windows and roof lights
• Air tightness (uncontrolled air leakage causing cold draughts)
• Thermal bridging (heat loss through junctions such as where the floor meets the wall)
• Boiler efficiency and fuel used to power the heating and hot water
• Ventilation fan efficiency and power used
• Low energy lighting
• If required, renewable energy and other low carbon technologies

Using a combination of the above and using architect’s drawings to measure from, the SAP calculation can predict energy consumption and carbon emissions associated with the proposed dwelling.

The software will then set a target for energy efficiency and carbon emissions. The SAP calculation must have lower energy demand associated with space heating. This is the Fabric Energy Efficiency (FEE) and have lower carbon emissions than the target set.

If you are building a new house or houses, then each dwelling needs a SAP calculation to demonstrate that they limit carbon emissions in line with ‘Approved Document Part L1A 2013’ of the Building Regulations.

The SAP calculation should be used to help determine insulation thickness, boiler efficiency, window area and so on, to collect passive solar gains and retain heat to minimise space heating.

At Low Carbon Box, we use the SAP calculation process at the planning stage to help determine the outline specification, allowing the design team to set the cavity width before detailed drawings are carried out. This reduces time and cost for the project team.

Every house is different, but depending on the size of the property (whether it is detached or semi-detached) and the boiler used, then we can generally predict what is required to pass a SAP calculation.

Why not try out our in-built tool to get an idea of a specification that may pass for your new house. Please click here to go to the tool

We have carried out over 10,000 SAP calculations throughout England for a wide variety of clients, from one-off self-build houses to larger housing developments with 300 houses.

Our lead assessor is an on-construction domestic energy assessor (accredited with Elmhurst Energy) with an MSc in Energy & Sustainable Building Design and over 20 years experience in Architecture. Our advice and service is geared around providing solutions for our clients, helping them achieve their goals and input our significant experience to make the process easy, whilst using materials and systems that are readily available.

We break down the service as follows:

• Provide initial advice on a suitable specification for the proposed dwelling(s)
• Provide sample SAP calculations with further detailed specification feedback
• Once the working drawings are completed, we finalise the design stage SAP calculations and issue for submission for approval by Building Control
• Monitor changes during construction that may affect the SAP calculation
• Provide final as-built SAP calculations upon completion, taking into account any changes
• Provide a final EPC (Energy Performance Certificate) for the completed dwelling
• Provide free water calculations
• Provide discounted site services including air tightness testing and extractor fan testing