SAP is the methodology used to calculate the predicted energy use and carbon emissions for new domestic buildings.  

An ‘As Built’ SAP assessment must be undertaken once work on a newly built or newly converted dwelling is complete. This produces a compliance report confirming that the site will meet energy and carbon emission targets set in Building Regulations- Approved Document L (England) or Building Standards- Section 6 (Scotland), as well an Energy Efficiency Rating and an Environmental Impact Rating, which will be displayed on the building EPC document. 

Most Local Councils initially require the undertaking of an ‘As Designed’ SAP assessment, while the build is at planning stage, to ensure that the design will meet compliance requirements before any work starts.  This allows the design team to ‘test’ the performance of the fabric and HVAC systems and incorporate low and zero carbon technologies, therefore ensuring low energy design.  

SAP 10 is the most recent version of the methodology and must be used for any dwelling which applied for planning after 15 June 2022 (England) or 1 February 2023 (Scotland). 

In England, the assessment compares the performance of the actual dwelling to a target ‘notional’ dwelling. In order to achieve compliance, the actual dwelling must be equal to or better than the target site, under 3 metrics, 

-Target Emission Rate (TER)- the maximum carbon emissions allowed for the dwelling, measured in kg/CO2/m2/ year. This takes into account the carbon emitted from the heating, cooling and hot water systems, as well as lighting, pumps and fans. 

-Target Fabric Energy Efficiency (TFEE)- the energy required to heat and cool a home, measured in kWh/m2/year. This reviews the thermal envelope of the building, taking into account heat loss, ventilation rate, thermal bridging, air tightness and solar gains.  

-Target Primary Energy Rate (TPER)- the maximum allowable amount of primary energy, expressed as kWh/m2/year. This covers energy from the heating and cooling systems, hot water, lighting pumps and fans. 

In Scotland, new dwellings must also show compliance by meeting or exceeding target metrics. There are 2 metrics for Scottish sites, 

-Target Emission Rate (TER)- the maximum carbon emissions allowed for the dwelling, measured in kg/CO2/m2/ year. 

-Target Delivered Energy Rate (TDER)- the maximum allowable amount of delivered energy, expressed in kWh/m2/year. 

Under the most recent Scottish Building Standards, Section 6 (2022), any dwelling which is heated by an electrically powered system, or a Heat Network, is exempt from meeting the carbon standard (TER) but must achieve compliance with the energy rate (TDER).