The Standard Assessment Procedure (SAP) is DECC's methodology for assessing and comparing the energy and environmental performance of dwellings. Its purpose is to provide accurate and reliable assessments of dwelling energy performances that are needed to underpin energy and environmental policy initiatives.
SAP works by assessing how much energy a dwelling will consume and how much carbon dioxide (CO2 ) will be emitted in delivering a defined level of comfort and service provision, based on standardised occupancy conditions. This enables a like for like comparison of dwelling performance.
SAP was developed by the Building Research Establishment (BRE) for the former Department of the Environment in 1992, as a tool to help deliver its energy efficiency policies. The SAP methodology is based on the BRE’s Domestic Energy Model (BREDEM), which provides a framework for calculating the energy consumption of dwellings. In 1994 SAP was cited in Part L of the Building Regulations for England and Wales as a means of assessing dwelling performance. Reduced Data SAP (RDSAP) was introduced in 2005 as a lower cost method of assessing the performance of existing dwellings.
SAP, RDSAP and BREDEM are used to underpin the delivery of a number of key energy and environmental initiatives, for example:
- the Buildings Regulations for England and Wales and the Devolved Administrations relating to the conservation of heat and power, where SAP is the method specified for assessing compliance;
- HM Treasury’s Stamp Duty exemption for zero carbon homes, for this purpose the SAP model was extended to include appliance energy use;
- National Calculation Methodology, as specified by the Energy Performance of Buildings Directive, SAP and RDSAP are used to produce Energy Performance Certificates;
- Local Authority stock reporting, etc.
SAP quantifies a dwelling’s performance in terms of: energy use per unit floor area, a fuel cost based energy efficiency rating (the SAP rating) and emissions of CO2. These indicators of performance are based on estimates of annual energy consumption for the provision of space heating, domestic hot water, lighting and ventilation. Other SAP outputs include estimate of appliance energy use, the potential for overheating in summer and the resultant cooling load.
The SAP2005 and SAP2009 documents can be downloaded via the following links:
Please note: The Warm Front scheme adheres to SAP 2005 version 9.83
SAP 2009 consultation
As part of the work to produce SAP 2009, DECC commissioned a review of SAP 2005. This indicated that a number of changes would help to improve the accuracy of energy performance assessments and these formed the basis of a subsequent public consultation.
The consultation is now closed but the consultation documents, including a list of the unattributed consultation responses, is on the BRE website.
Future work
This latest, 2009 version, of SAP has been published to support the 2010 Amendment to Part L of the Building Regulations for England and Wales, which is expected to deliver a 25% improvement in new dwelling performance. It also supports the Building Regulations of the devolved administrations; responsibility will be devolved to Wales in 2012.
However, the Department for Communities and Local Government's target that all new homes should be net zero carbon from 2016 represents a significant challenge in terms of accurately and robustly assessing the performance of low-energy dwellings. It is therefore essential to ensure that the compliance assessment tools are able to accurately reflect the actual performance of zero carbon and low energy homes. Working with stakeholders, DECC is therefore minded to review, at the earliest opportunity, all aspects of the SAP to determine its long term suitability to deliver this policy initiative.
The underpinning information, product performance and other relevant data that the assessment tools rely upon must also be produced to a high level of accuracy and reliability. DECC will expect relevant stakeholders to contribute to the achievement of that aim.
The impact of the new financial initiatives
DECC has consulted on the proposal to reward the generation of low carbon and renewable electricity and renewable heat through financial incentives. Potential payments for the energy produced under such incentives may have a significant impact on the cost of energy provision for those eligible homes. These impacts have not been factored into SAP 2009, as they have still to be assessed. Work to consider how they may be incorporated within SAP will be taken forward at the earliest opportunity.
Q&A
Are there any significant differences between the previous version of SAP and SAP 2009?
The most significant change is the move to calculating the energy demand on a monthly basis. The purpose of this is to provide more accurate assessments of energy use across the different seasons of the year. Similarly, the other changes are focused on improving the accuracy of dwelling assessments, particularly low energy dwellings.
Will the new version of SAP produce the same results as the previous?
Because of changes to SAP, such as moving to a monthly based energy calculation and reduced water heating demand, and the assumptions used in relation to Part L of the Building Regulations there may be very small differences in the results compared with those produced using SAP 2005.
What impact will these differences have on the assessment of a) new dwellings, b) Code for Sustainable Homes Level 3, c) existing buildings and d) the production of energy performance certificates?
Any differences that are noticed will not impact on the 2010 Part L Amendment’s requirement for a 25% improvement in the Target Emission Rate (TER), which equates to Code Level 3. For existing buildings assessments are based on the actual construction details, not those assumed for design purposes, so there is no impact. The outputs that SAP delivers for energy performance certificate purposes may differ because of updates to fuel prices and carbon dioxide emission factors.
Why didn’t this version of SAP incorporate more of the proposed changes set out in the consultation?
Most of the changes consulted upon were incorporated with SAP 2009. The use of projected weather data was not take forward, though the weather data used by SAP have been updated. The methodology proposed to calculate CO2 factors was not adopted, the previous methodology was retained.
Why are the CO2 emission factors listed in Table 12 of the SAP document different to those shown in the consultation document?
The CO2 factors listed in the consultation document were for illustrative purposes only, based on the information available at the time of publication. The CO2 factors in the SAP document have been calculated using the latest available data. And, in response to consultation feedback, DECC decided not to adopt the methodology outlined in the consultation document but revert to the methodology used to inform SAP 2005.
Why are we using the 2005 SAP methodology to assess CO2 emission factors?
The consultation responses suggested that there was some concerns about completely moving away from the 2005 methodology at this point. It was therefore decided to continue using the SAP 2005 methodology for producing carbon emission factors based on the most up-to-date information available. Nonetheless, it was recognised that further work was required to examine the difference in carbon savings between distributed generation and grid based generation in terms of transmission losses. This will be considered, amongst other issues, as part of a proposed extensive review of SAP.
Is SAP meant to be a design or compliance tool?
SAP is a compliance tool. However, there is no reason why designers could not use it to predict the performance of different dwelling designs. Given that the assessment methodology and calculation principles are fully set out in the SAP document then software suppliers could easily make a design version available.
Why does DECC need to carry out further reviews of SAP?
It is necessary to periodically review SAP to keep it up dated and fit for purpose. In support of this aim DECC may consider issuing an interim revision of the SAP document, if this was necessary. Such a revision would enable minor changes to be brought into SAP before the next formal revision. It could possibly take account of information from work in progress, for example, field trials assessing the performance of products under installed conditions. Though, Appendix Q remains the principal route for introducing new product performance information in advance of a full revision to SAP. Interim revision would have no material impact on assessments previously carried out under SAP 2009.
Will Reduced Data SAP (RDSAP) be amended?
Reduced Data SAP is not being amended in this revision and RDSAP assessments will continue to use SAP 2005 version 9.83 for the time being. It is anticipated that RDSAP will be revised following the implementation of SAP 2009.