SAP and RdSAP Consultation

We at Elmhurst welcome that the Department for Business, Energy and Industrial Strategy (BEIS) announced a consultation on the SAP and RdSAP methodologies in December. We are very supportive of this consultation and will certainly be replying to this, in our usual considered manner.

As the leading experts in this field, we at Elmhurst including our new NHER staff (experts) and members, feel it is essential that we respond to this vitally important consultation.

Within the consultation BEIS state: “The SAP assessment is used for many purposes – including compliance with Building Regulations, and to produce Energy Performance Certificates. This consultation sets out twenty areas of the methodology which are under review and seeks views on proposed changes.”

We have asked our teams, which now include NHER experts to investigate the questions. The Consultation has 20 questions, 17 directly relate to SAP, two to RdSAP and one is an open question on using SAP without a Building Regulation change.

The consultation also highlights proposed changes to RdSAP (which are specified in Appendix S and T) of SAP.

Stuart Fairlie, Head of Technical at Elmhurst clarifies that “the changes proposed for RdSAP are proposed to be added to the current SAP 2012 methodology. The changes suggested for the SAP methodology will be updated in the newly proposed SAP 2016 methodology.”

“We are not aware of any impending new Building Regulations/Standards for any of the regions, so the purpose of the methodology is for guidance only and indicates where the calculation is moving towards, obviously keeping up with both technology, current research, as well as fuel costs and carbon emissions. Interestingly the final question is the possibility of a SAP methodology update without a Building Regulation change, which is a very interesting angle. We at Elmhurst are always keen to see improvements to the methodologies to keep them up to date and relevant.”

Analysis of the Questions:

Proposed SAP Changes: by Jason Hewins – Team Leader, Elmhurst On Construction Support

The consultation presents a total of seventeen questions that will affect the SAP methodology. Many of these are changes to the calculator engine aimed at improving the accuracy of the procedure. These include changes to calculation of lighting demand to a more detailed assessment of the fittings, hot water demand to take into account different types of showers and ventilation rates from open chimneys and flues.

Assessment of Overshading for photovoltaic panel arrays

One key section that has come under review is the assessment of overshading for photovoltaic panel arrays. Currently in SAP options for assessment of overshading are fairly limited and have not been changed since SAP 2005. The consultation proposes to allow use of Microgeneration Certification Scheme (MCS) shade factor data for overshading in place of the existing SAP options. The MCS shading factor is more detailed than the corresponding SAP shading factor as it takes into account sun path, near field obstacles such as chimneys, and far field obstacles such as surrounding buildings. This will be the preferred method of data entry for overshading for Photovoltaic panels for as built stage assessments.

Thermal Bridging

Thermal bridging has also come under review. Currently the DCLG Accredited Construction Details offer a range of junction details for cavity, timber frame, solid and steel frame walls. These details were developed in 2002 and the associated psi values do not vary for different u-values. However research has shown that psi values can differ greatly for the same type of wall with different u-values. As a result of this the Table K1 Approved psi values for ACDs are to be removed and assessors will be encouraged to use more accurate and up to date junction details.

Also currently it is feasible to achieve a higher y-value than the default y-value of 0.15 w/m2k by assessing junctions individually. Assessors could then use the default y-value 0.15 w/m2k to obtain a better but false result. To prevent this practice a new default y-value of 0.2 w/m2k is proposed.

Calculation of overheating risk

An area of SAP that has been criticised over the last few years is the calculation of overheating risk contained in Appendix P. A change is proposed to the data entry for this calculation with the aim of increasing the potential of achieving a higher overheating risk. Also the consultation addresses the wider issue of whether SAP is an appropriate tool for assessing internal temperatures and opinions are welcomed on whether alternative methods of assessment such as dynamic simulation should be considered in future.

Other Proposals

Some of the other proposals include changes to the default efficiencies of heat pumps and solid fuel heating systems. These are based on further studies and changes in the HETAS efficiency calculation procedure.

Finally there is also a nod to new technologies coming to market such as photovoltaic arrays directly heating an immersion element in a hot water cylinder, known as PV Diverters. Also intelligent heating controls and electricity storage in batteries are mentioned and evidence is welcomed to support their introduction into SAP in the future.

Jason concludes: “We also are currently modelling the proposed changes across a number of property types, using different fuels and will let our members know what the likely impact is for the new methodology. This will get to the heart of the issue and explain to the Industry what amendments make to a whole property calculation.”

Proposed RdSAP Changes: by Damien Roberts – Team Leader, Elmhurst Existing Dwellings Support

The following two questions are directly related to RdSAP:

U-values for walls

The proposal is to tweak the U-values of certain types of older walls in E&W, NI and Scotland. The changes are based on some recent research showing that certain ‘older’ (Age band A-E) walls do not lose as much heat as originally assumed. There are tweaks to U-values for Stone, Solid Brick, Cavity as built and filled cavity walls. The most dramatic is older solid walls moving from 2.1 to 1.7W/m2K.  Elmhurst always value empirical data to make energy assessments more accurate, the research shows this and therefore it is right and proper to amend the default positions.

Technology Costs in RdSAP

BEIS are requesting any industry information on the costs of energy efficiency improvement measures  used by EPC s and Green Deal. These were amended in 2014, and they feel that the figures used are likely to be up to date.

SAP Change without a Building Regulation Change

As we know there seems a reluctance to make changes to any Building Regulations in an effort to get “Britain Building Again”; however the downside to this approach is that the calculations provided to home owners in terms of regulation compliance and the Energy Performance Certificate are getting further out of date and less relevant. Furthermore it is also worrying as it will stifle innovation and modern solutions, as these will need to be recognised with the SAP methodology. This could be addressed with a SAP change independent of a change to Targets within Building Regulations.

In Conclusion:

Stuart Fairlie concludes; “Elmhurst has been expecting this consultation for some time and are currently digesting the information very thoroughly. We will keep our members informed of the impact of these changes for both the new build market and for existing dwellings market. As always we welcome improvements to the calculations to keep them up to date and relevant.”

Elmhurst would encourage our members to respond to the consultation, and we will be keeping everyone informed of our expert thoughts over the next couple of weeks, as well and making available our considered response in an open and professional manner.

The deadline is 27th January 2017

Details of the Consultation can be found here:

BRE Information:

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