Elmhurst Prepare Response to SAP and RdSAP Consultation

Following the Department for Business, Energy and Industrial Strategy (BEIS) announcement of a consultation on the SAP and RdSAP methodologies back in December, we as the leading experts (Elmhurst and NHER) in this field have been busy investigating and digesting the consultation questions and associated research documentation.

In an effort to keep our members informed of the impact of these changes for both the new build and existing dwellings market, we are summarising the key points from each consultation question. In order to help our members we have written our draft response to each question in terms of the impact on SAP and RdSAP separately.

The information below is a draft high level summary response. We would strongly encourage our members to respond to this important consultation and we hope that this information gives an oversight of our expert opinion in this subject matter. You can access the consultation response here

We welcome any feedback from our members, and have created a form for which you can send your consultation response feedback or suggestions to us (click here for feedback/suggestion form).

In order to continue to be open, honest and vitally independent; we will post our full finalised response, with more detail, before the deadline next week (27th January 2017).

1. Do you agree with the proposal to use the methodology set out in the technical working paper for calculating carbon emission factors and update the figures?


 SAP - Elmhurst agrees with the proposed reduction in CO2 factor for electricity based on the increasing proportion of renewable energy into the national energy generation mix. Elmhurst would be interested to see what the impact of both domestic and foreign nuclear power stations will have on the carbon factor of electricity going forward.

Elmhurst believe CO2 has a greater impact for new build dwellings due to Criterion 1 of AD L1A setting mandatory CO2 standards for regulation compliance when compared to existing dwellings.

 RdSAP -This will have an impact on the environmental rating within an RdSAP EPC which will affect carbon savings. However, the assessment will show a more accurate rating and therefore we support this. It will not affect the SAP (energy cost) rating displayed on the EPC.

2. Should we keep the current set of heating patterns set out in SAP or move to using two heating periods every day of the week? Please provide supporting information for your view.


 SAP - Elmhurst do not agree with leaving heating patterns as they are as we believe SAP should reflect household heating patterns as closely as possible. Whilst this would have a relatively small reduction in space heating demand (around 3%) as the EFUS research shows a move to two heating periods at the weekend then we believe SAP should reflect this.

 RdSAP - If the heating patterns are updated, for the weekend period, this would likely have a significant impact on RdSAP calculations, perhaps more so than new build, due to poorer fabric (energy efficiency) elements within the majority of older (existing) homes. However we can’t model this yet to understand the likely impact. Following similar comments throughout this response, any empirical data showing more accurate representation should be used.

3. Do you agree with the proposal to amend default Distribution Loss Factors for Heat Networks?


 SAP -Accurate assessment of heat loss from distribution pipework is an important part of assessing community/district heating and therefore we welcome any improvements in this area. Elmhurst would like to see more community heating systems added to the PCDF database as this would improve data quality used in assessments. The consultation is suggesting that the Industry uses the CIBSE/ADE code of practice, if wanting to use ‘calculated distribution factor’. For this to work, Industry would have to be familiar with these figures and importantly have them available to SAP assessors at the right time.

 RdSAP -The defaults for community heating appear to be getting worse, and therefore this will affect the RdSAP EPC rating of a home connecting to community heating; however if the defaults are more accurate, we support this proposal.

4. Do you agree with the proposal to change the way that lighting is calculated in SAP?

Yes (with caveat)

 SAP -This is a significant change to methodology and will have a notable impact on SAP/RdSAP assessors.

For new build dwellings we believe this is the correct approach as lighting is becoming a greater part of the energy use of a dwelling as fabric standards and heating efficiencies improve. This approach will also allow different types of low energy fittings to be modelled more accurately when compared with SAP 2012 and earlier. The current approach has been part of SAP for years and a more accurate assessment of lighting energy use is welcomed.

Our concern with this new approach is to ensure industry is aware of the data required by SAP assessors, and that it can be easily obtained for the assessor to complete the SAP calculation. The availability of default data based on EU Energy Rating or energy efficiency class is welcomed.

 RdSAP - In regards to the proposals for RdSAP, Elmhurst believes a simpler method of assessing lighting would be required as this would be a very onerous approach. If Industry like the accuracy these proposals provides, we would suggest that we apply the ‘extended data’ approach where the assessors can continue to use defaults or enter individual fittings if an unusual lighting scenario is encountered. Collecting data on fluorescent lighting, LED’s etc. for RdSAP would mean more time spent on the assessment, but the end result would show a more accurate rating. We must be extremely careful to balance out accuracy versus time spent collecting the data.

5. Do you agree with the proposal to remove the default values in Table K1, review default values as proposed, and recognise Certified Thermal Details and Products schemes? Do you agree with the proposal in due course to amend the default y-value to 0.2?


 SAP -Elmhurst agrees with the raising of the default y-value to 0.2 w/m2k to deter the use of a default y-value where calculated psi values have provided. Very few SAP assessments use this default currently so we do not believe this will have a significant impact but clearly it is more accurate for a dwelling to use calculated psi values and lengths rather than a y-value that does not alter for different dwelling types.

Elmhurst also agree with the removal of the DCLGs Accredited Construction Details for the reasons specified in the consultation. One concern is that industry is heavily reliant on the current ACDs so the alternatives available to them must be well communicated. SAP assessors/accreditation schemes can take a lead on this and inform their clients in advance. Elmhurst would welcome functionality where assessors could pick approved junction details from a database incorporated into SAP software.

Elmhurst also agrees that the current Appendix K Default psi values should be amended. These should be sufficiently conservative to stimulate industry in regards to using calculated construction details to gain the performance benefit associated with them.

Finally despite thermal bridging being a part of SAP since SAP 2005, as an accreditation scheme Elmhurst regularly hear from our members that industry fundamentally does not appreciate or understand the impact of thermal bridging. Many assessors have raised concerns of enforcement and there are doubts in regards to local authorities or BCBs checking details are correct during the build process and correlate with the details used in the SAP assessment.

 RdSAP -This would have little impact on an RdSAP assessment other than showing a more accurate final rating.

6. Do you agree with the proposals to adjust U-values and Ψ-values for elements next to unheated spaces?


 SAP -For adjusting u-values Elmhurst agrees that the shelter factors should reflect current building practices. There would be no difference to the assessor as the same scenarios remain therefore we support this change.

Elmhurst would like to use this opportunity to raise our members’ concerns around the procedures for addressing roof voids in a room in the roof where the insulation is contained entirely within the pitch of the roof. Currently the SAP Conventions require the uninsulated wall to these roof voids to be treated as a heat loss wall, with the u-value multiplied by a factor of 0.72. This is confusing for assessors as clearly most, if not all, of the heat from the roof room will travel through this uninsulated wall construction into the roof void, and therefore the thermal envelope is located at the rafters. Elmhurst recommends the procedures for calculating room in the roof is adjusted to “include all volume within the insulated thermal envelope of the dwelling”.

The procedure for sheltering psi values is very complicated for relatively little change in regards to the overall SAP rating. Since this was introduced in SAP Conventions v6.0 our members have expressed concerns with the detail and time required to take this approach as the thermal bridging data entry is already onerous.

 RdSAP -The defaults that RdSAP currently uses for garages, corridors, stairwells etc. do not provide a sufficient reading for potential heat loss. This change would provide a more accurate assumption and overall rating.

7. Do you agree with the proposal to change the default U-values for walls for existing buildings in RdSAP?


 RdSAP -We agree with the proposal 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.

We understand that the wall U-values are an important factor in the assessment of any home, and as such this will make an impact. It may mean that some properties that are currently F or G rated ‘may’ move up a band. This is particularly important for the private rental market where landlords are affected by the current MEES policy, which will effectively mean that rental home must not be adversely cold and costly to run for their tenants (the policy requires them to achieve an E or higher).

We at Elmhurst value the research and empirical data, and any attempt to make RdSAP calculations more accurate is most welcome and should be supported.

8. Do you agree with the proposal to amend the hot water methodology in SAP?


 SAP -Elmhurst generally agrees with improvements to the hot water calculation methodology where the accuracy will be improved. Elmhurst agree that shower type can have a notable impact on the energy use of a dwelling and the methodology should be updated to better reflect this. Elmhurst note that the data entry for this in SAP assessments will ask for a flow rate. Industry needs to be aware that assessors will require this data and if it not forthcoming defaults will be used which will harm compliance.

 RdSAP -This would have little impact on data collection for RdSAP, as it is already requirement to tally the number of baths and showers and state when solar water heating is present. The changes will more accurately reflect the performance of a dwelling.

9. Do you agree with the proposals to change the questions in the assessment of internal temperature in summer (Appendix P)?


 SAP -Elmhurst agree with the proposals to amend Appendix P.

Due to the change in building regulations resulting in higher levels of insulation and air tightness, Elmhurst believes the overheating assessment is becoming more important. Overheating is one of the largest factors in regards to the living conditions within a dwelling, and as an accreditation scheme Elmhurst has heard accounts of temperatures, within flats in particular, being extremely high. The methodology within SAP should accurately reflect the correct risk of overheating as currently some assessors are manipulating the results in order to achieve a compliant calculation.

Elmhurst questions whether SAP is an appropriate tool for assessing overheating. The options in SAP are still relatively limited and dynamic simulation modelling can offer a much more through assessment of risk. Elmhurst would request SAP allows for data calculated in accordance with the approved procedure by a different software package to be entered where appropriate.

 RdSAP - There will be no impact for RdSAP.

10. Do you agree with the proposal to amend the treatment of Mechanical Ventilation Systems in SAP?


 SAP -Elmhurst agrees that the testing method for DMEV should be altered to better reflect installed conditions.

 RdSAP -There will be no significant impact for RdSAP.

11. Do you agree with the proposal to change the assumed air flow rate for chimneys and flues in SAP?


 SAP -Elmhurst agrees with the proposed changes to air flow rates. Open chimneys/flues are rarely used in new build dwellings so this will have a greater impact on RdSAP.

 RdSAP -This will not affect a data entry for an RdSAP assessment as there is already a requirement to enter the flue types and number of open fireplaces. However the final SAP rating will be slightly worse than current EPC’s.

12. Do you agree with the proposal not to alter assumptions on storage heating secondary fractions in SAP?


 SAP -Elmhurst agrees that the storage heating fraction should remain as currently in SAP.

 RdSAP -We agree that the assumptions should not be changed as the evidence provided supports the current fractions used.

13. Do you agree with the amendments proposed to solid fuel heating efficiencies?


 SAP -Elmhurst agrees with the proposed amendments to solid fuel appliance efficiencies. An observation from speaking to assessors is that the solid fuel appliance industry uses lots of different test methods when calculating efficiencies and assessors sometimes struggle to obtain the SAP efficiency for SAP calculations. The HETAS website is a good resource for SAP efficiencies that could be more directly referenced from within SAP. Ideally the PCDF would be updated to include room heaters.

 RdSAP -The data collection for RdSAP would not be affected. However, changes to efficiency values will have a varied affect on the final SAP ratings, but again if more accurate due to research then this is welcomed.

14. Do you agree with the proposal to amend the procedure for determining overshading of solar PV installations?


 SAP -Elmhurst agrees in regards to increasing the efficiency of the methodology in regards to overshading.

 RdSAP -RdSAP will not be affected as this is only for inclusion in SAP. 

15. Do you agree with the approach to adjust the carbon savings where solar PV electricity is used in the home to heat water or where it is put into battery or other storage? Do you have a view on the correct export tariff for PV electricity exported to the grid? Do you have ideas on how solar thermal space heating, or storage of solar PV or hot water through a battery or other medium can be modelled?


 SAP -As an accreditation scheme Elmhurst regularly get enquiries about how to model PV diverters therefore the inclusion of PV diverters, solar thermal space heating and battery storage would be a welcome addition to SAP AND RdSAP.

 RdSAP -Currently this is not possible to reflect within RdSAP. If research suggests the changes would support greater accuracy, we would welcome the inclusion.

16. Do you agree with the proposal to provide a series of seasonal efficiencies for boilers on the Product Characteristics Database dependent on the controls they use and the design flow temperature of the system?

Do you agree with the proposed change to the Energy Balance Validation method?


 SAP -Elmhurst agrees that boilers should have a range of efficiencies based on the flow temperature and/or controls that are used. Elmhurst agrees that the Energy Balance Validation method be amended to better reflect the part load efficiencies.

 RdSAP -This will not affect the data collection for RdSAP, but we would welcome changes that would show greater accuracy in heating system efficiencies.

17. Do you agree with the proposal to amend the default values for some heat pumps based on evidence from RHPP field trials?


 SAP -Elmhurst agrees with the proposed changes to default heat pump efficiencies based on the RHPP trials. This would only affect heat pumps with a flow temperature of <35° i.e. serving underfloor heating that are not on the PCDF.

 RdSAP -Heat pumps within RdSAP do not generally score as well as many people expect, and therefore we would welcome improvements to the default values. This would not have an impact on the data collection for assessors, but again would give people more accurate assessments of their homes. 

18. Do you have any evidence on the technology costs used in RdSAP?


 RdSAP -As consumers read RdSAP EPCs or Green Deal Assessments they are provided with guidance on ‘indicative costs’ for measures. These figures are obtained from the Product Characteristics Database (PCDb). The difficulty with this, is that labour rates are in practice highly variable and as such ‘ranges’ are provided with a lower and upper figure – they are supposed to be used only as a guide for consumers, to give them a flavour of whether the measure is a low, medium or high cost measure.

Elmhurst do not have any empirical data to suggest these figures need amending. According to the consultation paper these figures were amended in 2014 during the Green Deal process.

As the figures are read from the PCDb directly by the software, there is no reason that these figures can’t be amended as and when information is presented to BEIS that makes them more accurate.

19. Do you have any evidence to update the assumptions that SAP makes about heating controls?


 SAP -Elmhurst do not have any information however we would welcome the incorporation of innovative heating controls into future versions of SAP.

 RdSAP -From an RdSAP perspective there is no evidence currently available.

20. Can you provide any evidence on the cost and benefits to business of revisions to SAP independent of changes to any particular set of Buildings Regulations?


The main benefit of updating the methodology to SAP2016 without a Building Regulations change e.g. the Target Emission Rate being changed, would be that the calculations provided to home owners were more accurate and up to date. Furthermore the calculation would also be improved because innovation and modern practices could be further recognised within any updated SAP methodology. In summary the carbon and costs calculations and the Energy Performance Certificate produced during the process, which is used to sell the property are better, more accurate and relevant.

At the moment there is appears to be an unwillingness to update Building Regulations in relation to energy efficiency, in a move to ‘Get Britain Building’ again. However, the downside of this approach is that it holds innovation back. To continue to use SAP2012 methodology indefinitely stifles innovation, and makes the outputs to the home owners out of date and not particularly useful. We at Elmhurst always welcome continuous improvement and betterment of energy efficiency in buildings. We think that the benefits of this outweigh any negatives.

We want the calculations and EPCs to be as relevant and as correct as we can as an industry make them useful for members of the public.

Here at Elmhurst we welcome the consultation, we are hugely supportive of the research and empirical data undertaken; as they all contribute to a refinement of the methodology and as such will result in more accurate and relevant EPCs. We are however very mindful that the accuracy improvement must be balanced with the fact that the information required is available and also not overly complicated in terms of time and effort energy assessors must undertake in order to use this new information.

Details of the Consultation can be found here:


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