Elmhurst responds to survey on the future of SAP and RdSAP

Elmhurst has released its response to the survey on the future of SAP and RdSAP. The article below outlines the different points of the survey followed by Elmhurst's response underneath. 

Please note: the survey has been extended to Friday 11th Dec to submit your response

5. Metrics

These are potential metrics which SAP could use. Could you please indicate whether, in your view, they should be key metrics, secondary metrics or whether SAP should report them at all?

Potential metrics 

Key Metric

Secondary Metric

Not a metric SAP should use

Energy consumption

(delivered energy/Energy Use Intensity)

x

 

 

Primary Energy

x

 

 

Carbon Emissions

x

 

 

Energy running costs

x

 

 

Space heating demand

x

 

 

Peak Demand

x

 

 

Proportion of electrical demand which can be 'shifted'

x

 

 

Renewable energy generation

x

 

 

Overheating risk

x

 

 

Elmhurst's response:

SAP can indeed calculate all of these metrics, the question appears to be guided by what metrics that Building Regulations may use in the future. We at Elmhurst would advocate that all the calculation is made available to all, so that the right metric(s) can be used for the right reason. SAP is not just used for new build. So it is very important to display all the metrics, this way and particular policy or best practice can choose the appropriate metric whether to drive fuel bills down, reduce energy, or reduce carbon emissions.

6. Target setting

Please indicate your preferred option for target setting:

  • Similar to currently i.e. comparing the performance of the dwelling with that of a notional dwelling which is defined by SAP and which has the same orientation and shape as the actual dwelling.
  • Similar, but with significant changes to the notional dwelling. Please detail in the comments.
  • The target should not use a notional dwelling anymore; it should be based on a set of absolute numbers (e.g. Energy Use Intensity in kWh/m2/yr)
  • Not sure

Additional comments, justification or supporting evidence

Elmhurst's response: 

As above we believe this is a question for building regulations as SAP can do whatever option is chosen.

7. Whole house retrofit

Please indicate your level of agreement with the following statement

SAP/RdSAP should become a tool for deep whole house retrofit of existing homes.

  • Strongly agree
  • Agree
  • Neither agree nor disagree
  • Disagree
  • Strongly disagree
  • Not sure

Additional comments, justification or supporting evidence

Elmhurst's response: 

SAP and RdSAP are the Governents approved national calculation methodology for the energy assessment of existing home. The methodology is over 25 years old, and has had many updates over the time to keep up with new technologies and data.

We therefore strongly agree that they are indeed the correct tool to use on the UKs homes. The main issue with these is that the underlying methodology needs to be kept up to date. The fact that we are using SAP2012 still in 2020 and soon to be 2021 is why the methodology gets criticism. We need regular updates to keep up with fuel prices, carbon emissions and invocation and technology.

We at Elmhurst lobbied that RdSAP is the correct tool for assessing existing homes, we also pushed that to model the home at the coordinator stage of Pas20235 that the data should be exported to SAP. The advantages are that the RC or the designer can utilise more fields, mostly around thermal bridging, air testing score and if necessary community heating.

RdSAP appears to get criticism mostly down to in our opinion a lack of understanding of what is does, for PAS2035 whole house retrofit, RAs collect all window area details above and beyond a normal assessment. Most issues come because people see the output the REPC describe elements of the house with words like ‘assumed’ and ‘defaulted’; this is very unhelpful. What it actually means is the energy assessor on site has identified the age of the fabric element the type of wall and the thickness of the wall , and the Uvalue ‘defaulted’ is that from the building regulations at the time. If a Uvalue exists for the element (say wall) this can be entered into RdSAP, using the documentary evidence.

The whole house retrofit will use the correct defaults, and if they are improved then the design will specify the new Uvalue and this can be inserted to obtain a better score for the home.

RdSAP and SAP have thousands of suitably qualified, an accredited members who cover the whole of the UK. They have approved conventions and have a quality assured framework surrounding them to ensure that the quality of their outputs are high.

As said before most people who criticise the methodologies do not understand that they are asset ratings and are therefore not occupancy models; which is why inside PAS2035 we at Elmhurst pushed for the use of the occupancy part of SAP so that not only was the home (the asset) assessed, but also the prediction of energy, carbon and cost was adjusted by the people in the home. Again RdSAP and SAP already have the occupancy model within the nationally approved calculation methodology. It is just that the occupancy part is not used for sales and rental, but is advocated for in whole house retrofit.

 8. A tool for retrofit?

Several options are potentially available in order for SAP/RdSAP to become a tool for deep whole house retrofit of existing homes.

For suggestions related to RdSAP default values, see Q9.

Please indicate your level of agreement with the following options. Feel free to comment on these options or provide additional suggestions in the comments box:

 

 

Strongly agree

Agree

Neither agree/disagree

Disagree

Strongly disagree

Introduce an evaluation of the possible “end goal” representing a low-carbon deep retrofit, even if the regulatory target is different at that point.

 

X

 

 

 

 

Introduce prompts to encourage a whole house approach e.g. automatic “have you reviewed the ventilation?” if insulation or airtightness is improved.

 

X

 

 

 

 

Take better account of airtightness and associated improvements

 

X

 

 

 

 

Elmhurst's response: 

SAP and RdSAP can again perform all the functions listed here. The PAS2035 approach was to allow the owner to decide what their ‘end goal’ is. Should this be the lowest fuel bill, the least amount of carbon emissions, the lowest amount of energy; or indeed a combination? Regulations are separate from the methodologies and if government were to suggest low carbon goal, then simple set this in the particular policy.

Again Ventilation is thoroughly covered in PAS2035 approach, and SAP and RdSAP can adequately cope with these requirements

As before if the assessment is as started in PAS2035 exported to SAP then the pressure test figure can be used to show improvements. It is also if required relatively straight forward to add the pressure test figure into RdSAP if this was found to be useful.

9. Default values in RdSAP

Do you have evidence related to the current approach to default values in RdSAP e.g. evidence that some of the default values should remain the same, or that some default values should change, or that some parameters should become specific users inputs rather than defaults?

Elmhurst's response

We strongly believe that the right balance is already evident in RdSAP, accredited assessor follow the correct guidelines in using the defaulted Uvalues and values if there is no documentary evidence on site available. If they are available then assessors can enter them overriding the age appropriate defaults. This is sensible and pragmatic and works. We need to encourage building owners to have access to good documents, which allow them to use these in the future to obtain more accurate assessments of their homes. Building Log books (passports) should always be available following good quality retrofit work (e.g. data-warehouse) thus this can be the starting position for the next energy assessment.

10. A use for SAP outside of building regulations?

It is considered that, for the purpose of producing fair and robust assessments for building regulations and asset ratings (i.e. EPCs), some degree of normalisation in a dwelling’s energy assessment is required. However, it could be possible to enable the use of SAP where, for non-regulatory purposes, users would be able to modify some of the inputs (e.g. occupancy); they may also test scenarios such as future climate, or ranges of possible U-values (e.g. on existing buildings where current performance may be uncertain) etc.

If such a function was available, do you think it would be of use to you and/or the wider industry?

  • Yes, very much
  • Yes, probably
  • Probably not
  • Not at all
  • Not sure

Elmhurst's response

We imagine this has been suggested from PHPP which allows for such tinkering. We think this could be of use and could work as long as any report that is needed for building regulations would be disabled if defaults are overwritten.

As before the use of occupancy already exists and this section of the SAP methodology needs to be kept up to date and work for both RdSAP and SAP in the future.

 11. Location

The large majority of SAP / RdSAP calculations (i.e. Building Regulations compliance, SAP rating and Environmental Impact Rating for EPCs) are currently done assuming the same location (East Pennines), not the actual location of the dwelling. The only exceptions are for the evaluation of PV and wind turbine contributions, for the Appendix P overheating test, and for the energy use and costs indicated on EPCs (not the ratings themselves).

Please indicate your level of agreement with the following statement:

The assessment of dwellings should be based on their actual location, not normalised as it is now.

  • Strongly agree
  • Agree
  • Neither agree nor disagree
  • Disagree
  • Strongly disagree
  • Not sure

In particular, we are interested in whether, if you think location should be taken into account, the regional zones and climatic data currently used for the overheating test (Appendix U) would be appropriate. Comments on other points are welcome too.

Elmhurst's response: 

Whilst in practice this seems sensible, this could result in some dwellings being more difficult to comply with regulations in certain areas of the country. This could result in unintended consequences and even result in developers favouring areas of the country where compliance is easier. Building regulations should be of the same level of difficulty regardless of where in the country you are.

We do however recognise that the homes being assessed can be calculated using local weather information.

SAP and RdSAP can calculate any option of the above, so this is done to policy and requirements from end users.

12. Carbon factors

Please indicate your preferred option, out of the following:

  • The carbon factors should be based on a short-term average (3-5 years) i.e. similar to the current approach in SAP
  • The carbon factors should be based on a medium-term average (20-30 years)
  • The carbon factors should be based on a long-term average (50 years)
  • Not sure

Additional comments, justification or supporting evidence

Elmhurst's response: 

We would advocate carbon, cost and primary energy factors should be updated as regularly as possible to ensure appropriate metrics are current. We would advocate that they use the latest figures certainly over the next 3 years seems sensible. Anything longer seems like gambling on technologies and innovations.

Also as we would advocate that energy assessments should only be valid for 3 years, this would solve any long term issues relating to a changing mix in energy.

 13. Modelling approach

Please indicate your preferred option, out of the following:

  • SAP should remain purely a steady-state monthly energy modelling tool, as currently
  • SAP should remain a steady-state monthly energy modelling tool in the main, but with the ability to model specific aspects more accurately (e.g. peak demand, thermal storage), using a steady state hourly step calculation (e.g. applied to shorter periods, such as a typical peak day)
  • SAP should remain a steady-state monthly energy modelling tool in the main, but with the ability to model specific aspects more accurately (e.g. peak demand, thermal storage), using a dynamic modelling calculation
  • SAP should become a fully dynamic calculation
  • Not sure

Additional comments, justification or supporting evidence

Elmhurst's response: 

No strong opinion

14. Overheating

Please indicate your preferred option for overheating tests for new dwellings out of the following:

  • There should be an overheating test, which would remain more or less as currently in the draft SAP 10 (possibly with small modifications); this could possibly feed back into the energy consumption calculation.
  • There should be an overheating test, but it should be much simpler, and flag up whether a more detailed assessment is required
  • All new dwellings should undergo a much more detailed overheating test, for example dynamic modelling against CIBSE TM59. This may mean it becomes separate from the SAP calculation.
  • Not sure

Additional comments, justification or supporting evidence

Elmhurst's response: 

Possibly a question for building regulations especially with the consultation coming on this. We would however suggest that as overheating is a very complex area that SAP is used to flag if a home is likely to overheat based on a risk assessment e.g. a traffic light system. Thus if a home was in the north of Scotland, was not in a city, was detached and had cross ventilation then it was unlikely to overheat, whereby a mid-floor flat in the centre of London, with no cross ventilation was likely to overheat, and would flag the requirement to undertake a more detailed analysis somewhere out of SAP.

15. Unregulated energy

Unregulated energy uses (e.g. appliances, equipment) contribute to total energy consumption i.e. that experienced by consumers.

Please indicate your level of agreement with the following statement:

SAP needs to better estimate all energy uses, including cooking and appliances, even if these uses do not become regulated by the Building Regulations.

  • Strongly agree
  • Agree
  • Neither agree nor disagree
  • Disagree
  • Strongly disagree
  • Not sure

Additional comments, justification or supporting evidence.

In particular, we are interested in views on adjustments that could or should be done to the current estimate of unregulated loads, measured in-use data on these loads, and how they relate to space heating and total energy consumption. Comments on other points are welcome too.

Elmhurst's response: 

We would advocate that where evidence shows that SAP is not calculating something correctly, SAP should be improved to match current understanding.

We would however state that SAP is currently very well defined as heating, ventilation, hot water and lighting. If the extra ‘unregulated’ energy is required we would see this sitting nicely in the occupancy piece, allow owners to put in what the occupants are currently using. This would sit nicely in retrofit, but not sure asking house builders to guess or default the amount of portable electronic devices in any new home would be a wise move.

16. Demand management (including demand reduction)

Please indicate your level of agreement with the following statement:

SAP needs to encourage and reward demand management (including demand reduction).

  • Strongly agree
  • Agree
  • Neither agree nor disagree
  • Disagree
  • Strongly disagree
  • Not sure

Additional comments, justification or supporting evidence

Elmhurst's response: 

See below

17. How can SAP better model and encourage demand management?

Please indicate your level of agreement with the following options. Feel free to comment on these

options or provide additional suggestions in the comments box.

 

Strongly agree

Agree

Neither agree/disagree

Disagree

Strongly disagree

Evaluate and report on peak electrical demand (kW)

 

X

 

 

 

Better account for and reward electric storage

 

X

 

 

 

Better account for and reward thermal storage

 

X

 

 

 

Better account for and reward smart technologies (other than storage) e.g. smart controls

 

X

 

 

 

 

Additional comments, justification or supporting evidence

Elmhurst's response: 

SAP and RdSAP should always be as accurate as possible using empirical data that shows that the numbers and calculations being used are proven. We welcome any improvements that make the overall calculation more accurate.

18. Thermal bridges

Please indicate your level of agreement with the following statement:

The assessment of thermal bridges needs to be improved.

  • Strongly agree
  • Agree
  • Neither agree nor disagree
  • Disagree
  • Strongly disagree
  • Not sure

Some of the options potentially available to make the assessment of thermal bridges more detailed include: requiring accurate length measurement of thermal bridges; default values which are more penalising to encourage the use of specific Psi values; a more extensive database of thermal bridging calculations for construction details.

Please let us know if you have any comments on these options, or additional suggestions and supporting information.

Elmhurst's response: 

We're not sure why this question is being asked as SAP already requires the accurate measurement of thermal bridges, and the default values are being made more onerous in SAP 10 anyway. It would be extremely rare for a new build to comply using defaults.

A database of junctions is something BRE have mentioned before, and we would support this.

19. Heat pumps

Please indicate your level of agreement with the following statement:

SAP needs to model heat pumps more accurately

  • Strongly agree
  • Agree
  • Neither agree nor disagree
  • Disagree
  • Strongly disagree
  • Not sure

Some of the options potentially available to make the modelling of heat pumps more accurate include: better taking account of heat source temperature and its seasonal variations; taking account of flow temperature and its impact on Seasonal Coefficient of Performance (SCOP); better accounting for operating profiles, to encourage designs that limit peaky on/off operation, and to take account of its effects on performance if it is likely to happen; allowing “free input” of SCOPs to represent specific products. Please let us know if you have any comments on these options, or additional suggestions and supporting information.

Elmhurst's response: 

We would advocate that where evidence shows that SAP is not calculating something correctly, SAP should be improved to match current understanding.

20. PVs

Please indicate your level of agreement with the following statement:

SAP needs to model solar photovoltaic (PV) electricity generation more accurately

  • Strongly agree
  • Agree
  • Neither agree nor disagree
  • Disagree
  • Strongly disagree
  • Not sure

Some of the options potentially available to make the modelling of PVs more accurate include: taking account of module level power electronics e.g. microinverters or DC optimisers; taking account of bifacial modules; taking account of solar module power output warranties. Please let us know if you have any comments on these options, or additional suggestions and supporting information.

Elmhurst's response: 

We would advocate that where evidence shows that SAP is not calculating something correctly, SAP should be improved to match current understanding.

21. Heat networks

Please indicate your level of agreement with the following statement:

SAP should be more accurate in how it takes account of heat networks

  • Strongly agree
  • Agree
  • Neither agree nor disagree
  • Disagree
  • Strongly disagree
  • Not sure

Additional comments, justification or supporting evidence. In particular, we are interested in views on how distribution losses should be assessed (e.g. as absolute losses, or as a proportion of demand as is the case currently). Comments on other points are welcome too.

Elmhurst's response: 

We would advocate that where evidence shows that SAP is not calculating something correctly, SAP should be improved to match current understanding.

22. Ventilation

Please indicate your preferred option, out of the following:

  • SAP should keep the way ventilation is modelled
  • SAP should broadly keep the way ventilation is modelled, but change some of the details and/or options available – please detail in the comment box
  • SAP should fundamentally change the way ventilation is modelled – please detail in the comment box
  • Not sure

Some of the options potentially available to modify the modelling of ventilation include: entering the length of duct runs; further encourage the use of rigid ductwork; introduce a penalty on ventilation performance in as-built calculations, until evidence of commissioning is provided; introduce improvements to the parameters provided in Appendix Q / PCDB e.g. taking account of filters in Specific Fan Power values. Please let us know if you have any comments on these options, or additional suggestions and supporting information.

Elmhurst's response: 

There certainly could be more inputs such as suggested above to improve the accuracy of ventilation modelling. Also a penalty for non-commissioned systems seems sensible.

 23. Hot water

Do you have evidence of how actual hot water consumption in-use compares to that evaluated in SAP? This could be in kWh energy for hot water or in litres of hot water (per person, or per sqm).

Elmhurst's response: 

No evidence

24. Refrigerant leakage

Currently SAP does not account for greenhouse gas emissions from refrigerant leakage (e.g. heat pumps).

Please select your preferred option(s) out of the following (you may choose several):

  • Refrigerant leakage is an important issue, but it should be dealt with in another way, outside of SAP
  • Emissions associated with refrigerant leakage are not part of ‘operational carbon emissions’: they are part of embodied global warming potential emissions, so they should not be included in SAP
  • Emissions associated with refrigerant leakage should be an output from SAP, as indicator or as a separate metric
  • Not sure

Additional comments or suggestions:

Elmhurst's response: 

We would support the second option as they are not part of the ‘asset’.

25. Performance gap

Please indicate your level of agreement with the following statement:

SAP /RdSAP should play a bigger role in reducing the performance gap.

  • Strongly agree
  • Agree
  • Neither agree nor disagree
  • Disagree
  • Strongly disagree
  • Not sure

Additional comments or suggestions: 

Elmhurst's response: 

There are areas where SAP contributes to the gap such as use of defaults, standard occupancy and usage patterns etc. I believe SAP could be reviewed to look at areas that contribute to the gap. The key to understanding this question is that the models are known, there are of course improvements to be made as we have advocated above in some of our answers.

Most of the performance gap lies in the quality of what ends up being built in the field. The current compliance of paper is known. When the build deviates from the design, the performance gap starts to deviate, when substitutions are made to technology and products the performance gap widens. This is why we have advocated in the current regulations to improve the at design stage checks to ensure compliance. We also advocate then to model for the occupants, so that a prediction of energy can be predicted, then finally use the metered data to check for successes or failures. This way if the home uses (within a reasonable tolerance) the predicted amount of energy then there is no issue. If it doesn’t then it is worthy of investigation, was it the asset calculation, or was it the operational use by the family, was it a particularly cold winter for example can be analysed by experts to give the right answer.

Using a closed loop process then to identify whether the asset calculation, the occupancy model or anything else needs to be amended to be more accurate, would then drive continuous improvement.

So we need to understand the asset (use SAP), understand the occupants (occupancy) and finally measure in use energy (meter). One without the other means we wouldn’t know where the issue lays. If we build upon the current infrastructure but vitally add occupancy and meter then we can manage all the homes in the UK.

26. Options for SAP / RdSAP to help reduce the performance gap

Several options are potentially available to modify SAP/RdSAP and help reduce the performance gap. Some of these options are covered in earlier questions of this survey.

Please indicate your level of agreement with the following additional options. Feel free to comment or provide additional suggestions in the comments box

 

 

Strongly agree

Agree

Neither agree/disagree

Disagree

Strongly disagree

Improving accessibility and transparency e.g. opensource calculations, easily available evidence base

X

 

 

 

 

Including a measurable space heating metric (e.g. Heat Transfer Coefficient) on the SAP output report and EPC report, to make direct comparisons with as-built values easier

X

 

 

 

 

Introducing a penalty on asbuilt system performance unless there is evidence of commissioning results

X

 

 

 

 

Improving the information set-out in SAP output reports and EPC reports for home occupiers

X

 

 

 

 

 

Additional comments, justification or supporting evidence.

Elmhurst's response: 

Strongly agree with all these above as per previous answer


Article published: 11/12/2020

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