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The EPC Dilemma: How Current Ratings Fail Heat Pumps

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(@chris-flaherty)
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This article isn’t meant to criticise heat pumps; rather, it questions the effectiveness of the EPC system for energy ratings. In December 2023, I completed a comprehensive refurbishment of a flat, enhancing its layout and adding internal wall insulation (IWI) to all external solid walls, substantial loft insulation, underfloor insulation, and new double glazing. The plumbing overhaul included a new bathroom and kitchen. For the heating, I recommended an air source heat pump (ASHP) and underfloor heating (UFH) to the client, who was receptive to my advice given the system's energy efficiency.



I installed a Vaillant UK aroTHERM plus with a Joule Heat Pump cylinder. The UFH system was designed by the manufacturer, tailored to the heat loss calculations of each room. For control, I chose Vaillant’s sensoCOMFORT and weather compensation control. Considering the compact size of the flat, I didn't install a buffer tank; the only pump used was the one integrated into the aroTHERM ASHP. I deemed individual room temperature control unnecessary for such a space and opted for a full weather-compensated control for the entire property. The system was well insulated both internally and externally, performed well, and heated the flat effectively with a flow temperature capped at 45C.

When it came time to obtain an Energy Performance Certificate (EPC), I encountered the system's shortcomings. Despite the extensive upgrades, the walls, windows and roof received good ratings, but the ASHP and UFH were only deemed 'Average'. Moreover, the hot water system was rated 'Poor', and the weather compensated control was rated 'Average', possibly because it was categorised as a programmable room stat rather than a weather compensated control. This raises the question: What system would achieve a 'Good' or 'Very Good' rating if not an ASHP with UFH?

The EPC rating is a significant factor in convincing homeowners to switch to heat pumps. Is this an issue with individual assessors, or is it the SAP calculations they must follow? In my view, the current EPC system is outdated and potentially detrimental to the heat pump industry. I’m curious to hear others' experiences with EPC ratings and their thoughts on its impact on the adoption of heat pumps.

Editor's note

The EPC is a vital tool for homeowners, offering a detailed overview of a property's energy efficiency and carbon emissions. This rating is not only crucial for understanding a home's energy performance but also influences property values and compliance with environmental standards.

However, as Chris points out through his firsthand experience, there appears to be a discrepancy in how EPCs evaluate certain energy-efficient technologies. The case in question involves a comprehensive refurbishment of a flat, where various energy-saving measures were implemented, including the installation of an ASHP. Despite these sensible upgrades, the EPC assessment yielded unexpectedly average ratings for the ASHP and underfloor heating, and even a poor rating for the hot water system.

This raises important questions about the current EPC system's ability to accurately reflect the efficiency and environmental benefits of ASHPs. Are these innovative heating systems being unfairly penalised by an outdated assessment methodology? If so, this could inadvertently discourage homeowners from adopting ASHPs, which are known for their energy efficiency and lower carbon footprint compared to traditional heating systems.

Going forward, the SAP calculations must be revised to better account for the specific efficiency and performance characteristics of air source heat pumps, considering factors like weather compensation control, underfloor heating integration and system sizing.


   
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(@Philip Taylor)
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I believe most EPCs are done quickly and cheaply by people with minimal training and probably very limited understanding of heat pumps.Maybe the ASHP manufacturers or installers could provide a list of EPC certifiers who know the subject. Might be a bit more expensive but would give the correct rating.


   
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Toodles
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More proof (if proof were needed!) that EPC’s aren’t necessarily equal or valid. The referenced presentation is about some Passive Houses that only rate a ‘B’ EPC!!!

Regards, Toodles.

Toodles, 76 years young and hoping to see 100 and make some ROI on my renewable energy investment!


   
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Abernyte
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As I understand the system, SAP (and by default RdSAP) is a CO2 reduction assessment/tool so if the house is not a new build then the EPC reports are done using the RdSAP method, which is based on the age of the house and the price of its primary fuel source, not how well it is constructed, so could give confusingly low score for a passive house.  I did not watch the video so I am not sure if this was a new build or not.


   
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(@heat-pump-newbie)
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I had a "whole house survey" done as part of the BEIS EoH trial, which included an EPC rating.

My bungalow (which had a G rated ie inefficient gas powered heating system) was rated 53 E.

After the heat pump was installed it was re-evaluated and it scored 71 C. However, the hot water is considered Poor 'from main system' - that's quite ridiculous as I get a COP of around 2.5 even in winter. 

Also the Main heating control is rated Average with the suggestion for improvement to install Zone controls, which as we read everywhere makes heat pumps less efficient !!!

The EPC system definitely needs work.

Screenshot 2024 02 24 at 11.44.59

   
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(@kenbone)
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Just had my own EPC done recent, heating deemed as poor, I have a heat pump, Battery's and PV.

EPC system is not fit for purpose. 

This post was modified 2 months ago by Mars

Technical Manager & Professional Installer: Ultimate Renewables


   
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Toodles
(@toodles)
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@abernyte A ‘Housing Association’ type New Build. Toodles

Toodles, 76 years young and hoping to see 100 and make some ROI on my renewable energy investment!


   
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(@ajn9000)
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This is a known problem and IMO is taking far too long to sort out.  The problem exists right at the top of the tree with the UK standard/methodology (SAP / RdSAP) - which is then used as the base specification for EPC software etc used by the industry.  So the 'error' is hard wired into the entire system.  The best informed reference I have found about this:

I am a retired Head of Medical Physics (NHS) and have been working on project to support parish residents to improve the energy efficiency of their homes (retrofitting).  We crashed straight into this and our practical 'sticking plaster' was to add some wording about this into retrofit survey reports to alert homeowners about the shortfalls in the modelling.  This is particularly a problem with multiple renewables, eg, ASHP + solar PV + battery.

RdSAP V10 should have been released this month, but has now been delayed until 'summer'.  I am told by those who know that V10 will improve the situation.             

There needs to be a much stronger lobby on this.  If anyone is inclined to write to their MP - this would be a good topic!


   
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Toodles
(@toodles)
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@ajn9000 Very interesting - and somewhat of an eye-opener as to how inadequate the EPC regime is! After reading this and being curious, I studied my own EPC which only made recommendations for solar heating for the DHW and fitting some PV panels. No mention of heat pump at all. To be fair, the EPC included a link to follow if I wished to carry out further improvements; on that site, I found the link to the BUS scheme. I feel this is rather a second-hand way of providing further reading and is hardly ‘in your face’, it is as though the powers that be don’t believe in or want anyone to even consider heat pumps!!! Harrumph, Toodles.

 

 

Toodles, 76 years young and hoping to see 100 and make some ROI on my renewable energy investment!


   
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(@ajn9000)
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@toodles your EPC is a limited tool that needs to be affordable to produce - hence it heavily relies on modelling.  It is geared to produce a rating, rather than an improvement plan.  A retrofit assessment (as per PAS2035: https://www.trustmark.org.uk/business/information-guidance/pas-20352019-pas-203020352023) is much more useful to households, but still uses RdSAP methodology.  Best to view this and EPCs as art, not science.

With what I now know, I believe that there are thousands of households holding EPC certificates who may well have been encouraged to be curious about heat pumps if the SAP / RdSAP methodology had been more fit for purpose.

Lots going on behind the scenes, eg see attached from Elmhurst.  But also lots of missed opportunities, past and present.  

          


   
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