In support of EPCs
Last month, MBS raised the issue that some building performance specialists view EPCs as ‘not fit for purpose’. Here Dr Andrew Geens makes the case for EPCs as an energy efficiency measurement and clarifies his position on why EPCs are a useful indicator for building owners and managers.
The April 2018 issue of MBS included an article reporting on Dr Robert Cohen’s presentation at ECObuild earlier this year (See here).
In the article I was correctly quoted as saying “It is very important to bear in mind that the EPC is not a prediction of running costs or long-term performance”. The interesting thing is, that the April article was making the case that “EPCs don’t make the grade for true energy measurement”, whereas my original comment was part of a discussion where I was making the case in favour of using EPCs as an energy efficiency measurement.
So this article sets out to make this clear, just in case anyone reading the April item thinks I was agreeing with the thrust of the article, rather than offering an alternative view. To be fair to the editor, it could have been read either way.
EPCs are used to satisfy a legal requirement for energy information for incoming occupants on construction, rental or sale. The nearest familiar equivalent is mpg for a car, designed to help you decide which car you want, not to prediction the actual fuel performance.
Criticism is being levelled at EPCs on the basis that they do not predict actual energy consumption. For their primary purpose, this criticism is correct in that, to make an informed decision on which building has the best potential to give you good energy performance/lowest energy consumption, a standard occupancy pattern is universally applied, so self-evidently this is not a prediction of what will happen when actually occupied.
The better alternative for predicting energy consumption would be something like CIBSE’s TM54, “Evaluating Operational Energy Performance of Buildings at the Design Stage”, but this still relies on estimates and assumptions and is only considering the building at design. The majority of EPCs are produced for existing buildings, so this also needs to be acknowledged in any criticism.
Of course, what everyone is ignoring when criticising the EPC is that whatever modelling you do at the point of occupancy, that model will be based on assumptions, as the building is not actually occupied yet. For a new build, there has never been an occupant, and for rental and sale purposes, the previous occupants’ use of the building, and the effectiveness of their energy management systems are not a reliable indicator of how the new occupants will use and manage the building.
Even if the potential occupier can provide a detailed specification for their expected occupancy, it is still likely to change when someone walks through the door. Longer or shorter hours, more or less people, different business activity - the permutations are endless. Furthermore, to satisfy the regulatory requirement there would need to be universal agreement on any modelling assumptions, and it would also need to be affordable for the corner shop or doctor’s surgery.
So for clarity, EPCs are not designed to predict actual energy performance, they provide a simple indication of the asset rating. However, I may have been understating the usefulness of EPCs when I was pointing out that they are not designed to predict the actual energy consumption of the building. When I am asked what organisations should do to reduce their energy bill, usually in the context of improving their Display Energy Certificate (Operational) rating, there are two types of action they can take. Firstly they can adopt new or better energy management techniques, and secondly improve the inherent energy performance of their asset.
What could they do to improve the asset?
• Replacing an older boiler would help to reduce energy consumption, but would it improve the EPC rating? Yes it would
• Improving the average fabric u-values would help to reduce energy consumption, but would it improve the EPC rating? Yes it would
• Improving the lighting efficacy would help to reduce energy consumption, but would it improve the EPC rating? Yes it would
• Replacing an older hot water system would help to reduce energy consumption, but would it improve the EPC rating? Yes it would
• Improving the building air tightness would help to reduce energy consumption, but would it improve the EPC rating? Yes it would
• Controlling solar gains would help to reduce energy consumption in an air conditioned building, but would it improve the EPC rating? Yes it would
• Installing photovoltaics will help to reduce the metered electricity consumption, but would it improve the EPC rating? Yes it would.
The EPC does not take account of a lot of other energy use; lifts, small power and catering equipment for example, but this will be broadly the same whichever building is occupied by a particular company, so this won’t need to be accounted for in building selection and is reasonably straightforward to factor in for predicting actual running costs. The important thing is to be aware of what the EPC is doing and what it is not.
In conclusion, although not primarily designed as a tool to predict energy consumption in the detailed kWhr/m2 to 2 decimal places sense, an EPC provides an incoming occupant with a strong indication of whether their energy consumption will be high or low in relation to other buildings being considered, and without spending a lot of money on detailed modelling which still involves a lot of assumptions, this is good enough for most situations where property is changing hands.
Dr Andrew Geens is head of CIBSE Certification