Do Energy Performance Certificates actually perform when it comes to a renovation?

The accredited EPC assessor arrived with a clipboard. Was that, I enquired, all he needed?

Perhaps it was my imagination but he seemed mildly affronted. He assured me he was fine, and repeated himself when I offered to show him round and answer any questions since it was my self build he was assessing.

I gained the distinct impression that I was ever so slightly annoying him, so I made my excuses and left. After all, this was only a legal formality, required because I had just become a landlord. Of a one-bed garden flat, newly converted from an existing ground floor.

Originally this housed an integral garage, an en suite bedroom and a self-contained patio. But it fast became a dumping ground, so my wife and I decided to turn it into a rental, in the mildly desperate hope of reducing our horrendous mortgage repayments. And so, via our rental agent, we were introduced to Energy Performance Certificates (EPCs).

These rate properties from A to G, based on the estimated costs of heating, lighting and hot water. Valid for 10 years, they’re intended to give prospective owners, or tenants, an idea of likely energy bills, alongside the potential costs and benefits of investing in energy-saving measures.

Since April 2018 rental properties have needed a minimum EPC rating of E, which, happily, was the rating achieved by our flat.

The four-page EPC report also suggested that the flat’s energy efficiency could be improved dramatically by insulating the cavity walls and the suspended floor, fitting high heat retention storage heaters, a heat recovery system for the shower and high performance external doors. We might also consider external wall insulation, a biomass boiler or a heat pump. All this could save us £1,275 over three years - by only spending an estimated £3,700 to £5,700 (presumably not including the £8,000+ heat pump).

To which my reaction was: what? As I could have told the assessor, the flat was part of a timber-frame building with 100mm of mineral wool in all the walls. A similar depth of rigid polyurethane insulated the ground floor and the flat’s external doors were high-performance Swedish models.

To be fair, EPC ratings can be officially complained about, but, frankly, given the threadbare nature of the exercise there didn’t seem much point.

Today, however, the government makes EPCs a central part of its decarbonisation programme for UK homes. The current target is to bring as many as possible into band C by 2035. Around 16 million in England alone - roughly twothirds - are now rated D or worse.

So how practical a guide are EPCs to a would-be renovator, especially one keen on an eco-retrofit?

Neil Hargreaves, MD of Knauf Insulation, describes them as a ‘tickbox exercise’ because they are based on modelled performances rather than actual measurements. He told the BBC earlier this year: “Our data suggests this performance gap is often as much as 30 per cent, and we’ve found cases where it’s even higher.”

"For the individual renovator a more practical alternative is a home energy audit by a specialist company."

Knauf Insulation has developed a system which monitors energy performance through sensors, weather data and energy meter readings, all monitored by a ‘nega-watt hour’ meter, measuring energy saved rather than expended. It was recently trialled with the refurbishment of a 1970s housing estate in Trafford with EPC ratings of D or E and produced a 31 per cent average improvement in energy efficiency. But the EPCs were unable to reflect it and remained the same.

For the individual renovator a more practical alternative is a home energy audit by a specialist company. Based in London and Norwich, Enhabit (enhabit.uk.com) offers both energy surveys and fabric option assessments, using the Passive House Planning Package - currently the most accurate method of guaranteeing the energy performance of a home, whether existing or new build.

Ecofurb (ecofurb.com), another London-based firm, provides both home audits and building performance specifications for the renovation work. It can also provide quotes from vetted contractors and a co-ordinator to oversee the work and sign it off on completion.

Cosyhomes, Oxfordshire (cosyhomesoxfordshire.org) supplies a similar retrofit service. It includes home assessments, approved contractors and retrofit coordinators to manage your project.

Home energy audits, however, remain largely unknown to most homeowners, who may accept the £45 or so cost of an EPC but balk at the several hundred pounds of a much more comprehensive survey - even though the resultant energy savings should easily cover the outlay.

But perhaps a radical new retrofit service currently being developed in Scotland may change attitudes. Dundee-based IRT Surveys, an awardwinning thermal imaging and retrofit company, is best known for its DREam system for rapidly surveying buildings, using thermal imaging, drone footage and an ingenious algorithm which produces an instant and accurately costed assessment of heat loss.

To date it’s been used mainly for assessing social housing as well as public buildings. But a new software system aims for a much wider audience. Known as HEERO (Housing Energy Efficiency Retrofit Optimiser), it combines IRT’s existing system with Google Earth and WRLD, an app which provides 3D images of every building in the UK.

HEERO will be able to locate your home from the location of your mobile phone, establish its EPC, question you about its size, age, construction and worth, provide impartial advice on energy-saving measures, compare loans to finance them, alert you to appropriate grants and even connect you with a Trustmark-accredited contractor to do the work. As CEO Stewart Little says of IRT’s DREam software: “It helps roadmap the journey to net zero.”