The body that represents assessors who perform the testing of energy performance has challenged some of the findings in a report led by Atom Bank on the real scale of CO2 emissions.
Released today, the study by Atom in conjunction with Experian and the University of Durham and British banks could estimate the CO2 emissions of houses in their mortgage books by no less than 50%.
It suggested that this was due to their dependence on EPC assumptions to calculate emissions, instead of meter lectures.
The research also showed that there was no significant difference in emissions between houses with the best and worst EPC reviews.
But The Property Energy Professionals Association, which represents the energy rating agents who give houses their EPC reviews, has warned to throw the schedule.
It has also pointed to the disadvantages of the focus of the study on metarm measurements as an alternative way to measure emissions.
Pepa chairman Andrew Parkin says: “EPCs are based on standardized assumptions and use carbon intensity data available at the time of assessment.
“As the energy mix of the VK evolves – especially with the carbon atoms of electricity – the carbon factors used in EPC calculations may become outdated.
“The EPC reform consultation is investigating whether we should reduce the 10-year validity period of EPCs and this research suggests that they should be considerably reduced.”
Pepa is supported to reduce it to three or five years.
Parkin also points out that the occupancy rate and the behavior of homeowners are not recorded in EPCs.
He says: “It is crucial to acknowledge that EPCs do not actually measure energy consumption.
“They estimate the energy needed to maintain a reasonable level of comfort in a home, based on standard occupation and user patterns.
“Comparing EPC estimates with actual meter lectures combines two fundamentally different statistics.
“In fact, use is influenced by behavior of occupants, affordability and lifestyle choices – none of which EPCs are designed to catch.”
Parkin says that the observation that houses can use comparable amounts of energy over EPC tires A to G, “is intriguing but must be interpreted with caution”.
Financial restrictions can mean that they use less energy in lower properties, in particular those housing families in fuel poverty.
He says: “These households can heat their houses, which leads to lower actual consumption, but a poorer health and welfare results.
“EPCs estimate which energy needs to be used to achieve comfort – not what is actually spent.”
Parkin argues that policy makers and stakeholders are not only allowed to focus on the actual energy consumption in the drive to Net Zero.
He says: “EPCs play a crucial role in identifying where improvements can be made to reduce the demand for energy and to improve building performance.”