Discussing the research, director of housing at the financial company, Stephen Smith, said: "Over time buyers will be likely to implement some of the energy-saving recommendations as they make improvements to their home.
"This will result in valuable cost savings on heating and lighting bills, given the recent upward year on year trend in overall utility bills."
Mr Smith added: "Whilst no-one is going to feasibly install double-glazing into a period thatched cottage, there is room for reasonable and appropriate improvements in many properties."
The release of Legal & General's findings follow the director general of the Association of Home Information Pack Providers (AHIPP) backing Energy Saving Week to increase awareness of the EPC.
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