The Association, whose members let more than a third of residential properties in rural areas, said a new consultation on the way older properties are assessed would help to highlight the flaws in the current system.
CLA President Harry Cotterell said:"The CLA has long argued that EPC assessment for older properties is flawed. The software used has been designed for modern properties and does not take into account elements such as wall thickness within older properties. EPC ratings results are artificially low because of this.
"This has ramifications for CLA members because by 2018 let residential property is required to have an energy efficiency rating of 'E', and anything below that will not be appropriate for letting."
Mr Cotterell added: "It is important DECC takes into account recommendations made by the Sustainable Traditional Buildings Alliance. This will help Green Deal assessors make meaningful calculations on the types of energy saving interventions most appropriate to older properties. "We do not want to see housing supply reduced in rural areas because properties are not deemed lettable due to faulty assessment procedures."