Brian Mark, director at Fulcrum Consulting and a member of the Renewables Advisory Board, made his remarks following the release of a report by the All-Party Urban Development Group.
The report, Greening UK Cities, proposed measures to improve the performance of buildings, including extending DECs to privately owned commercial buildings.
It also said a national building performance database needed to be set up to record the real energy performance of buildings – including the efficiency of heating and ventilation systems.
Mr Mark said: “There is an appalling lack of actual data not just for existing stock, but in all buildings. If you want secure policy direction about energy usage you have to start with some form of real data.”
Mr Mark said energy performance certificates were inadequate, since they were only calculations of how a building should perform.
“EPCs are based on whatever you do to get past Part L of the building regulations. Only DECs, which at the moment are only applicable to civic buildings, are based on real meter readings. Until we do this, we will be basing national policy on complete guesswork.
“There is obviously a reluctance to introduce them because when you look at meter readings you find a building is not performing anywhere near as predicted.”
Mr Mark added that existing commercial stock presented a challenge, as many renewable strategies were inappropriate on inner city commercial buildings with small footprints and higher-than-average electrical loads.
The authors of Greening UK Cities were optimistic that action could be taken if policy were better directed. The report said Government needed to streamline its approach and make a single department responsible for energy efficiency. It also argued for the raising of efficiency standards, effective enforcement and a review of incentives and grants.
Richard Hipkiss, sales and marketing director at i-prophets energy services, said: “It would be fantastic to have every building with a DEC. A database to monitor carbon emissions would also be of great value. The data gathered by the Carbon Trust at the moment is only scratching the surface. The information in a DEC is also valuable to the customer.”
Paul King, chief executive of the UK Green Building Council, said the report identified market opportunities if the Government took effective action in response.
“There is a huge potential market in retrofitting and refurbishment.
“If we can unlock this, we’ll deliver lower-carbon buildings, lower energy bills and a more productive working environment for occupants,” he said.
Tim Dwyer, head of the Department of Engineering Systems at London’s South Bank University, said that DECs could become a “badge of honour” for refurbished buildings.
He said: “It would be a great boost to building operators and occupants to see how they are managing energy use and making a difference.”