Industry concerns have been raised after more than 1000 compliance flaws were discovered in a government energy efficiency audit covering only a small fraction of building approvals.
Between July 2016 and June 2017 the government randomly audited 616 separate energy efficiency ratings, discovering a combined total of 1264 non-compliances.
The rating system is used to show a building's energy efficiency when it is either first built, or when it is sold or leased to a new owner.
Common issues discovered during the audit process included failures to submit required documents, failures to correctly model a building's air leakage, and the use of the wrong window sizes to calculate ratings.
Industry figures have been quick to criticise the ACT government's audit process and the administration of the energy efficiency scheme in general.
Trevor Lee, a director of Canberra's Exemplary Energy Partners consultancy, said the use of out-of-date software was affecting the reliability of the energy rating scheme.
"For six years or so the software that has been used to rate existing houses is different from the software used to rate new houses, which is much closer to simulating reality," he said.
"The bureaucracy is still reluctant to have the ratings done with the same software, so that a rating of a house when it is built is the same as the rating given during the building approval process."
Stronger enforcement action was also needed to weed-out businesses operating in the sector without the right skills or experience, Mr Lee said.
"You've got this result of rampant non-compliance, but who has lost their licence," he said.
"It should be three strikes and you're out for 12 months."
Of the 616 audits performed by the ACT government, 222 covered new residential building approvals and 384 covered old buildings that were being sold or leased.
The number of audits performed covers about 5 per cent of the relevant energy ratings awarded.
The vast majority of these were desktop audits, with just 10 physical inspections performed during the audit process.
One Canberra energy rating professional, who asked not to be named, also raised concerns about the software used to devise ratings, as well as the desktop audit process.
"They did their audit from their desks. You cannot do an energy rating audit from your desk, you have to go on site," the professional said.
"There are also massive issues around the lack of training. Practically anyone can go and have a crack at this if they can muddle their way through the software," they added.
An Access Canberra spokesman said the government was confident in the effectiveness of its residential energy rating audit process.
"Through its compliance framework, Access Canberra has been actively working with the EER industry to improve the quality of rating documentation and to reduce the number of non-conformances occurring," the spokesman said.
The government would perform physical audits on a further six buildings this financial year, the spokesman added.