A report for the Government's Energy Effici' />
Authorities are putting the heat on companies "overselling" the benefits of home ventilation systems.
A report for the Government's Energy Efficiency and Conservation Authority (EECA) found some manufacturers were promoting systems as a way to generate heat, despite having no evidence to back the claim.
The findings have prompted the authority to caution consumers while they attempt to establish a regulatory body.
An estimated 150,000 ventilation systems have been installed in New Zealand homes over the past eight years.
They can cost up to $4000 and Jeremy Penrice, who has more than 25 years' experience in the air-conditioning and controlling industry, said many customers were wasting money.
"Most of these systems don't actually have anything on them that controls the temperature or humidity like they say they do - it's basically just a fan," he said. "They take air from the roof and circulate it through your house, and quite often the roof can be contaminated and dirty."
Forced air-ventilation systems blow dry air into the house from roof space. They work best when the roof is dry and warm on sunny winter days.
EECA said while some manufacturers claimed the systems could recover heat from the roof, this was often impossible during bad weather.
"Some providers make claims that the heat recovered from the roof space and recycled back into the house could save up to 60 per cent in room heating costs, but there is no independent evidence to back this up," said a spokeswoman. "If people are thinking they will heat their homes, especially in winter, they could be disappointed."
Independent energy efficiency consultant Norman Smith said the industry had to "get its act together".
Smith is helping EECA to establish the New Zealand Home Ventilation Authority, to regulate providers and help consumers make an informed choice.
"The prime role of a ventilation system is to ventilate a home and remove the dampness, which makes it easier to heat.
"There could be some heat gain with these systems at some point during the year, but just how much that is no one knows.
"These claims about how much heat can be gained must be backed by legitimate research, which is what we are working towards."
Bob Batenburg, general manager of major player DVS, is part of the working group helping to set new standards.
He said his company operated on the basis that heat could be generated "when available".
"Ventilation systems have generally been sold as condensation controls, but the market has shifted and some players are heavily marketing the heating aspect of it, which has caused some confusion," he said. "Any claims that they heat your home are silly."
Marcus Foot, managing director of rival company HRV New Zealand, welcomed moves towards regulation.
"At the end of the day ventilation systems are a significant part of the solution but they are not the silver bullet. Anybody claiming that is full of rubbish.
"We are trying to mature as an industry and we're having to legitimise ourselves."