At least one WA home a week is set alight by a roof space fire, prompting warnings to homeowners to ensure insulation is properly installed.

The rise in roof space fires has highlighted a serious hazard in homes and Consumer Protection Commissioner Anne Driscoll said she feared more homes were at risk due to the Federal Government's energy efficiency subsidies, which has boosted insulation installations.

"This increase in demand for roof insulation due to the subsidy may attract inexperienced installers to the industry and there is a danger if the product is not being installed according to our strict safety guidelines," Ms Driscoll said.

"We are finding, in some cases, the insulation is too close to electric cables, ceiling fans, down lights and their transformers, creating a serious fire danger in the home.

"Although most ceiling insulation is fire resistant to some extent, there is still a possibility of ignition if the insulation covers these electrical devices in the roof space or is exposed to the heat generated by them."

Fire and Emergency Services Authority fire investigation officer John Haddon said roof space fires were often undetected as smoke occurred above smoke alarms.

"Often people only know their house is on fire when flaming material comes through air conditioning vents or the ceiling collapses," Mr Haddon said

Home owners should ensure there is a 50mm clearance around incandescent lamps and a 200mm clearance around halogen lamps. All installations should comply with Wiring Rules (AS/NZS 3000) -2007.

Down light guards should also be fitted before insulation is put in.

Blow-in (or loose-fill) insulation, which is sprayed with an adhesive solution to prevent movement, can move around the roof space if not secured properly.

Blades of an exhaust fan can get jammed, causing it to overheat.

Consumers are also urged to buy insulation which has a higher fire resistant rating.

"There is no concern if the insulation is installed correctly and in accordance with these safety standards and all installers and electrical contractors should be aware of, and abide by, this extremely important requirement to ensure maximum safety in the home," Ms Driscoll said.

PERTH LISA CALAUTTI