The problem with older recessed downlights, one expert says, is that each one is literally a hole in the ceiling, letting all the heat escape.

Dr Nelson Lebo, Eco Design Advisor for the Palmerston North City Council, said older ceilings with downlights were like a block of Swiss cheese.

Older downlights used halogen or filament-type bulbs that could get so hot that the insulation in the ceiling would catch fire if allowed to touch them. So holes were cut in the insulation around the downlights and that's what causes the problem, Lebo said.

"In winter any heat that is generating through the home is going up through those holes. And in summer, heat build-up in the ceiling cavity can radiate down through the holes. It's a lose-lose situation," he said.

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Naturally Lebo had a solution. It was not free and required an electrician but it would save you cold hard cash on your power bill in the first year of installation.

"What you need to do is swap out your old downlights with LEDs which are IC rated to be abutted and covered with insulation.

"If you've got downlights and a cold home, this is the first and best thing you can possibly do," Lebo said.

"And once the LEDs are in, top up the entire ceiling with another layer of insulation."

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