You may be using your fan the wrong way, says eco expert

Not a fan of the hot nights. Hannah Ouellet prefers to sleep with the windows open. Photo / John Borren

If you've been wondering why you've been suddenly sleepless, ask the experts.

Overnight temperatures have been 3.2C hotter than normal in the first two weeks of February forcing many people to resort to fans or air conditioning to help them sleep at night.

But, if you're still feeling the heat, Eco Design adviser Nelson Lebo says it might be because you're using your fan ineffectively.

It might sound counter-intuitive but pointing a fan outside a window was far more effective than having it blowing in a room, according to Mr Lebo.

"It's physics," he said. "You want to blow hot air out and have cold air coming in.

"Even if there's warm air in the house, when air is moving, it feels cool on our bodies."

Mr Lebo, an American living in Whanganui, said he first caught on to the idea from his grandma who would put her fan facing out the window during mid-30C days in Detroit.

"When the outside temperature drops below the inside temperature; you really reap the benefits."

The "chilly bin" method was another alternative, he said.

"This is actually more effective. The idea is to make your house like a chilly bin.

"Keep your windows, curtains and doors closed during the day so cool air from the night before remains inside and hot air from the day can't get in."

NIWA forecaster Chris Brandolino said the minimum daily temperature, which was typically overnight temperature, for the first 13 days of February was 18.7C - 3.2C above average.

"That's well, well above normal," he said. "The water temperature is well over 20C so when you have the air coming off the water it will keep you warmer at night."

The mean maximum air temperature over the first 12 days of the month was 24.7C, 0.7C above average, he said.

Mr Brandolino said weather maps from the last two weeks showed there had been lower pressure than normal and winds from the north and northeast.

He said the Bay of Plenty region usually had a fair amount of wind which came from the easterly direction which would have been pushing up temperatures.

"Because of that it's going to keep you warmer at night. It's coming off water that's 21C, 22C or 23C. It's going to keep you warm and humid, especially northeasterlies."

In the first 12 days of February, 43mm of rain had fallen.

"It's about spot on in terms relative to the month. That's 49per cent of normal. In a typical February month you'd get 86mm of rain."

In January the average minimum temperature was 17C which is 1.9C above average.

Mr Brandolino said the forecast for the northern part of the North Island, which included the Bay of Plenty, was for temperatures to be above average for February, March and April.

There was an equal chance of rainfall being near normal or below normal, he said.

Tauranga resident Hannah Ouellet said she had been struggling to get a solid night's sleep because of the heat. "You definitely wake up a few more times at night than you usually do. You have to have a fan or open the windows."

The 18-year-old said she usually opted for an open window "and then have one leg awkwardly sticking out".

"My dad has never had to use a fan to sleep before but he's got one out this year."

Aircon Tauranga sales manager Andrew Stockman agreed the heat, especially in bedrooms, had been "unbearable".

"Sleep is not as good as it should be and people have been tired and grumpy."

He said demand for air conditioning units was well above normal this year.

The company had already sold about 50 units for existing houses since mid-January, slightly more than double the amount sold in the same time last year.

"I've been pretty much just on the go all the time," he said. "It's warmer than normal and muggier as well."

Mr Stockman said it may be because the heat had lasted longer than usual so people had decided to do something about it.

Smart Sparx Electrical director Hayden Barnsdall agreed his company had also been a lot busier this summer.

Tips for keeping your house cool

• Try to create a cross draft by opening windows throughout the house. Closing curtains will also keep the sun out.
• Ceiling and floor standing fans are relatively cheap to buy and install, and are cheaper to run than air conditioning.
• Think about planting deciduous trees on the north and west of the house to provide shade in summer. If you don't have trees, eves or roof overhangs stop sun entering the house.
• Try using the fan-only setting on air conditioners which can help create cross-draughts in your home.
• Use the dehumidifying mode - if it's the humidity rather than the temperature that's the problem. Shut your doors and windows in the rooms you're dehumidifying.

Energy Efficiency and Conservation Authority