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Top tips for keeping your home cool during the hot spell

With today predicted to be another sweltering day around NZ, one home design expert says applying physics is the best tool to keeping your cool.

Whanganui-based Nelson Lebo says heat enters a building in three ways; by shining through windows, as hot air flowing inside doors and windows, and as heat entering walls and ceilings.

"A sheer curtain allows light to come through but not heat," Mr Lebo says.

Mr Lebo’s known as a hot house expert for his tip to remove heat from homes that went viral in New Zealand in 2016, and also due to the advice he provides to Palmerston North residents on how to cool down houses as an eco design advisor for the city’s council.

"All you need is a fan, and two windows to keep cool.

"Anyone can do it... the results speak for themselves," he told 1 NEWS.

Once the outside temperature starts dropping around 8pm, Mr Lebo said a fan should be directed outside through an open window and a window in the room you want to be kept cool should be opened.

The fan acts as an extractor, drawing in cool air and directing the hot air inside the house outside.

"Running an air conditioner is really expensive but there’s free, cool air outside overnight, running a fan is cheap so let’s use the cool air."

The cost of operating the fan is a few cents an hour, on average.

Mr Lebo said the temperature in the room will drop by three to six degrees Celsius, which can be the difference between a restless night and a sound night’s sleep.

He said some people he’s shared the tip with have been dubious, but it always works, as long as the same amount of air is able to exit and enter through similar sized openings.

An indoor-outdoor temperature can be used to determine when it’s time to start the fan.

People can try it with a bathroom extractor for a similar, but less powerful, effect, he said.

Mr Lebo said people should keep their windows and doors shut the next morning to trap the cool air inside as long as possible.

Curtains should be drawn when sun is in the opposite direction, acting as an insulator to block the heat.

"The secret is treat your house like a wind tunnel at night and a chilly bin through the day."

For those building a new home or renovating, Mr Lebo said insulation is the key to blocking heat in the summer and staying warm in the winter.

"There's no extra cost to building a house that doesn't overheat maybe a light coloured roof, heaps of ceiling insulation and double glazing obviously."

With a changing climate, Mr Lebo said some residents in the Whanganui-Manawatu region will experience warmer homes in the future.

Met Service meteorologist Angus Hines said temperatures around the country are expected to be warm for today before the South Island gets a slight reprieve on Friday as a cold front brings cooler air up the country.

"While Friday morning will be warm, Friday afternoon and Saturday will be noticeably cooler for pretty much the entire island, many places max temperatures dropping 10-12 degrees," he said in a statement.

The cooler front will reach the North Island over the weekend, but the temperature drop won’t be as significant.

"For northern areas temperatures will return to about summertime average, after spending this week well above average," he said.

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    1 NEWS reporter Kate Nicol-Williams spoke with eco-home consultant Nelson Lebo. Source: 1 NEWS