Palmerston North's John Hornblow took the advice of eco design adviser Nelson Lebo about how to cool the house down at night, and it worked. Photo: Murray Wilson/ Fairfax NZ People tired of battling the heat to get a good night’s sleep could take a tip from New Zealand-based eco design adviser Nelson Lebo – turn the fan around.
Point it out the window to blow the hot air out, and open a window on the shady side of the house to draw the cool air in.
“It really is the best, low-cost, highly effective technique to keep a home cool, but it is virtually unknown,” Lebo said.
He said people should set up the fan as soon as the outdoor temperature dropped lower than that in the house.
PNCC Eco Design Adviser Nelson Lebo about how to cool the house down at night. Photo: David Unwin/Fairfax NZ
He recently consulted John and Jenny Hornblow about what they could do to relieve the upstairs heat in their Palmerston North home.
As a start, he picked up the fan they had directed toward the bed, took it to another room, and pointed it out the window. A single open window in their room set up the through draft.
“It’s brilliant,” Hornblow said. “It dropped the temperature in our room significantly.
“We had a comfortable night’s sleep because we were getting the outdoor temperature in our room, not just circulating warm air. And it cost about 10c to have the fan running.”
He said every home in Palmerston North could benefit from the eco design service that the city council provided free for residents.
“Nelson is so sensible and practical, with so much technical knowledge and experience, and his explanations made it completely understandable.”
Lebo said turning the fan around seemed counterintuitive to most people.
While it was true that air movement gave the illusion of cooling the skin, the fan was not cooling the air or drawing cool air into the house if used that way.
In a variation of fan theme, Lebo said sceptics could carry out a simple experiment.
After sunset, close the windows, except for one in the bedroom, and turn on the bathroom extractor fan.
“You will get the best night’s sleep ever.”
The theory was the same, whether it was using the kitchen extractor to remove cooking heat and smells, the bathroom fan to take away steamy air, or the fan in the window. Hot air out, cool air in.
The next trick was to delay the house from heating up during the day.
“Treat your house like a chilly bin [esky].”
Having brought the cool night air in, try to keep it there. Keep doors and windows closed, otherwise hot air comes in. And close the curtains against the sun — on the east-facing windows in the morning, and on the west once the sun moves around.
The role of curtains reversed in summer. Instead of keeping warm air in at night, they should be used in the day to keep the heat out. Curtains long enough to sit on the floor actually worked.
Lebo said people put up a range of objections to his advice, and it was up to different families in different houses how to balance comfort against other priorities.
Open windows could mean inviting flying insects in, but screens were not expensive or difficult to install.
Security concerns could be overcome with safety catches.
And if teenagers wanted to close their doors and miss out on the cool draft, there should be a no whingeing rule.
However, cross ventilation could be achieved in any room that had two windows.
Lebo said basic fans were not expensive, and his own model made less noise than the fridge and freezer motors.
Keep cool tips:
– Turn the fan around to blow hot air out the window.
– Open a window on the cool side of the house to allow cool air in.
– Close doors and windows during the day to keep the heat out.
– Draw curtains to keep the sun out.
– Leave curtains not needed for privacy open at night to allow hot air to escape.
– Have your next curtains made to sit right down on the floor.