In Whanganui it's feijoa season and that means the start of the colder weather.
To help local residents ward off the chill, local eco-experts have organised a pop up 'curtain bank'. It's an opportunity for the public to pick up curtains for their home, for free.
"New Zealand homes are known to be fairly cold and damp," said PNCC Eco-Advisor, Nelson Lebo. "Most older homes have single glazing."
"The fact of the matter is that high quality fitted curtains can perform just as well as double glazing."
As Palmerston North's eco-design advisor, Lebo is available for free consultations to residents, visiting hundreds of homes every year.
"Eighty per cent of the curtains I see, and I've visited over 2000 homes, are low performance curtains because the air is flowing around them," Lebo said.
This reverse chimney effect is somewthing to watch out for.
"If there's a gap at the top and a gap at the bottom, Consumer has found that they perform only slightly better than no curtain at all," Lebo said.
"As surely as warm air rises, cold air sinks, so the air in between the curtain and the window falls down to the floor. That pulls warm air off the ceiling down behind the curtain against the cold glass where it loses heat, and falls to the floor, pulling more warm air from the ceiling.
"This is why Consumer calls it the reverse chimney effect because it is driven by cold, dense, heavy, falling air."
Lebo and the Eco team say this can be solved simply by tucking the curtains up on to the sill.
"The idea is to prevent Reverse Chimney Effect. By tucking the curtains up on the window sill you're helping to prevent that down-draft.
"If the curtains are close to the glass and there's condensation we don't want the curtains to get mouldy, so first thing in the morning wipe all the condensation off. Then open your home for 10 to 20 minutes."
The Eco-Team will be back at the All Saints Hall in Whanganui East next Tuesday to hand out curtains and offer free advice on how to keep homes warm and dry, and save on power.