Consumer NZ’s latest test of window coverings finds installing well-fitted curtains and blinds will go a long way towards keeping heat inside your home.
A well-insulated home can lose about 45 percent of heat through its windows. That drops to 30 percent for an uninsulated home (but that’s only because more heat disappears through the roof and walls). The right window covering will stop nearly two-thirds of that heat from going out the window.
Honeycomb blinds were the star performer – they retained more than 60 percent of the heat lost through a bare window. Air is a good insulator, as long as it’s not moving, and the honeycomb structure creates a large, still air gap between the cold windowpane and the warm inside air.
If you prefer curtains, Consumer NZ head of testing Dr Paul Smith said you were best off going heavy and long.
“Our test shows heavy lined curtains are better than the coated thermal-backed types and, for the best result, you should fit them down to the floor instead of stopping them at the sill,” he said.
Regarding blinds, Dr Smith said it was essential they were fitted properly.
“You want them close to the window and within the frame – aim to minimise gaps at the top, bottom and at the sides. Honeycomb blinds topped our test, but we found roman blinds and roller blinds were effective as well, as long as they were fitted correctly. Even venetians worked – but keep those slats closed,” he said.
“However, regardless of personal preference or budget, any curtains and blinds are better than nothing. If you’ve got any uncovered windows, put up something.”
Consumer NZ also investigated a few cheap “hacks” to improve your curtains this winter. While it wasn’t the most convenient solution, hanging a blanket behind curtains lifted heat retention dramatically. Even easier, but less effective at keeping your home toasty, was rolling up a towel and placing it on top of the curtain rail.
To make the best use of your curtains and blinds, Consumer NZ advises people keep them open during the day over winter to make the most of the sun. Close them as soon as the sun sets to trap as much heat as possible. You should also fix any draughts in the windows – you can detect them with a lit candle.
To see the full results of Consumer NZ’s curtains and blinds test, check out the June/July issue of Consumer magazine or visit consumer.org.nz.
About Consumer NZ’s test
We measured heat loss through an aluminium-framed single-glazed window, fitted to a mini-room inside our Thermal Comfort lab. The lab temperature was reduced to 4°C to simulate a chilly winter night, while an electric heater inside the mini-room beavered away to maintain a temperature of 20°C. The different window coverings were tested for at least three hours and we measured the total power usage from the heater, along with the difference between indoor and outdoor temperature.