(First published September 2008, last updated January 2013)

A recent heatwave reminded me that I need to get some blackout curtains for a few windows of my new digs. During the hottest part of the day, even without the sun directly shining on the glass, the amount of heat being radiated from these windows was amazing.

Blackout curtains just aren’t for blocking light or for summer conditions; they can be useful during winter too.

Around a third of home heating and cooling related energy loss occurs via your windows. Blackout curtains can help insulate your home, saving you money in heating and cooling and the energy savings can also assist in reducing greenhouse gas emissions associated with energy production and consumption.

Additionally, as blackout curtains are much heavier than normal curtains and assuming decent quality materials are used; you can expect them to last a long time.

How do blackout curtains work?

Blackout curtains have a backing that is made from a very tightly woven fabric, usually multiple layered, which blocks most of the light; with some brands claiming up to 99.9%. reduction

How much energy can be saved?

According to some manufacturers, blackout curtains can reduce thermal loss by up to 25%. If you’re spending a few thousand dollars a year on heating and cooling, the savings add up quite quickly and can offset the cost of the curtains within a short space of time.

Other benefits of blackout curtains

I hate noise.. I mean really, really hate it. Noise pollution is a major problem for many people and is one of the most underrated environmental threats. Excess noise has negative physical and psychological effects on people and animals. It seems there’s no peace in the burbs any more, even when we need it most –  at night time when we’re trying to sleep. Blackout curtains won’t soundproof a room, but they can help significantly reduce the noise level.

How much do blackout curtains cost?

This varies greatly with size and quality of materials of course, but for a set of 2 curtains 180cm ( 6ft) x 230cm (7.5ft); expect to pay around $50 – $75.

If you’re handy with a sewing machine you can also save a bit of money by converting your current curtains – just add the blackout liners that you can buy from a haberdashery store. As there’s varying quality in blackout liners, be sure to hold samples up to a strong light before purchasing to ensure it works sufficiently.

Blackout curtain tips

A couple of simple tips for using blackout curtains that will maximize your energy and greenhouse gas emission savings:

To get the most from blackout curtains, you need to ensure the gather is sufficiently high above the rod to block light from appearing at the top and that the rod is situated so that it minimizes the amount of light “leaking” out the sides.

During the cooler months, only have the curtains open when the sun is shining into the room or outside temperatures are warmer than inside. During summer, curtains should be kept closed as much as possible; even if the sun isn’t shining directly upon the window.