Do blackout curtains keep heat out? Our HVAC experts reveal everything you need to know

With heatwaves sizzling, you might be wondering, do blackout curtains keep the heat out? Luckily, the answer is yes.

Both blackout and thermal curtains have been praised for their ability to keep a home warm in warmer months, and, it turns out, they work just as well to keep a home cool in a heatwave, too.

Here, home cooling experts explain everything you need to know about making best use of blackout curtains for some summer relief.

Do blackout curtains keep heat out?

As they say, prevention is better than a cure and blackout blinds can indeed stop the heat from entering your home in the first place, by blocking the heat of the sun's rays from entering through your windows.

There is no denying that blackout curtains play a part in keeping a home cool in summer, which is especially true when paired with either some form of eco-cooling, or cooling rooms with fans.

Blackout curtains manage this due to their tightly woven fabric. The close-knit fibers are designed primarily to prevent sunlight from entering your home, working well to cool down a living room, bedroom, or kitchen.

As Lane Martin, co-founder of Modern PURAIR, advises, 'Quite a lot of people think they're just for blocking light, but they can also act as a barrier that slows heat from coming in through the windows, especially during the hottest parts of the day.

'If you keep them closed when the sun is shining directly on your windows, they'll reduce the amount of radiant heat that gets into the room.'

In fact, says Uri Pearl, owner at Nealon Insulation, they've seen rooms stay a whole 5-10 degrees cooler than usual, just by keeping blackout curtains closed during peak hours.

Lauren Fumagalli-Porter of HVAC specialists Tonna Mechanical agrees, adding that this is due to blackout curtains disrupting something called 'solar heat gain' – a process you will have noticed if you have ever walked barefoot over a section of floor that has been bathed in sunlight for an hour or so.

The process transfers the energy from the sun's rays into heat as the light hits your home’s furnishings, like your furniture, bedding, and carpets, and warms them up.

This, in turn, then warms up the air around them in your home and makes you feel hotter.

But, with blackout curtains such as the super affordable and bestselling Mainstays Solid Blackout Curtain Panel Pair available at Walmart, this process no longer occurs, making drawing them one of the fastest ways to cool down a house, and most efficient, too.

How to use blackout curtains

If you're going to install and use blackout curtains as a slightly more unusual method for staying cool at home, for maximum efficacy, it's important to do so correctly.

For example, to feel the benefit, it is best to only close the curtains when the sun is shining directly through that window.

Therefore, you should keep curtains on the east side of a house in the morning closed, and open them again in the afternoon, or leave northern windows uncovered all day, and keep southern windows covered. This will allow continuous light into your home throughout the day without contributing to any reasons your home feels hot.

This is what head of solved, Punteha van Terheyden, does in her south-facing rooms. She says, 'If I don't keep the blackout blinds we have installed in our bedroom drawn till around 4 pm, the heat in the house becomes unbearable. With them closed, even the very well-insulated upstairs area remains cool.

'As soon as the sun moves from that side, I open those blinds and windows wide to create a cross draft with the windows of the north of the house, and the entire house cools down without 10 minutes.'

It is not just any old blackout curtains that work for this, either, warns Lane Dixon, VP of operations at Aire Serv, with the quality of your window treatment ideas having a profound impact on how much heat they are able to deflect.

He explains, 'Homeowners should keep in mind that several companies manufacture blackout curtains, and reducing heat depends on the product’s quality, the home’s current insulation, window type, and other factors such as the amount of fresh air ventilation entering and exiting.'

As a result, it is important to look at the best places to buy curtains to make sure you are buying quality, without compromising on cost.

Additionally, advises John McGaughey from AUX AIR USA, 'Use ceiling fans to move air around and make rooms feel cooler without adjusting the thermostat. And don’t run heat-generating appliances like ovens or dryers during the hottest parts of the day – your AC is working hard enough already.'

What to use instead of blackout curtains

Although blackout curtains certainly help to keep heat out of your home, reflective window stickers could be a better option to help deflect heat out of your home while still letting light in. Or, for maximum efficacy, use the two together.

As Danny Pen, president of New Era Plumbing & HVAC says, 'The true power of blackout curtains lies in pairing them with reflective backing or installing them close to the window frame.

'Otherwise, heat still seeps in around the edges.'

For this, Itamar Dor of Green Life, advises, ‘These reflective window films are readily available online at sites like Amazon [such as the Kromapolis Window Film available at Amazon], and are the superior option for reflecting heat back out of your home.

‘These films are reflective on one side, allowing you to see out of your home and let some daylight in, and can be applied directly to the pane of glass, preventing thick curtains from covering open windows and blocking out a fresh breeze,’ he explains.

One thing to note about reflective films is their privacy element, which allows you to see out but stops people from looking in, only works when the outside is brighter than inside your home.

At night, for instance, when you have lights turned on in your home, the reflective quality will be reversed, allowing people to see your home. At this point, curtain ideas will be needed.

Alternatively, portable blackout curtains from Amazon, often used by moms to help their children sleep when away from home, are perfect. Punteha says, 'I swore by the suction blackout curtain packs from Amazon when my daughter was little.

'They are excellent for staying on the window and doing their job to keep the heat out, but also easy to remove or adjust for size with Velcro swatches. I used it for the first five years of my daughter's life, both in her bedroom and on vacation. I never went away without it.'

What to shop

All prices were correct at the time of publication.

FAQs

What is the difference between blackout curtains and regular curtains?

Blackout curtains are usually a lot thicker than regular curtains, with extra layers of thick material lining them to help minimize how much light can get through. Normal curtains are often thinner, with less lining material and not as densely packed. Often, you can find a spectrum of types of curtains, from full blackout to light filtering, to fully sheer, so you can dictate how much light is let into a room.

Do window blinds help keep heat out?

Window blinds can help to keep heat out to some degree, but they will not be as effective as thick curtains or window film. Blinds will work to stop the majority of the sun's rays from entering and warming up your furnishings, but the gaps between panels and loosely woven fibers mean they are far from the best way of blocking external heat from warming up your home.

Meet our experts

Lane Martin

Modern PURAIR was founded in 1969. Lane has since grown the company alongside his father, after joining in 2001.

Danny Pen

Danny leads New Era Plumbing & HVAC, a local company specializing in inspection, repair, and replacement services, for over 12 years.

Blackout curtains are a good way to start blocking out additional heat when it is warm in our home to prevent the temperature from climbing even further.

'They’re not a replacement for proper insulation or ventilation, but as a quick, passive way to take some pressure off your cooling system, they do their part,' says Lane Martin.

Therefore, they're best used in conjunction with an air conditioner, your best dehumidifier, or fans.