I put cooling home hacks to the thermal camera test – and they could save you £370

WITH the weather heating up, the internet is full of tips and tricks on how to keep your home cool – but do they really work?

The Sun tried five popular do-it-yourself tips for cooling your home – and then used a thermal camera to see how well they worked.

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We wanted to find out if they save you money on electricity by preventing you from turning on your fan or using the air conditioner.

According to the Energy Saving Trust, using a fan for 12 hours will cost between 10p and 20p, while using a portable air conditioner costs around £3 for 12 hours, based on current energy price ceilings.

During the summer, from 1 May to 31 August, the cost of using an air conditioner per day can be as high as £370, while using the fan for 12 hours a day will cost around £25.

For the tests, we used the FLIR ONE Pro Edge, which clips onto a normal smartphone and turns it into a sophisticated heat-detecting camera.

It shows the hottest areas of the home in yellow, while the warm areas are in orange and pink. Any place where hot air escapes to the outside is shown in dark blue.

The camera also measures the surface temperature of the areas we point to – meaning we can accurately calculate how active hacks are.

We asked Phil Steele, futures technologist at Octopus Energy, to give his verdict on our results:

Place ice in front of your fan

The fan moves the air around the room – this helps perspiration evaporate and helps you stay cool.

Some people recommend freezing an old plastic bottle full of water and then placing the ice bottle in front of a fan. The theory is that this makes the air colder without you having to increase the capacity.

We found this trick creates a feeling of coolness in the air – like turning on the air conditioner.

But Phil Steele says the actual difference in temperature will be minimal.

“You may end up generating more heat – and using more energy – because your freezer has to do extra work to freeze water bottles,” he warns.

• Pre-temperature: 24.3C
• Rear: 23.3C
• Change: -1C

Cover your windows with tin foil

We tested this cooling trick on windows with direct afternoon sun.

Thermal cameras showed that, before adding the foil, the area right next to the window had a sweltering temperature of 29.9 degrees Celsius.

Using a £1.75 roll of extra-wide tin foil, we cut a piece to fit the window and glued it in place by applying a few drops of water to the back. Water makes it stick to the glass.

Adding tin foil instantly made the window area cooler – and the thermal camera showed a temperature drop of 3.5 degrees Celsius.

But we don’t rate tin foil as a long-term solution on hot days because it blocks light, looks messy, and reflects light into neighbors’ windows.

“The foil will reflect heat, but that’s not a practical solution if you want to look out the window,” says Phil.

Instead, he recommends using blackout curtains, which will also reflect heat back to the outside.

He adds: “Close windows and curtains on the sunny side of the house to keep heat out and open them on the cool side to let hot air out.

• Pre-temperature: 29.9C
• Rear: 26.4C
• Change: -3.5C

Open your loft hatch

“There’s a myth that if you open your loft trapdoor, hot air gets in there because hot air rises,” says Steele.

“But in reality, hot air moves to cooler areas – and most of us have hotter lofts than the rest of the house. So if you open the loft hatch, you can see the hot air coming down.”

Our test loft got even hotter than a regular loft because it features heat-transferring Velux windows.

And when we opened the hatch, the thermal camera showed that the hatch area was much hotter when opened than closed.

The area around the loft has a pretty similar temperature, around 25 degrees Celsius – it doesn’t cool down.

• Pre-temperature: 27.1C
• Rear: 31.7C
• Change: +4.6C

Using Victorian Air Conditioners

Victorian glazed windows were designed to open at both the bottom and top, allowing hot air to escape to the top and cooler air to pass through the bottom.

“The heat rises, so if you open the top of the window, you give the heat a chance to escape,” says Phil. If you can only open one edge at a time, he recommends opening the top.

Thermal cameras have shown this in practice, with the dark blue area on the image clearly showing the greatest amount of heat lost through the top hole.

When only the bottom part of the window is open, the air in the top part of the window is a stuffy 31.7C.

But when opening both the top and bottom, the temperature dropped significantly to 25.3 degrees Celsius.

• Pre-temperature: 31.7C
• Rear: 25.3C
• Change: -6.4C

Bring a cold water bottle to bed

If you feel hot when you go to bed, a cold or frozen ‘water bottle’ can chill your bed sheets, helping you stay calm and cool at bedtime.

We used a £2.99 bag of ice – but you can simply fill a hot water bottle with ice and some water – we wrapped them in a tea towel and placed them under the blankets.

Since the package was small, we moved it every few minutes to different points on the same side of the bed.

The dark blue points captured by the thermal camera show exactly where the cooler is located – and show it to be much warmer on the other side of the bed where the cooler isn’t located.

But the benefits didn’t last long, as the area started to warm again as soon as we moved the flock.

“Unlike a hot water bottle, which will be about 30 degrees Celsius hotter than room temperature, a cold water bottle will only be about 15 to 20 degrees Celsius cooler than the bed, so it won’t make that much of a difference,” explains Phil.

“Also, a hot water bottle will cool down and your body temperature will help keep you warm. A cold water bottle heats up quickly and your body temperature will heat it up faster – so any positive effects won’t last long.”

He also warned cold water bottles would create condensation, which could cause the bed to become “soggy”.

• Pre-temperature: 25.8C
• Rear: 20.5C
• Change: -5.3C

What should you do to stay calm?

Phil recommends hanging blackout curtains (you can buy these from £15 at Dunelm and Curtains Direct) and hanging them in rooms facing the sun.

Closing windows where direct sunlight comes in also helps prevent heat from entering, and opening windows and curtains on the other side of the house helps to let out hot air.

Swap windows and curtains that you open as the sun moves during the day.

“Making sure your walls and roof are well insulated will also keep heat out, as long as you don’t let it get through the windows,” says Phil.

This is because the insulation acts like a thermos flask, retaining heat in the summer as well as in the winter.

Using these tricks with a low-energy fan can cost as little as 10 cents a day – 30 times cheaper than using an air conditioner.