The 'heat sink' effect is ruining your sleep, here's what it is and why moving your bed can fix it

It’s very hot in the UK right now - understatement of the century but it’s true. But as one of the hottest Junes on record continues to hurtle on, with many more heatwaves bound to take place over this summer, we’re all looking for any way to stay cool - but especially when sleeping.

Despite the use of strong fans, wet flannels and copious thoughts and prayers, sleeping in this heat is nary impossible. So any hack to help elevate the strain on our bedrooms this summer is worth trying, and I’ve discovered something that could be the reason your bedroom in particular feels like a furnace.

It’s called the ‘heat sink’ effect, but as scary and sweaty as it might sound, there is one handy trick that takes two seconds and could make all the difference in helping you avoid the sink and finally get a good night’s sleep this heatwave.

What is the ‘heat sink’ effect?

The "heat sink effect" is a phenomenon where a surrounding material absorbs and rapidly draws thermal energy away from a concentrated heat source, typically due to high thermal conductivity or mass. But to put that in better phrasing that doesn't require a science degree to decode; it basically means when heat spreads into nearby materials instead of staying concentrated in one area.

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But what does that mean for you and your bedroom, well it’s simple. The heat sink effect can help explain why a bedroom stays hot during a heatwave, even after the outdoor temperature starts to drop. Throughout the day, your walls, floors, ceilings, furniture, and other materials in the room absorb heat from the sun and warm air. These materials effectively act as heat sinks, storing thermal energy and slowly releasing it back into the room over time, and subsequently onto you.

As a result, the bedroom can continue to feel uncomfortably warm well into the evening and overnight because the heat isn't just coming from the air outside - it's also literally radiating from all the surfaces that have been heating up throughout the day. And that’s why you feel like you’re slowly being microwaved while you attempt to sleep.

The bed trick

The simple move that can make a pretty sizeable difference when it comes to feeling the effects of the heat sink is to move your bedroom away from walls, especially exterior ones or anything in direct sunlight.

During a heatwave, walls exposed to direct sunlight can absorb large amounts of heat throughout the day. Even after the sun sets and outdoor temperatures begin to fall, those walls continue releasing the stored heat back into the room.

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When your bed is positioned directly against or very close to a warm wall, you're effectively sleeping next to a large surface that's radiating heat. This can make the area around your bed feel noticeably warmer than the rest of the room and make it harder for your body to cool down naturally as you sleep.

By pulling the bed even a few inches away from the wall, you create an air gap that helps reduce the transfer of heat from the wall to your sleeping space. The extra airflow also allows warm air to dissipate more easily rather than becoming trapped between the mattress and the wall. While it won't eliminate the heat entirely, this simple trick can make a surprising difference in comfort during hot summer nights, of which we still have plenty to come - so if I were you, I’d get shifting that furniture ASAP.

More ways to beat the heat sink effect

Keep curtains or blinds closed during the hottest parts of the day to prevent sunlight from heating walls, floors, and furniture.
Ventilate the room when outdoor temperatures are cooler than indoor temperatures. While opening your windows during peak heat times is a bad idea, letting hot air rush through your home, opening up late at night or early in the morning is essential.
Use a fan to circulate air and prevent pockets of warm air from building up near walls and ceilings.
Reduce heat generated indoors by turning off unnecessary electronics and lights.
Sleep lower to the ground, where possible as hot air naturally rises.
Avoid placing large heat-retaining items, such as dark furniture or bulky storage units, near the bed.