Air Conditioning for Bedrooms

Britain's housing stock was built to hold heat in. That's excellent for eleven months of the year and miserable for the other one.

Bedrooms suffer worst. They're usually upstairs, where heat collects, often under a roof that's absorbed sun all day, and you're trying to use them at the hottest part of the twenty-four hour cycle.

Why sleep goes first

Your body needs to lose heat to fall asleep and to stay asleep. Sleep research generally puts the comfortable bedroom range at around 16–19°C. A British bedroom in a heatwave can be closer to 28°C at midnight, and still above 25°C at four in the morning because the building hasn't had time to cool.

That's why a hot night doesn't just feel unpleasant — you wake repeatedly, and you're tired for days afterwards.

Why fans don't fix it

A fan doesn't lower the temperature. It moves air across your skin, which helps you lose heat by evaporation — genuinely useful up to a point.

Past roughly your own body temperature, that stops working and a fan is essentially blowing hot air at you. It also adds a small amount of heat to the room from the motor.

Fans are cheap and worth having. They aren't a solution to a genuinely hot room.

Why portable units disappoint

Portable air conditioners need to exhaust hot air somewhere, which means a hose through a partly open window.

That gap is the problem. The unit pushes air out of the room, so air gets pulled in from outside to replace it — warm air, all night. You end up with a machine fighting a leak it created.

They're also noisy, because the compressor is in the room with you rather than outside. For a bedroom that matters more than anywhere else in the house.

What a fixed system does differently

The compressor — the noisy part — lives outside. Indoors there's just a fan moving air over a cold coil, and modern units run very quietly on their lowest setting. Quieter than a fridge, and quiet enough to sleep through.

There's no open window, so no warm air being drawn in. And because it dehumidifies as it cools, the room feels comfortable rather than just cooler.

Practical notes for bedrooms

• Don't set it too cold. Around 19–21°C is usually right. Too cold and you'll wake up.
• Use the sleep or quiet mode. Most systems have one that drops fan speed and gently adjusts the temperature overnight.
• Position matters. You don't want air blowing directly onto the bed. Tell your surveyor where the bed goes.
• Run it before bed. Cooling a hot room takes time. Starting an hour before you go up works better than starting at bedtime.
• Remember the winter side. The same unit warms the room on cold mornings, which for many people ends up being the half they use most.