How to Cool a Room in the UK: 12 Methods That Actually Work
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Key Takeaways |
| ✅ Keep windows closed during the hottest part of the day (typically 11am–6pm) — opening them lets hot air in. ✅ Open windows wide on opposite sides of the house overnight to flush stored heat out of the building fabric. ✅ Blackout or reflective blinds make a bigger difference than most people expect — solar gain through glass is a major heat source. ✅ Fans don’t cool the air — they cool you by speeding up sweat evaporation. Point them at people, not rooms. ✅ A portable air conditioner is the only device that actually lowers room temperature — everything else manages comfort. ✅ Dehumidifiers help if the air feels muggy and sticky (above 60% RH) — they don’t cool the room but reduce perceived heat. ✅ Upstairs rooms are always hotter — hot air rises and heat accumulates in the roof space throughout the day. |
How to cool a room in a UK heatwave is one of those things that sounds simple until you’re lying awake at 1am in a 28°C bedroom wondering what you’re doing wrong.
The honest answer: most UK homes aren’t built for heat. Solid brick and stone construction holds warmth well into the night, upstairs rooms trap heat under the roof, and we rarely have air conditioning. You’re working against the building as much as the weather.
The good news is there are methods that genuinely work — and some that don’t, despite being widely repeated. This guide covers both, ranked roughly by effectiveness, so you can focus on what actually makes a difference.
First: Understand How Heat Gets Into Your Home
Before diving into fixes, it helps to know where the heat is coming from. In a UK heatwave, your home gains heat through three main routes:
Solar gain through windows: Sunlight passing through glass heats up surfaces inside the room — floors, furniture, walls. This is often the biggest single source of heat in sunny rooms.
Hot air entering through gaps and open windows: When outdoor air is warmer than indoor air, ventilation works against you. Opening windows during the day in a heatwave can make rooms hotter, not cooler.
Internal heat sources: Appliances, lighting, cooking, and even body heat all add to the thermal load. Less significant than the first two, but worth minimising during a heatwave.
Most effective cooling strategies address at least one of these directly.
12 Ways to Cool a Room in the UK
1. Close Windows During the Day
This is the most counterintuitive and most important tip. If outdoor air is warmer than indoor air — which it usually is from mid-morning onwards during a heatwave — opening windows makes rooms hotter, not cooler.
Keep windows closed and covered from around 9–10am until the outdoor temperature drops below the indoor temperature, typically early evening. Check a weather app for hourly temperatures to time this accurately.
2. Cross-Ventilate Overnight
Night-time is your opportunity to reset the building. Open windows on opposite sides of the house to create a through-draught — this is sometimes called cross-ventilation or, as it is known in Germany, Querlüften. The goal is to flush the heat stored in walls, floors, and furniture out of the building before the next day’s heat arrives.
Do this as soon as outdoor temperature drops below indoor temperature in the evening. Close everything up again in the morning before the outdoor air warms up.
| Opening the loft hatch at night can help — hot air rises and the loft is often the hottest space in the house. As warm air rises into the loft, cooler air is drawn up from below. Only do this once the sun is off the roof, otherwise you push roof heat downward into your living spaces. |
3. Block Solar Gain With Blinds or Curtains
Unshaded south or west-facing windows can raise a room’s temperature significantly during a heatwave. The most effective solution is a white or silver reflective blind fitted snugly within the window reveal — this bounces solar radiation back out before it can heat the room.
Dark curtains absorb solar heat and re-radiate it into the room — better than nothing, but less effective than reflective blinds. External shutters or awnings are more effective still, but less practical for most UK homes.
Keep south and west-facing rooms closed off and shaded from late morning until the sun moves off those windows in the afternoon.
4. Use a Fan Strategically
Fans are widely misunderstood. A fan does not cool the air in a room — if you leave a fan running in an empty room, the temperature will actually rise slightly due to the motor heat. What fans do is cool people, by speeding up the evaporation of sweat from skin.
This means placement matters: point the fan at the people in the room, not at the walls. Ceiling fans should run anticlockwise in summer (on the standard setting) to push air downward.
At night, positioning a fan to draw cooler air in from an open window can help — but only when outdoor air is genuinely cooler than indoor air.
| ⚠️ Fans and hot outdoor air: placing a fan in a window during the day when outdoor air is hot will pull hot air into the room and make it worse. Fans only help with ventilation when outdoor air is cooler than indoor air. |
5. Reduce Internal Heat Sources
Appliances, lighting, and cooking all add heat to the room. During a heatwave, small changes make a meaningful difference:
• Switch to LED lighting if you haven’t already — incandescent and halogen bulbs waste most of their energy as heat
• Avoid using the oven — cook outside, use a microwave, or eat cold meals during the hottest days
• Turn off TVs, computers, and other electronics when not in use — they generate more heat than most people realise
• Run washing machines and dishwashers in the evening rather than during the day
6. Cool Yourself, Not Just the Room
During a heatwave, direct body cooling is often more practical than trying to cool the entire room:
• Cold water on pulse points (wrists, neck, temples) — blood vessels close to the surface cool quickly
• Light, loose, natural-fibre clothing (cotton or linen)
• A damp flannel on the forehead or neck
• Stay hydrated — dehydration makes heat much harder to tolerate
• Cool showers, especially before bed
7. Run a Dehumidifier if the Air Feels Sticky
If your home feels humid and muggy as well as hot — that sticky, airless feeling — running a dehumidifier can improve comfort significantly. High humidity prevents sweat from evaporating properly, which is what makes humid heat feel so oppressive.
Check your indoor relative humidity with a hygrometer. If it reads above 60% RH, a dehumidifier is likely to help. If it reads below 50% RH, the air is already reasonably dry and a dehumidifier won’t make much difference.
Our top pick for most UK homes is the Meaco MeacoDry Abc 12L — quiet, efficient, and well-suited to summer use.
| Note: a dehumidifier does not lower air temperature — it makes the air drier, which makes the heat feel more manageable. It is not a substitute for cooling. |
8. Freeze or Chill Your Bedding
Putting a pillowcase or light sheet in a sealed bag in the freezer for 30–60 minutes before bed won’t last all night, but can make the critical first 30 minutes of trying to sleep much more comfortable — often enough time to drift off.
9. Move to the Coolest Room
Upstairs rooms are almost always hotter than downstairs during a heatwave. Heat rises, and the roof absorbs and stores solar energy throughout the day. If you have a ground-floor room that is cooler, consider sleeping there temporarily during a heatwave.
North-facing rooms are typically the coolest — they receive the least direct sunlight throughout the day.
10. Create a DIY Ice Fan
A bowl of ice placed in front of a fan creates a simple evaporative cooling effect. As air passes over the ice and melts it, it picks up some coolness. The effect is modest and short-lived, but useful for a short burst of cooler air — in a small room or directly in front of the fan.
This works better in dry air than humid air. In a very humid room, the ice melts quickly and adds moisture to the air without much cooling benefit.
11. Use a Portable Air Conditioner
A portable air conditioner is the only device on this list that actually lowers room temperature. Everything else makes you feel cooler or prevents the room getting hotter — a portable AC removes heat from the room and vents it outside.
The trade-off: portable ACs need a vent hose routed to the outside (through a window, door, or wall), they use significantly more electricity than a fan, and they’re bulky. But during a prolonged heatwave, they make a genuine, measurable difference.
| Model | Cooling Capacity | Best For | Noise |
| De’Longhi Pinguino PACEX100 | 10,000 BTU | Running cost leader — most energy efficient | ~44 dB |
| Dreo AC515S | 10,000 BTU | Noise leader — quietest portable AC | ~42 dB |
| Meaco MeacoCool MC Series | 9,000–12,000 BTU | All-round performance, UK brand support | ~46 dB |
| Olimpia Splendid Dolceclima Compact | 8,000 BTU | Compact rooms, easy setup | 63 dB (sound power) |
| Pro Breeze 9000 BTU 4-in-1 | 9,000 BTU | Budget option, 4-in-1 functionality | ~65 dB |
⚠️ Olimpia Splendid noise: the 63 dB figure is sound power (Lw), not sound pressure (Lp). Sound power cannot be directly compared with the dB figures quoted by other manufacturers — in practice the Olimpia Splendid is not as loud as this figure suggests, but direct comparisons are not possible. ⚠️ Pro Breeze noise: at ~65 dB sound pressure, the Pro Breeze 9000 BTU is not suitable for overnight bedroom use. |
12. Combine Methods for Maximum Effect
No single method below a portable AC will transform a hot room on its own. The biggest gains come from combining approaches:
• Close and shade windows during the day to prevent heat entering
• Cross-ventilate overnight to flush stored heat out
• Use a fan to keep air moving and aid sweat evaporation
• Run a dehumidifier if humidity is above 60% RH
• Reduce internal heat sources where possible
Method Comparison: What Each Approach Actually Does
| Method | Lowers Temp? | Improves Comfort? | Cost | Best Use |
| Close windows daytime | Prevents rise | Yes | Free | All rooms during heatwave |
| Cross-ventilate overnight | Yes (resets overnight) | Yes | Free | All homes — most important tip |
| Reflective blinds | Prevents solar gain | Yes | Low | South/west-facing rooms |
| Fan | No | Yes (cools people) | Very low to run | Any room with people in it |
| Dehumidifier | No | Yes (if humid) | Low to run | Muggy, sticky rooms above 60% RH |
| Portable AC | Yes | Yes — directly | Higher to run | Rooms that are genuinely too hot |
| Ice fan (DIY) | Marginally | Briefly | Free (ice cost) | Small rooms, short-term relief |
| Body cooling | No (body only) | Yes — directly | Free | Immediate personal relief |
How to Cool a Bedroom for Sleep
Bedrooms — particularly upstairs ones — are the hardest rooms to keep cool during a UK heatwave. Heat rises, roof space stores solar energy all day, and by bedtime the fabric of the building is at peak warmth.
The most effective bedroom cooling strategy:
During the day: Keep the bedroom door and windows closed. Fit blackout or reflective blinds and keep them down on sun-facing windows. Don’t use the room — let it sit undisturbed.
Early evening: Once outdoor temperature drops below indoor temperature, open windows fully on opposite sides of the house. Let the cross-draught flush the stored heat out for at least an hour before bed.
At bedtime: Use a fan positioned to draw cooler air across your body. Sleep with light cotton bedding. Use chilled pillowcases if needed.
If none of this is enough: A portable air conditioner is the only reliable solution for a bedroom that is genuinely too hot to sleep in. The Dreo AC515S is the quietest option available — important for bedroom use.
| Health Note |
| NHS guidance: prolonged exposure to temperatures above 24°C at night is associated with reduced sleep quality. Above 26°C, the health impact becomes more significant, particularly for elderly people, young children, and those with pre-existing health conditions. |
How to Cool an Upstairs Room
Upstairs rooms accumulate heat from two directions: warm air rising from the floors below, and solar heat radiating down through the roof. On a hot day, loft spaces can reach 50°C+, and that heat conducts downward into the rooms below.
Additional steps for upstairs rooms:
• Open the loft hatch at night (once the roof has cooled) to allow hot air to escape upward
• Ensure loft insulation is in good condition — it works both ways, slowing heat transfer into the room below
• If the room has a skylight, consider a reflective blind or blackout cover — skylights admit direct overhead sunlight and can be a major heat source
• A portable AC is more effective in upstairs rooms than downstairs because the temperature differential is greater
Frequently Asked Questions
Does putting ice in front of a fan cool a room?
Slightly and briefly — it creates a localised evaporative cooling effect. The fan blows air over the ice, which picks up a small amount of coolness as the ice melts. The effect is modest, works better in dry air than humid air, and lasts only as long as the ice. It won’t cool an entire room but can provide short-term relief directly in front of the fan.
Should I open windows at night during a heatwave?
Yes — but only once outdoor air is cooler than indoor air, which typically happens from early evening onwards during a UK heatwave. Opening windows on opposite sides of the house to create cross-ventilation is the most effective free method for resetting your home overnight. Close everything up again before the outdoor temperature rises in the morning.
Does a dehumidifier cool a room?
No — a dehumidifier removes moisture from the air, not heat. It can make a room feel more comfortable if the air is humid (above 60% RH), because drier air allows sweat to evaporate more efficiently. But it will not lower the thermometer reading. See our full guide: Does a Dehumidifier Help in a Heatwave?
How do I cool a room without a window?
Rooms without openable windows are difficult to ventilate. Focus on reducing heat sources (lights, appliances), using a fan for personal cooling, and if the heat is severe, a portable air conditioner — some models can be vented through a wall or ceiling rather than a window. See our guide: How to Vent a Portable AC Without a Window
What is the fastest way to cool a room?
The fastest way to lower room temperature is a portable air conditioner — it can drop room temperature by several degrees within 30–60 minutes. For immediate personal cooling without an AC, a fan combined with cold water on pulse points (wrists, neck) is the quickest free option.
Why is my upstairs so much hotter than downstairs?
Hot air rises and accumulates at ceiling level, then in the floor space above. The roof also absorbs solar radiation all day and conducts that heat downward into upper rooms. By evening, an upstairs room can be 4–6°C hotter than the ground floor. Cross-ventilating overnight and opening the loft hatch after dark are the most effective free remedies.
Does turning on more fans make a room cooler?
Not really. Multiple fans increase air movement, which can make more people feel cooler — but the additional motor heat from each fan slightly raises the room temperature. Fans cool people, not rooms. One well-positioned fan is usually more effective than several poorly positioned ones.
Quick Decision Guide
| What Is Your Situation? |
| My room feels hot and stuffy → Start with overnight cross-ventilation and blackout blinds during the day. These are free and make a significant difference. My room feels hot AND humid/sticky → Add a dehumidifier. Check your RH — if above 60%, the Meaco MeacoDry Abc 12L will help. I need to cool a specific person (not the whole room) → Fan pointed directly at them. Faster and cheaper than any other option. My bedroom is too hot to sleep in → Cross-ventilate overnight, use reflective blinds during the day, fan at night. If that is not enough, the Dreo AC515S is the quietest portable AC for bedroom use. I need the room genuinely cooler, not just more comfortable → Only a portable AC will lower the thermometer reading. The De’Longhi Pinguino PACEX100 is the most energy-efficient option. |
Related Articles
• Best Portable Air Conditioner UK — full roundup with honest verdicts on every major model
• Does a Dehumidifier Help in a Heatwave? — when a dehumidifier actually helps and when it won’t
• How to Vent a Portable Air Conditioner Without a Window — options for rooms without openable windows
• Best Portable Air Conditioner for a Bedroom UK — noise-tested picks for sleeping through the heat
• Best Hygrometer UK — measure your indoor humidity to know if a dehumidifier will help
| About This Article |
| About this article: Written by the UK Air Quality editorial team. We research and evaluate dehumidifiers, air purifiers, and cooling products for UK homes. Our recommendations are based on hands-on assessment and publicly available technical data. Sources and further reading:• British Red Cross — keeping your home cool in a heatwave: redcross.org.uk• NHS — heatwave health advice and sleeping in the heat: nhs.uk• UK Met Office — heatwave guidance and UK temperature data: metoffice.gov.uk• UK Health Security Agency — heat health alert guidance: gov.uk/ukhsa |
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