How to Keep Your Home Cool Without Air Conditioning

Why Do Some UK Homes Overheat?

A home can absorb solar heat through its windows, roof and walls throughout a sunny day, then release some of that heat indoors into the evening. A top-floor flat, a west-facing bedroom with large unshaded glazing or a property with windows on only one side may be harder to cool naturally. Dense urban surroundings and restricted window opening can make matters worse. [1]

Good winter insulation is not necessarily a summer problem. It can slow heat entering as well as escaping, but overheating can still occur when solar gain, indoor heat sources and poor opportunities for ventilation overwhelm the home. The position and size of windows, shading and safe night-time airflow matter. [1] [4]

Notice the hottest room, the time it becomes uncomfortable, which windows receive direct sun and whether temperatures fall overnight. A simple indoor thermometer can help you compare conditions; it does not diagnose the building's full thermal performance.

• Top-floor rooms and homes with large sunny windows may accumulate heat.
• Rooms with openings on only one side may have limited cross-ventilation.
• Unshaded east- and west-facing windows can create uncomfortable morning or evening heat.
• Some occupants, including older people, young children and people with health conditions, face higher health risks in hot weather. [1] [2]

First: Keep Sunlight Out Before Rooms Heat Up

Closing curtains, blinds or shutters on windows receiving direct sunlight can reduce the solar heat coming through the glazing. Ideally, lower the shades before the room becomes hot; use other windows for safe ventilation if their outside air is cooler. [1] [2] [5]

External shading, such as an awning, exterior shutter or appropriately placed planting, can intercept sunlight before it passes through glass. Internal curtains and blinds are useful and easier for many households to install, though the performance depends on colour, fit, glazing and window orientation. Do not assume a decorative shade is equivalent to a measured overheating solution. [1] [4]

If you are renting, start with non-permanent measures and check your tenancy agreement and seek written permission before permanent external shading or glazing work. Keep escape routes, window restrictors and essential ventilation functional.

• Draw blinds or curtains on sun-facing windows in the hottest hours.
• Use existing shutters or external shades when available.
• Plan extra shading for rooms that repeatedly overheat, especially bedrooms.
• Before buying permanent products, consider permissions, wind resistance, light and safe window access. [1] [1]

Second: Let Cooler Air In at the Right Time

If it is hotter outside than inside, opening all the windows can let more heat into the home. During the hottest part of the day, it may be better to shade windows and keep hotter outdoor air out. Once the air outside feels cooler than indoors, opening safe windows can help release stored heat. Early mornings and evenings are often useful opportunities. [1] [2] [5]

Where a home has safe openings on different sides, airflow through the property may help. But night ventilation must take account of security, ground-floor access, child safety, window restrictors, traffic fumes, noise and individual circumstances. Do not leave an accessible window open if doing so is unsafe. [1] [4]

Keep purpose-designed mechanical ventilation operating in accordance with its instructions. Ask the installer whether it has a suitable summer bypass or summer operating mode rather than turning it off without understanding its function. [1]

Third: Reduce Heat Produced Inside

Ovens, tumble dryers, lighting and electronics add heat while operating. Where convenient, cook during cooler hours, cover pans, prepare no-cook meals and turn off unnecessary lights or devices. Check that space heating is not inadvertently on. These changes are usually modest individually but can help in a very hot room. [1] [2] [5]

Move work or rest to a shaded room where practical, particularly during the hottest afternoon hours. If a bedroom remains very hot, a safer, cooler room may be the better place to sleep temporarily. Do not obstruct vents or turn off essential appliances, medical equipment or refrigerators to save energy. [1] [2]

For households using fans or other cooling equipment, consider electrical loading and cable safety. Do not drape cloths over equipment or block ventilation slots. [2]

Do Fans Cool a Room?

A conventional desk, tower or pedestal fan mainly moves air across the skin, helping sweat evaporate and making a person feel cooler. It does not normally reduce the room's air temperature; the motor itself releases some heat. Fans can be a relatively low-cost way to improve personal comfort, especially when combined with shading and cooler outside air. [5]

UK Health Security Agency guidance for England recommends using electric fans when the air temperature is below 35°C and advises against directing them straight at the body because dehydration can become a concern. Fan use is not a substitute for fluids, moving to a genuinely cooler environment or seeking help for heat illness. Higher-risk residents should follow current NHS and public-health advice. [1] [2] [3]

Do not assume that an expensive bladeless or designer fan is automatically cheaper to run. Check rated wattage and the operating setting. If the fan is aimed at nobody in a closed room, it is not providing the same personal cooling benefit as when someone is present. [5]

• Best use: improving personal comfort through air movement.
• Limit: it does not provide refrigerated cooling of the room.
• Safety: follow the public-health temperature advice, keep hydrated and supervise children around fans. [2] [3] [2] [3]
• Cost: look at the appliance's wattage, duration of use and your electricity unit rate.

How Much Do Cooling Devices Cost to Run?

Energy Saving Trust’s UK comparison, updated in October 2026 and checked on 1 November 2026, estimates typical costs for 24 hours of use. For Great Britain, a fan was approximately £0.14–£0.30, an evaporative cooler £0.27–£0.39, and a portable air conditioner £4.62–£5.00. The same comparison put Northern Ireland fan costs at £0.17–£0.37, evaporative coolers at £0.34–£0.48, and portable air conditioning at £6–£7. These are dated illustrative ranges, not current product prices or guaranteed costs for your home. [5]

As a separate calculation example, a 40-watt fan used for eight hours consumes 0.04 kW × 8 hours = 0.32 kWh. At a fictional 25p per kWh, this works out to 8p for that use, excluding any daily standing charge that applies regardless. A 1,000-watt appliance running at full power for eight hours would use 8 kWh and cost £2.00 at the same fictional rate; actual portable cooling equipment may cycle rather than run continuously at full load.

To estimate your own costs: watts ÷ 1,000 × hours used × your electricity rate in pounds per kWh. Separate capital purchase costs from electricity running costs, and check the appliance specification rather than relying on marketing descriptions. [5]

• Fan: mainly improves personal comfort; typically lower electricity consumption.
• Evaporative air cooler: may cool nearby air but adds moisture and works less well when the air is humid.
• Portable air conditioner: actively cools indoor air, but usually consumes substantially more electricity.
• The most cost-effective first step may be shading and timed ventilation rather than buying a device.

What About Evaporative Air Coolers?

Evaporative coolers use water evaporation to cool the air passing through them. Unlike an ordinary fan, they may lower nearby air temperature in suitable conditions, but they add moisture to the room. Their effectiveness falls when the surrounding air is already humid. [5]

If your home has condensation or mould problems, adding moisture may be particularly unsuitable. Follow product instructions for water hygiene, cleaning and ventilation, and do not expect the same cooling as a refrigerated air conditioner. [5]

Before purchasing, ask whether the room can be ventilated safely, whether you need personal comfort or a measurable fall in temperature, and what the product's actual power rating and water requirements are. [5]

How to Keep Bedrooms Cooler Overnight

Bedrooms can remain uncomfortable even after sunset because furniture, walls and the roof release heat accumulated earlier. Shade the room before midday or before direct afternoon sun reaches the glazing. When the air outside cools and it is safe, use windows to exchange warmer indoor air for cooler air. [1] [2]

Consider lighter bedding and, where feasible, sleeping in a cooler room. If you care for a baby, follow NHS guidance on safe room temperatures, bedding and overheating; a fan should not be directed at the baby. People with additional medical needs should seek appropriate personalised advice. [3] [6]

When outdoor air stays very hot, passive measures may not be enough. Spend time somewhere cooler if you can do so safely, and check on household members and neighbours who may need assistance. [1] [2]

When Heat Becomes a Health Emergency

Heat exhaustion can involve dizziness, headache, nausea, heavy sweating, thirst and weakness. Move the person to a cooler place, remove unnecessary clothing, offer fluids if they can drink safely and cool the skin. NHS guidance says symptoms should begin improving within about 30 minutes. If symptoms are difficult to manage, contact NHS 111. [3]

Heatstroke is an emergency. Warning signs can include confusion, loss of coordination, very high temperature, fast breathing, seizures or loss of consciousness. If heatstroke is suspected, call 999 and begin cooling the person while waiting for help. Do not delay emergency action while trying to cool the house. [2] [3]

Keep an eye on people at greater risk, including older residents, very young children, pregnant people and those with relevant medical conditions. A property that stays dangerously hot may require a genuinely cooler location and professional advice rather than reliance on a fan alone. [1] [2]

Longer-Term Improvements for Repeated Summer Overheating

If the same rooms overheat every summer, consider whether exterior shading, solar-control glazing, improved secure ventilation or an overheating-aware renovation would provide a more lasting solution. Review the exposure of each window and the practical limits of your home before choosing equipment. [1] [5]

Insulation can reduce winter heat loss and sometimes slow incoming summer heat, but its effect on overheating depends on sun exposure, ventilation and construction. Do not assume adding insulation alone will make an already hot upper floor comfortable. For major works, ask a qualified designer or installer how summer conditions and moisture will be addressed. [1] [5]

England's Approved Document O is a technical standard for new residential buildings, not a blanket retrofit requirement for every existing house. Planning, landlord, building safety and other requirements vary by work and UK nation. Ask for project-specific advice before fitting external shutters, permanent air-conditioning plant or making structural changes. [7]

Your Practical Summer Cooling Checklist

Start with measures that cost little or nothing, reassess the result, and only then consider purchasing equipment. If someone is becoming unwell in the heat, prioritise immediate health measures over this sequence.

• Note which rooms overheat and when the sun reaches their windows.
• Shade sun-facing windows before the room becomes hot.
• Keep hotter outdoor air out; ventilate when outside air is cooler and opening windows is safe. [1] [1]
• Turn off avoidable sources of indoor heat and check heating is off.
• Use fans for personal comfort within current heat-health guidance, not as a substitute for safe indoor temperatures. [2] [2]
• Check on higher-risk occupants and know the signs of heat exhaustion or heatstroke. [2] [3] [2] [3]
• Compare appliance wattage, purchase costs and electricity running costs before buying a cooler.
• For persistent overheating, get property-specific advice about secure airflow, solar shading and building upgrades.