How to cool down a room: seven strategies to keep your home cool throughout the summer

Several factors influence the temperature of the rooms in your home. To cool a room during heat waves and ensure optimal comfort, it’s important to understand the principles of heat transfer.

The interior temperature of your home is influenced by three key elements:

1. Exposure to the sun: Rooms facing south or west will get particularly hot, this is because they are directly heated by sunlight for large parts of the day.
2. Humidity: Rooms that experience high humidity will be more uncomfortable on hot days, while those with lower humidity will be more pleasant to spend time in.
3. Air circulation: Rooms that are full of stagnant air will trap heat, while those with good air circulation will carry the heat away and bring in fresher air.

Heat enters your home through heat transfer. This is the process by which thermal energy moves from one substance, material or system to another.

Here are some examples:

• When you place a saucepan of soup on a hot hob, heat is transferred from the hob to the bottom of the pan and then to the soup, which heats up.
• The fridge in your kitchen transfers heat from its cold interior to the warmer exterior, keeping the food inside cold.
• In your home, heat moves from the air outside to the air inside.

Heat transfer occurs in three main ways:

1. By radiation: the sun heats exterior surfaces that then radiate heat inwards.
2. By conduction: windows and walls conduct outside heat towards the inside.
3. By convection: warm air currents increase the heat in a room, while cool air currents cool a room.

To reduce these types of heat transfer, you must insulate and ventilate your home effectively.

One of the easiest ways to cool a room, without fans or air conditioning, is to optimise its natural ventilation.

Let in cool air by opening windows early in the morning and late in the evening when the air is cooler and keep them closed during the day to keep the heat out. This will help to lower the temperature of your home.

To maximise this cooling effect, open windows that are opposite each other to create a through-flow of air across the room or what is known as cross-ventilation.

If you have roof windows, open them to create an upward draft. This 'chimney effect' allows the accumulated hot air under the ceiling to be drawn out and replaced with fresh outside air, this is known as stack ventilation.

Installing heat protection devices is another great way to keep unwanted heat out of your home. 

If you have VELUX roof windows, consider adding the following heat-protection accessories:

• Anti-heat blackout shutters - these robust aluminium electric roller shutters sit on the outside of your roof windows and help lower indoor air temperature by up to 5°C. They also block out the light at night and act as an insulator in the winter, helping keep your home at an optimum temperature all year round.
• Anti-heat blackout blinds - sitting on the outside of your roof windows and easy to install yourself, these soft and highly durable mesh fabric blinds are solar powered and controlled from inside your room or via your VELUX app. They block out sunlight and can also act as an insulator on colder days.
• Anti-heat blinds - sitting on the outside of your roof windows and manually or remotely operated, these durable mesh fabric blinds protect against the sun’s glare keeping your rooms up to 4°C cooler inside, while still letting in daylight. 

Discover all our heat protection solutions for roof windows on our dedicated page: Blinds and roller shutters - Exterior heat protection.

To keep your home cool all summer long, good insulation is essential. Here’s what to consider:

Poorly insulated walls allow heat to penetrate your home, raising the indoor temperature and making you work harder to keep your rooms cool.

You can improve your wall insulation by adding insulating panels to your interior walls, injecting your walls with spray foam or installing external insulation, which adds a layer of insulation to the facade of your house.

A poorly insulated roof and loft space will make a significant contribution to your home’s interior heat gain in the summer and make it much harder for you to keep your home cool, even with good ventilation. Adding thick insulation to your loft space and under your roof will help lower the temperature in your whole house.

Mineral wool, foam or rigid board insulation are all well suited to roof and loft insulation.

The floor is often overlooked when it comes to insulation, but it also contributes to heat gain in the summer.

By installing insulation under your ground floor or opting for thick carpets, you can make your rooms feel much more comfortable and help to keep their temperature down. Floor insulation also works well for rooms located above an uninsulated basement or garage.

Windows and doors are also sources of heat transfer. By going for double-glazed windows and insulated doors you can help reduce heat transfer and keep your rooms at an optimal temperature.

Placing draught excluder tape or weather strips around your windows and doors will also help keep warm air out and your rooms cool.

Trees and shrubs can be very useful when it comes to maintaining a pleasant indoor room temperature.

Plant trees and shrubs just outside your house where they will shade your windows and reduce the amount of heat entering the house.

Deciduous trees, such as oak, maple or plane, are particularly effective because they provide shade in summer and allow light to pass through in winter. Plant them far enough away from your house for the roots not to cause cracks in your walls, however. 

In addition to providing shade, these trees will improve your air quality and create a more pleasant environment.

Indoor plants not only look lovely, they can also help freshen up your rooms.

Plants release water into the air, which helps cool their surroundings. Aloe vera, ficus and house palm are all particularly good at this.

If they can tolerate lots of sunlight, place your plants near windows to block out some direct sunlight.

Plant walls, or indoor vertical gardens, are another way to freshen up a room.

Plant walls absorb heat and release moisture, which helps lower indoor temperatures.

They will also improve your air quality and add a real wow-factor to your space.

Ferns, pothos and philodendron work particularly well in plant walls, because they grow vertically and require little maintenance. Although you will still have to remember to water them regularly to keep them looking on top form.

If you don't have space to plant trees outside or create a plant wall inside, you could still use potted plants on your patio, balcony or in window boxes to help cool your rooms.

Climbing plants, such as jasmine, can be grown on a trellis in pots and provide shade when placed in front of windows.

Potted plants also have the advantage of being mobile, so you can move them according to the position of the sun.

Electrical appliances, especially large appliances like ovens, tumble driers and dishwashers, can be significant contributors to heat in your home. Limit their use during the hottest part of the day.

If possible, try to cook outside on a barbecue to keep your kitchen cool and use smaller cooking appliances that generate less heat, such as a microwave or air fryer.

Electronic devices, like televisions and coffee machines, use energy and produce heat while on standby too, so switch them off at the socket. 

Incandescent or filament light bulbs produce a lot of heat. To help cool your rooms, replace them with more efficient LED bulbs.

LED bulbs produce less heat and use less energy, so they help keep your home cooler and reduces your energy consumption and bills.

Avoid switching on unnecessary lights during the day too, especially if they are near windows where the sun can heat them more.

Opt for low-energy-consumption appliances, such as fridges, freezers, washing machines and dishwashers, as these will generate the least heat and use less energy, helping to keep your rooms cool and your energy bills down too.

Appliances are rated with an energy efficiency rating ranging from A to G, with A being the most energy efficient and G being the worst. 

Final tip: certain technologies can help you improve the thermal comfort of your home while optimising your energy efficiency. 

Although using dehumidifiers in the summer may seem counterintuitive, these devices actually make the air drier and decrease the feeling of heat.

These work particularly well at cooling basements, bathrooms and utility rooms, which are more prone to humidity.

A smart meter will help you monitor and control your home's energy consumption in real time. Use the data it provides to better understand and manage your energy consumption.

By identifying which devices consume the most, you can adjust your usage to avoid excessive heat production.

VELUX ACTIVE with NETATMO is a connected home system that automatically regulates your home’s ventilation and solar protection to improve your indoor air temperature and air quality.

Easy to install, this system allows you to control VELUX roof windows, blinds and roller shutters to help you cool a room intelligently.

The system uses temperature, humidity and carbon dioxide sensors to automatically adjust your windows and blinds according to interior and exterior conditions.

Controlled mechanical ventilation (CMV) or extraction fan systems are designed to renew your indoor air by balancing incoming and outgoing air flows.

During the summer, a dual-flow extractor fan will allow the incoming air to be filtered and pre-cooled using the heat from the extracted air.

This system allows you to benefit from ventilation without overheating your house, which is particularly useful during heat waves.