Keeping your house cool in summer: a complete guide

When temperatures rise outside, your home can quickly heat up if your insulation isn’t up to scratch. Good insulation should reduce the movement of heat into your property, helping your rooms stay cooler during summer while improving energy efficiency all year round. 

Lots of people think that loft insulation is only a winter upgrade, but it actually works just as hard during the summer months. 

In winter, the Sustainable Energy Authority of Ireland (SEAI) estimate estimates that around a quarter of a home's heat can escape through an uninsulated roof. And during summer, that same roof allows heat to enter your home in upper floors and loft spaces. 

Adding loft insulation helps slow down this heat transfer and can make a noticeable difference to comfort levels during hot weather. 

Roof insulation materials can use: 

• Mineral wool 
• Sheep's wool 
• Fibreglass 
• Rigid insulation boards 
• Polystyrene panels 

For most homeowners, it’s a yes. Loft insulation is one of the most effective ways to reduce heat loss in winter and keep rooms cooler in summer. The cost of it depends on the size of your home and materials you choose, but we think it’s one of the most cost-effective energy improvements you can make.

If you're thinking about DIY loft insulation, we recommend checking whether your loft needs ventilation gaps or specialist installation before starting work.

Walls play a major role in regulating indoor temperatures. Homes built after the 1920s often have cavity walls, where two layers of brick are separated by a small gap. Filling this cavity with insulating material can help reduce heat transfer throughout the year.

For older homes without cavity walls, you can insulate cavity and non-cavity walls by fixing insulating panels to the internal or external side of the wall.

Older windows can allow lots of heat into your home during warmer months, making it much harder to keep it cool. Replacing ageing or poorly sealed windows with modern, energy-efficient alternatives can significantly improve indoor comfort.

If you have rooms in your loft, consider replacing your old roof windows with the latest energy-efficient model. This will reduce the heat coming in from outside and improve the ventilation in your loft space, making it feel fresher.

Modern glazing technologies help reduce solar heat gain while maintaining comfortable indoor temperatures. 

For loft spaces and upper floors, upgrading older roof windows can really pay off. Combined with anti-heat blinds or blackout shutters, modern roof windows can help reduce indoor temperatures by up to 5°C, depending on the products used.

There are plenty of ways to reduce indoor temperatures naturally, so give these five steps a go.

Cross ventilation is one of the simplest and most effective ways to cool your home.

Opening windows on opposite sides of the building, such as in your kitchen and living room, creates a through-draft that pulls warm air out while drawing cooler air in, and ultimately stops heat getting trapped indoors. 

This works particularly well during evenings and overnight when outside temperatures are at their lowest.

You probably already know that hot air rises, and the stack effect uses this principle to improve airflow throughout your home.

Opening windows at different heights creates vertical ventilation that helps warm air escape through the highest point of the building while drawing cooler air in from below. For example, opening a downstairs window alongside an upstairs roof window.

Like the last step, this one is most effective during cooler parts of the day and overnight.

We’ve found that preventing heat entering your property is easier than trying to remove it later.

Heat protection accessories such as external blinds and shutters stop the sun's rays before they reach the glass, helping your rooms stay cooler throughout the day.

If you have roof windows, you could try any of the options below:

• Anti-heat blackout shutters can reduce indoor temperatures by up to 5°C while also darkening bedrooms and protecting against harsh weather.
• Anti-heat blackout blinds combine heat reduction with room darkening and improved insulation.
• Anti-heat blinds reduce heat and glare while still allowing daylight into your home, making them ideal for living rooms and home offices.

These can all be automated using VELUX ACTIVE with NETATMO which adjusts blinds and shutters based on indoor temperature, humidity and CO₂ levels, keeping your home cool with minimal effort. 

Blackout blinds can help reduce heat gain by limiting direct sunlight entering a room, but not all blackout blinds are the same. While all blackout blinds reduce light, some are also designed to reflect heat and help keep rooms cooler. If you want to stop heat before it reaches your windows, though, external blinds and shutters would be a better option.

Reflective insulation products are great at reducing heat transfer through your roof during summer.

Typical roof insulation materials include:

• Mineral wool: affordable, effective and suitable for most loft spaces.
• Rigid PIR boards: excellent thermal performance without being bulky.
• Reflective foil insulation: designed specifically to reflect heat away from your property.
• Natural sheep's wool: breathable and environmentally friendly.
• Reflective roof coating: sometimes used on flat roofs to reduce solar heat absorption.

The best roof insulation materials depend on your roof type, available space and whether your main priority is summer cooling, winter warmth or both. Read our complete guide for internal roof insulation. 

Most Irish homes don't have air conditioning, but extractor fans can play an important role.

Extractor fans remove warm, humid air from kitchens and bathrooms while encouraging fresh air to circulate through the rest of your home. They're particularly useful after cooking, showering or using appliances that generate heat indoors. Again, not all of them are made equal – so it’s worth looking at different types and finding the option that’s best for you.

Appliances in your home can create more heat than you might realise.

Light bulbs, televisions, chargers and appliances all play a part in rising indoor temperatures during hot weather. Switching them off completely rather than leaving them on standby can help reduce this background heat gain.

Replacing older incandescent bulbs with LEDs can help, too, as they generate significantly less heat while using less energy overall.

Keeping your house cool in summer isn't just about insulation and ventilation. From when you cook dinner to the sheets you sleep in, a few simple adjustments can help you stay comfortable during even the hottest weather.

Your oven, washing machine and tumble dryer all generate heat – and on already hot days, every little bit adds up.

Try using heat-producing appliances during the cooler parts of the day such as early morning. Cooking with a microwave, slow cooker or air fryer can also help reduce heat build-up indoors compared to a conventional oven.

You could even swap the tumble dryer for an outdoor washing line or airer on warmer days. Your house – and energy bills – will thank you for it.

Loose-fitting, breathable fabrics allow air to circulate more freely and help your body temperature regulate during hot weather. Some of the best options include: 

• Cotton: breathable, absorbent and ideal for everyday wear. 
• Linen: one of the coolest fabrics you can wear thanks to its excellent airflow. 
• Rayon: lightweight and breathable with similar properties to cotton. 
• Bamboo: naturally breathable, soft and moisture-wicking.

Plants do much more than brighten up your home and garden.

Trees and shrubs planted outside can provide valuable shade during hot weather while helping cool the surrounding air naturally. Deciduous trees are popular in Ireland because they provide shelter from the summer sun while allowing light through during the winter months.

Indoors, house plants can contribute to a fresher-feeling environment while improving air quality, too. Some good options include:

• Ficus Benjamina: acts as a filter unit for air toxins.
• Sansevieria: great at purifying the air and low maintenance.
• Dracaena: helps eliminate formaldehyde and other common toxins found indoors.
• Aloe Vera: another easy-to-care for plant that has great air purifying properties.
• Areca palm: excellent for humidifying the air and creating a fresh atmosphere. 

Keeping your home cool in summer is about combining practical solutions that work together – from improving insulation and ventilation to reducing heat gain with effective shading. 

Whether you're making small seasonal adjustments or planning bigger home improvements, every step can help create an indoor environment you’ll love during all weather. 

Looking for more ways to improve your home's comfort and energy efficiency? Explore our guides on what to do about heat in the loft and the benefits of internal roof insulation for expert advice and inspiration.