If your flat turns into an oven every summer, you’re not alone. Across London and the UK, many flats become uncomfortably hot during warmer months, especially during heatwaves. 

The frustrating part is that even with windows open and fans running, the heat often just lingers.

So, why is your flat so hot in summer? And more importantly, what can you actually do about it — especially if you’re renting and can’t make permanent changes?

This guide breaks down the most common causes and gives you practical, effective ways to cool down a room.

Direct Sunlight Is Heating Your Flat All Day

One of the biggest reasons flats overheat is direct sunlight. South-facing and west-facing properties absorb heat throughout the day, especially if you have large windows or skylights.

Top-floor flats are particularly affected, as heat rises and gets trapped in the upper levels of a building.

What you can do:

• Keep blinds or curtains closed during peak sun hours (late morning to early evening)
• Use blackout curtains or reflective blinds to reduce heat gain
• Open windows only when the outside temperature drops

It might feel counterintuitive, but keeping windows shut during the hottest part of the day can actually help keep heat out.

Heat Gets In, But Can’t Get Out

Many flats suffer from poor airflow, especially if windows are only on one side of the property. Without proper ventilation, warm air gets trapped inside and has nowhere to escape.

This is why your flat can still feel hot even late at night.

What you can do:

• Open windows early in the morning and late in the evening when it’s cooler outside
• Create cross-ventilation where possible by opening doors between rooms
• Keep internal doors open to encourage airflow

Even small improvements in airflow can make a noticeable difference.

Everyday Living Adds More Heat Than You Think

You might not realise it, but daily activities can significantly increase indoor temperatures.

Common culprits include:

• Cooking (especially using the oven)
• Showering and hot water use
• Drying clothes indoors
• Electronics like laptops, TVs, and gaming equipment
• Multiple people in a compact space

What you can do:

• Avoid using the oven during the hottest part of the day
• Dry clothes outside or in a well-ventilated room
• Turn off electronics when not in use
• Vent kitchens and bathrooms after use

Reducing internal heat sources can help prevent your flat from overheating further.

Your Flat Wasn’t Designed for Summer Cooling

Many UK properties, particularly older flats and conversions, were built to retain heat, not release it. While this is great in winter, it can cause problems in summer.

Loft conversions and poorly insulated buildings are especially prone to overheating, and unfortunately, these are often the types of properties renters live in.

What you can do:

Since structural upgrades like insulation or new glazing aren’t usually an option, the focus needs to be on temporary, non-invasive solutions that work with your space rather than altering it.

So, How Do You Actually Cool a Flat Down?

There are several simple steps that can help:

What works:

• Keeping blinds closed during the day
• Ventilating at the right times
• Reducing heat from cooking and appliances
• Using fans to circulate air

What doesn’t work (on its own):

Fans can make you feel cooler, but they don’t actually lower the temperature of the room. They simply move warm air around.

If your flat is consistently overheating, you’ll likely need a more effective solution.

The Most Effective Non-Permanent Solution: Portable Air Conditioning

If you’re wondering how to cool a room without making permanent changes, portable air conditioning is the most effective option.

Unlike fans, portable air conditioners actively remove heat from the room, lowering the temperature and improving overall comfort.

Why it works:

• Cools the air rather than just circulating it
• Provides fast, noticeable results
• Doesn’t require installation or structural changes
• Ideal for renters and temporary use

Portable units are particularly effective in:

• Bedrooms (for better sleep)
• Living rooms
• Home offices
• Top-floor flats that trap heat

Why Hiring Makes More Sense in the UK

In the UK, hot weather tends to come in short bursts rather than lasting all year. That’s why many people choose portable air conditioner hire instead of buying.

Hiring allows you to:

• Get immediate relief during heatwaves
• Avoid the upfront cost of purchasing a unit
• Skip storage and maintenance
• Choose the right unit for your space

At Chilly Pepper Hire, we provide flexible, reliable portable air conditioner hire across London, helping you stay comfortable without long-term commitment.

Stay Cool Without Major Changes

If your flat feels unbearably hot every summer, it’s not just you, it’s often the way the building is designed. But while you might not be able to change the structure, you can absolutely improve your comfort.

By managing sunlight, improving airflow, reducing internal heat, and using the right cooling solution, you can make a huge difference.

And when simple fixes aren’t enough, portable air conditioner hire offers a fast, effective way to take control of your indoor temperature.

Struggling with a hot flat? Get in touch with Chilly Pepper Hire today for portable air conditioning hire, one of the best ways to cool down a room fast.