Solar Control Glass: Can Better Windows Keep Your Home Cooler During a Heatwave?

Solar control glass can help reduce the amount of solar heat entering a home through its windows during hot weather. Standard glazing can be one of the main routes by which a property gains heat in summer: sunlight passes through the glass and warms floors, furniture and internal surfaces, which then release heat into the room. In a well-insulated house, that heat can be slow to escape.

The answer is not simply to buy “better insulated” windows. Summer comfort depends on solar gain, the glass specification, which direction the windows face, how they open and whether you can shade them effectively. The right combination can make a noticeable difference during hot weather.

Why overheating through windows matters more now

The UK has experienced increasingly notable summer heat. The Met Office reported that England had its warmest June on record in 2026, while the UK recorded its second warmest June. A new UK June daily maximum temperature record of 38.0°C was also verified for 26 June 2026.

The Met Office has also highlighted a longer-term trend towards warmer UK summers. That does not mean every summer will be exceptionally hot, but it does make overheating a more important consideration when choosing glazing for south- and west-facing rooms, conservatories and homes with large areas of glass.

What is solar gain?

Solar gain is the heat added to a building by sunlight. Standard clear glazing admits useful daylight, but it also allows a proportion of solar energy to enter. In winter that can be beneficial. In a heatwave, especially on a large west-facing window in the afternoon, it can contribute to uncomfortable internal temperatures.

The aim is not necessarily to block all solar energy. It is to choose a specification that balances daylight, winter performance and summer heat control for the orientation and use of the room.

How solar control glass can reduce overheating

Solar-control glass is designed to reduce the amount of solar heat passing through the glazing. Depending on the product, it may use coatings or tinted glass to reflect or absorb more solar energy than standard clear glass while still allowing useful daylight.

It can be particularly useful for conservatories, large glazed doors, south- and west-facing rooms and modern homes with generous window areas. Cliffside can incorporate solar-control glass within different glazing specifications, so it is worth discussing orientation and room use rather than choosing glass from a brochure alone.

Does double glazing keep heat out in summer?

Double glazing reduces heat transfer between inside and outside, which helps limit heat entering by conduction when the outdoor air is hotter. However, standard double glazing does not automatically stop direct solar radiation. A highly insulated window can still allow significant solar gain through the glass if it is in strong sun.

That is why summer performance should consider both U-value and solar-control characteristics. One measures heat transfer through the window; the other relates to how much solar energy passes through.

Ventilation still matters

Windows also need to help you remove heat when outdoor conditions allow. Opening windows on opposite sides of the home can create cross-ventilation, while secure night ventilation can help purge heat after sunset. Tilt-and-turn or appropriately configured casements can offer flexible opening options, although security and safety always need to be considered.

During the hottest part of the day, opening a window can make a room warmer if the outside air is hotter than the inside. Ventilation is most effective when outdoor temperatures fall below indoor temperatures.

External shading is extremely effective

Stopping sunlight before it reaches the glass is often more effective than trying to deal with the heat once it has entered. External awnings, shutters and carefully designed overhangs can reduce direct solar gain. Trees and other landscape shading can also help, although they need to be planned around daylight and maintenance.

Internal blinds and curtains are still useful, especially reflective or well-fitted products, but the glass has already absorbed or transmitted some heat by the time the sunlight reaches an internal blind.

What about frame material?

Frame choice has less influence on summer overheating than glazing area, orientation and shading, but it still affects overall thermal performance and design. Modern uPVC and thermally broken aluminium systems can both deliver good insulation. Aluminium can create slimmer sightlines, which is attractive on contemporary homes, but a larger glazed area may also admit more solar energy if the glass specification is not chosen with overheating in mind.

Best window approach for hot weather

• Prioritise solar-control glazing on the elevations that receive the strongest sun.
• Use external shading where practical, especially on south- and west-facing glazing.
• Plan secure ventilation so heat can be released in cooler evening and night-time conditions.
• Do not assess windows on U-value alone; ask about solar performance too.
• Consider the whole room, including roof glazing, large doors and conservatory glass.

Choosing heat-reducing windows for a Lincolnshire home

There is no single “heatwave window” that suits every elevation. A north-facing room and a west-facing conservatory have very different solar exposures. Cliffside can help you compare glazing, frame and opening options based on the orientation of your property, the amount of glass and how the rooms are used, including solar-control glass for applications where overheating is a concern.