Stuart Dantzic, MD of solar shading expert, Caribbean, looks at why managing heat before it enters the building is becoming central to modern home design.

For hundreds of years, energy efficiency in the UK was framed around keeping heat in. In times past, when intense cold and long, dark winters dominated, this made sense. Today’s demands are different, and after the hottest year on record in 2025, many homes are no longer struggling to stay warm. In fact, quite the opposite.

Spend time in a modern home with large areas of glazing and a pattern begins to emerge. Morning light fills the space and it feels comfortable. By mid-afternoon, that same room can feel stuffy and overheated. The temperature rises, the air feels still and the space becomes difficult to use.

This is because sunlight passes through glass with ease, and once inside, it is absorbed by surfaces such as floors, walls and furniture, which then release that energy as heat. Unlike the sunlight that entered, that heat does not escape easily and builds up over time.

My company, Caribbean, is one of the UK’s leading manufacturers and suppliers of solar shading solutions, from pergolas and awnings to external blinds. Last year, we commissioned a White Paper on the implications for householders of warmer summers and how the sun affects temperature control.

Research from the White Paper shows that more than half of homeowners recognise direct sunlight as the main cause of overheating. Only a small proportion connect this with the role of window shading. That gap helps explain why many households still rely on reactive measures that offer limited relief.

Drawing curtains or lowering internal blinds can darken a room, and fans can move warm air around, but neither approach addresses the source of the problem. By the time they are used, the heat is already inside. If the aim is to maintain a comfortable indoor temperature, the focus needs to shift to stopping that heat before it enters.

Positioned outside the building, external blinds block sunlight before it reaches the glazing. This has a direct and measurable effect on internal conditions. Research referenced in the Caribbean study shows that well-designed external systems can block up to 97% of solar heat, with temperature reductions of up to 19.5°C recorded in controlled settings. That level of control turns rooms that would otherwise be avoided into places that remain comfortable throughout the day.

A large part of the challenge is that the sun does not behave in a fixed way. Its position shifts throughout the day and its intensity changes across the year, so the conditions a building faces are always moving.

Managing that effectively means the response must move with it. Shading needs to sit outside the glass, where it can deal with solar gain before it enters, and it needs to respond as light levels and temperatures change to maintain a comfortable internal environment. Systems that can adjust in real time, whether through sensors or simple automation, are able to keep conditions more stable without constant input.

Overheating is not evenly distributed across a home. Bedrooms tend to be the most affected, often because excess heat disrupts sleep, while living spaces follow closely behind, especially in open-plan layouts with large glazed doors. External blinds can be specified to suit each part of the building, taking into account orientation, glazing type and how the space is used, rather than applying a single solution across every elevation.

Large glazed areas remain central to modern residential design. They bring in daylight, open up views and create a strong connection to the outside. They also increase exposure to solar gain. External shading allows these features to remain while managing their impact, so the building retains its openness without compromising comfort.

Many households still rely on measures such as air conditioning, fans or closed curtains. These may offer short-term relief, but they do not deal with the root cause. External blinds form part of that response. By managing solar gain at source and adapting to changing conditions, they help maintain more stable indoor temperatures and reduce reliance on energy-intensive cooling.