Can Internal Blinds Stop Overheating?

Solar shading has been identified in multiple recent reports as one of the most effective ways to reduce overheating risk in UK homes during heatwaves, with the UK’s housing stock increasingly vulnerable to higher summer temperatures.

The Government’s Climate Change Committee, alongside research from Loughborough University and the University of East London, has called for greater use of passive measures such as solar shading to protect homes from overheating and the associated risks to health and wellbeing

How effective are internal blinds as temperatures rise?

Internal blinds have traditionally been used in the UK to manage glare, improve privacy and help retain heat during colder months. However, as summer temperatures rise, their effectiveness at preventing overheating is limited.

This is because, with internal blinds, solar radiation still passes through the glazing, allowing the glass to heat up and release warmth into the room before the blinds can significantly reduce the heat build-up.

What the research says: internal vs external blinds

A British Blind and Shutter Association (BBSA) study, carried out in a London flat, directly compared three scenarios:

• An unshaded window

• The same window fitted with internal blinds

• The same window fitted with external blinds

The results showed that while internal blinds provided some reduction in peak temperatures, external blinds delivered a 40% reduction in internal heat build-up, significantly limiting overheating during hot weather. The unshaded window experienced the highest internal temperatures by a wide margin.

This study clearly demonstrates that internal blinds alone cannot prevent overheating, because the heat has already entered the building.

The type of internal blind still matters

Not all internal blinds perform in the same way. Internal blinds can help to moderate indoor temperatures, particularly when the window-facing side has a reflective finish and lighter-coloured, thicker fabrics are used.

They remain highly effective for reducing glare on screens and work surfaces, improving visual comfort, providing privacy, and supporting more comfortable internal environments.

Internal blinds can help reduce heat loss in winter

Internal blinds continue to play an important role in winter performance. Research by the University of Salford found that internal blinds and shutters can reduce heat loss through windows by between 13% and 33%, depending on the system used.

The BBSA has also demonstrated that:

• Screen roller blinds can reduce heating energy use by around 23%

• Venetian blinds can reduce heating demand by around 10%

Why external blinds are the solar shading of choice

External blinds are widely recognised as the most effective form of solar shading for preventing overheating, because they stop sunlight before it reaches the glass.

UK Parliamentary written evidence on overheating confirms that external solar shading is significantly more effective than internal shading, with certain systems capable of stopping the vast majority of solar gain at the façade.

As a result, architects increasingly integrate external blinds into building designs to protect south- and west-facing glazing and reduce overheating risk.

Designed for performance and everyday living

External blinds typically feature durable aluminium frames and tough, weather-resistant fibreglass fabrics. Their open-weave construction allows occupants to maintain outward visibility even when the blinds are lowered, while still significantly reducing solar gain.

They can be fitted to a wide range of window and door types, including large glazed areas and rooflights.

Smart temperature control

External blinds can be automated using sensors that respond to sunlight or internal temperatures, raising and lowering the blinds to help maintain comfortable indoor conditions throughout the day.

They can also be controlled manually via wall switches or smartphone apps, giving occupants precise control over light, heat and privacy with minimal energy use.

Talk to the experts

Kensington Blinds has over 40 years’ experience designing and installing shading solutions for homes and a wide range of commercial sectors.

If you’d like to discuss your project or understand which shading solution is right for your property, our team is always happy to help.