How External Solar Shading Reduces Solar Gain in Commercial Buildings

In today’s climate-conscious built environment, managing heat gain in buildings is no longer just a matter of comfort; it’s an energy efficiency and sustainability imperative. Among the most effective and passive strategies for achieving this is solar shading. When fitted externally to glazing, solar shading systems can significantly reduce solar gain, limit reliance on mechanical cooling and support occupant comfort and wellbeing.

Understanding Solar Gain

Solar gain refers to the increase in temperature in a space as a result of solar radiation. While beneficial during colder months, excessive solar gain during warmer periods leads to overheating, occupant discomfort and increased demand for air conditioning systems.

According to the UK Green Building Council, energy used to cool buildings in the UK is on the rise, with the demand for space cooling projected to increase by 70% by 2050 if mitigation strategies are not adopted. The right shading system can play a pivotal role in reversing this trend.

Why External Shading is Most Effective

While internal blinds are widely used, external shading systems are far more effective in preventing solar radiation from ever reaching the glass surface. This results in substantially lower solar transmittance and cooling loads.

A report by Solar Shading for Low Energy Buildings (IEA SHC Task 25) found that external shading can block up to 90% of solar heat gain, compared to 50-60% with high-performance internal blinds. This difference has significant implications for energy use and internal comfort.

Key Benefits of External Solar Shading

1. Reduced Cooling Demand

External shading reflects a large proportion of solar radiation before it reaches the glazing. According to Professor Heiselberg of Aalborg University, airtight and well-insulated modern buildings are particularly vulnerable to overheating, even outside summer months. Shading systems mitigate this by reducing the load on air conditioning systems.

2. Improved Thermal Comfort

Uncontrolled solar gain creates uneven surface temperatures across glazed areas, causing discomfort from radiant heat. The Zero Carbon Hub reports that up to 20% of England’s housing stock already experiences overheating, a figure expected to rise due to climate change. In commercial buildings, this translates into reduced employee productivity and increased complaints.

3. Support for Passive Design and Net-Zero Goals

Incorporating external shading into building design supports passive cooling strategies and aligns with RIBA 2030 climate targets and UKGBC Net Zero Carbon Buildings Framework. Unlike mechanical systems, solar shading does not consume operational energy.

4. Integration with Smart Systems

Automated shading, integrated with BMS (Building Management Systems), optimises blind positioning based on sunlight intensity, time of day and internal conditions. This approach ensures consistent performance and minimal user intervention, helping buildings like The Shard in London achieve a gtot (total solar energy transmittance) of just 0.12, or 88% heat rejection.

External vs Internal Shading: A Comparative Overview

Feature	External Shading	Internal Shading
Heat Rejection	Up to 90%	50–60%
Aesthetics	Visibly integrated into façade	Often hidden or internal
Performance	Stops heat before it enters	Heat already inside before blocked
Durability	Weather-resistant materials	Protected from weather but less effective
Automation	Highly compatible with smart systems	Also compatible, but less dynamic

The Role of g-value and gtot

g-value is the measure of total solar energy transmittance through a material (e.g., glass). However, in modern solar management, gtot – the combined performance of glazing and shading systems – is a more meaningful indicator.

According to REHVA (Federation of European Heating, Ventilation and Air Conditioning Associations), buildings with external shading can achieve a gtot below 0.15, greatly reducing solar gain without compromising daylight.

Applications in Commercial Buildings

External solar shading is now a feature in many high-performance commercial projects across the UK:

• Office Buildings: Reduces glare and cooling loads, supporting employee wellbeing and BREEAM targets.
• Hospitals and Care Facilities: As highlighted by Lord Krebs and Professor Alan Short, 90% of hospital floor space is at risk of overheating. Shading provides a cost-effective alternative to retrofitting air conditioning.
• Retail Spaces: Preserves interior product quality and improves customer experience by maintaining thermal comfort.
• Education and Public Buildings: Enhances learning environments and reduces public sector energy costs.

Conclusion

In a time of rising temperatures and tighter energy regulations, external solar shading is one of the most effective passive strategies for managing internal comfort, reducing operational energy use and protecting glazing from solar stress.

At Bright A Blind, we specialise in the design, installation and maintenance of high-performance external shading systems for commercial buildings. From automated louvre roofs to fabric tension systems, we help our clients integrate shading seamlessly into architecture.

Speak to our team to explore how we can help you reduce solar gain and future-proof your building.

For more information call 020 7700 6000 or send an enquiry.