Managing Reflection in Glazing
Glazing plays a pivotal role in the performance, aesthetics, and functionality of modern buildings. One critical aspect is the management of reflection in architectural glass. Whether for residential, commercial, or civic applications, reducing unwanted glare while enhancing visibility and comfort is a sophisticated challenge. In this blog, we explore how thoughtful glass selection can support effective reflection control.
Understanding Reflection in Glazing
Reflection in glazing occurs when light bounces off the smooth surfaces of glass instead of transmitting through it. This phenomenon can be both functional and problematic. Reflection occurs across the whole light spectrum, which not only encompasses the bands of visible light but extends into the infrared longer wave spectrum, which whilst we can’t necessarily see it, it contains much of the heat load from the sun.
Measurement
The performance characteristics of all glass types, and combinations used, will include percentage measurements for visible light transmission (VLT), outside reflection and internal reflectance. Solar energy is calculated separately in transmission and reflection to capture levels of infrared behaviour as it interacts with the glazed panel.
Positive Reflection
- Daytime Privacy – Reflective coatings can provide a degree of privacy by limiting outward visibility into a space while maintaining clear views from inside. This effect is due to relative light ratios: with higher exterior brightness during the day, it becomes difficult to see in, but after sunset the balance reverses, making interiors more visible. A more extreme version of this principle is seen in observation mirror products, which use very high reflectivity to prevent any view through the glass.
- Solar Control – In the infrared spectrum, heat-carrying radiation can be selectively reflected or absorbed by the glazing. This reduces the amount of solar heat entering the building, helping to maintain cooler interior temperatures. In warm climates, effective solar control improves energy efficiency by lowering internal heat loads and reducing reliance on mechanical cooling.
Negative Reflection
- Glare and Visual Discomfort – Excessive reflection can create glare, leading to discomfort for both occupants and the surrounding environment. In urban settings, local planning regulations often restrict external reflectivity to less than 20%.
- Residential Perception – Reflective glass is strongly associated with commercial facades, and its use in residential applications is often considered undesirable.
- Reduced Natural Light – Higher visual reflectivity results in lower light transmission, meaning interior spaces receive less natural daylight.
- Balancing Performance – Effective reflection management requires a careful balance between visibility, thermal performance, and design intent.
Techniques for Managing Visible Light Reflection (VLR)
Tinted Glass
Tinted glass has a higher level of absorption compared to clear glass. As a result, more absorbent colours, such as grey and, to a lesser extent, bronze, naturally exhibit lower levels of visible reflectivity.
For comparison, standard uncoated clear glass has an external reflectivity of around 8%. Replacing this with a grey substrate immediately reduces reflectivity to about 5% or less.
This effect also carries through to laminated products, where grey interlayers achieve similar reductions in visible reflection. By absorbing and redistributing light, tints help minimise sharp glare and enhance indoor comfort.
Insulated Glass Units (IGUs)
In insulated glass units (IGUs), the use of multiple panes effectively doubles the reflective surfaces through which light interacts. The natural outcome is an increase in overall reflectivity.
For example, a standard clear glass single pane has an external reflectance of about 8%. When incorporated into a double glazed unit, this rises to around 15%. However, substituting the outer pane with grey glass reduces reflectance back down to approximately 7%.
This is one reason why grey glass is commonly specified in colder IGU climates, such as Tasmania and New Zealand, where higher levels of tinted glass use are typical.
Low E (Low Emissivity) Coatings
Low E coatings are primarily designed to improve energy efficiency by reflecting infrared radiation, helping to manage heat transfer through the glass. From a visual perspective, they also contribute to reducing external reflectance. For instance, single silver soft coat Low E products such as LightBridge™ and Viridian ClimaTech™ typically lower external reflectance by around 2–3%.
Anti-reflective (AR) Coatings
Specialised pyrolytic hard coatings can reduce external visible reflectivity to as low as 1.3–3%. To achieve this performance, the coatings are typically applied to both outer surfaces of the glass (exterior and interior).
AR coatings are more commonly used in European and North American markets, particularly in applications where ultra-clear visibility is essential – such as museum displays, premium retail shopfronts, and high-end showrooms.
Acid-Etching and Surface Treatments
Controlled acid etching creates a frosted or matte glass surface that disrupts light transmission and significantly reduces visible reflections. Beyond lowering glare, these treatments diffuse light to create a softer, more uniform appearance. They are especially effective in decorative applications and in areas where enhanced privacy and visual comfort are desired.
Glass Orientation and Positioning
The way glass is positioned within a building has a significant influence on perceived reflectivity. Both the angle of installation and the orientation of the façade determine how and when sunlight is reflected into the surrounding environment. For example, façades facing direct sun during peak hours are more likely to cause glare unless properly shaded or treated.
Final Thoughts
Reflection in glazing is more than an aesthetic consideration; it directly influences comfort, building performance, and even environmental impact. By combining advanced coatings, thoughtful design, and precision processing, the glass industry continues to refine how we harness and control light.
Whether you are an architect, builder, or homeowner, understanding the role of reflection can help transform glazing decisions from functional necessities into opportunities for exceptional design outcomes.