Low-emissivity glass is revolutionizing building efficiency. Here's how

For centuries, glass has been an integral part of human history, evolving into a key element in modern architecture, available in various forms. It is attractive for its aesthetic appeal, transparency, and ability to transmit natural light. Beautifully described by Jean-Jacques Rousseau as the “most innocent of stones”, glass was primarily used in windows.

However, the sustainability of glass as a building material has gained wider attention in recent years, paralleling the growing demand for environmentally friendly construction practices. Innovative technologies have empowered architects to craft not only unconventional shapes but also sustainable products with this versatile material. In this article, we examine the sustainability of glass, evaluating its impact on the environment, energy efficiency, and resource consumption.

When we think of innovation, we think of advanced technology, robots that are thought to replace humans, or space science. Rarely, do we consider skyscrapers as hub of innovation. Nevertheless, the building industry is undergoing a revolution, one that is set to transform the way we think about construction and energy efficiency. At the centre of this revolution lies glass.

Currently, the ratio of glass to other building materials may surprise you. In modern skyscrapers, glass usage is more than 50% of the exterior surface area. Advances in technology have given glass many new properties, changing how it looks and what it can do. Glass is now more than just see-through; it can also be translucent, reflective, and even produce and protect energy. And transparency isn't just about glass anymore.

Flat glass, commonly used in skyscrapers, has its disadvantages. It easily transfers heat from the inside to the outside because it conducts heat quickly. This can lead to higher energy consumption for heating and cooling. Also, its high light transmittance can result in too much sunlight inside and temperature swings.

When the energy crisis of the 1970s emerged, European governments began to pursue policies to regulate energy consumption. The Ministry of Energy determined that approximately 25% of residential heating costs are a direct result of energy loss from buildings' windows. For this reason, it began funding research studies that could reduce the amount of energy leaking from buildings. In the 1970s, multi-pane windows reached the market and manufacturers began marketing energy-efficient windows for the first time.

Double glazed windows and doors have proven to be an effective solution as they significantly reduce heat transfer through the windows, minimizing the need for excessive heating or air conditioning. Low-emissivity (Low-e) windows also appeared in the 1970s. The first low-e coatings were made using thin layers of gold, creating a green hue. In 1981, the first colorless low-e coatings were produced using silver layers.

Low-e glass was developed to solve these problems. Soft coatings, including Low-e glass, constitute 65% of the total coated market. Soft coated glass with a market value is approximately $28 million in 2022. The forecast for 2023-2028 predicts a compound annual growth rate of 9.23%, propelling the market value to an estimated $47 million by 2028, according to Global Coated Glass Market Research Report, Analysis and Forecast till 2028. The silver material in the nanometer scale found in low-e coated glasses is coated among other materials that provide various anti-reflective properties.

In this way, selectivity is achieved in the electromagnetic spectrum and allows daylight to enter the interior of the building. Low-e coated glasses on this nanometric scale have properties that protect the interior from the harmful effects of sunlight due to their infrared and ultraviolet reflective properties. With these optical properties low-e coated glass makes us feel more spacious in buildings.

Low-e glass is also widely used in buildings in their temperable versions, which enables them to provide solutions for different needs of buildings. In addition to its thermal insulation feature, Low-e glass with tempered properties also provide safety in buildings. It provides security features when laminated. As a result, low-e glasses significantly decreases energy consumption in the building, enhance indoor comfort, and create a healthier environment for building occupants.

Furthermore, their positive impact on energy consumption and long lifetime help to reduce the carbon footprint. Depending on energy efficiency regulations in developed and developing countries, the use of coated double or triple glass in new buildings becomes mandatory. At the same time, the global trend in increasing urbanization and increasing infrastructure projects plays an important role for the coated glass market.

The increasing demand for smart solutions in today's buildings is driving the adoption of smart glass, making it a major trend in the coated glass market. In parallel, key trends are shaping the market's future. Advancements in smart glass technologies, innovations in coating technologies, and a growing industry-wide dedication to sustainability are all contributing factors to the evolution of the coated market.

We can reduce the 5.7 W/m2K U value in single glass to 0.5 W/m2K with triple Low-e coated insulating glass. This means that we provide approximately 10 times more thermal insulation. Solar Low-e product group provides both heat and solar control at the same time with a single coating. Thanks to its coating that prevents the heat inside from escaping, it provides 50% better insulation than standard double glass and also has solar control properties. In this way, it contributes to reducing the heating and cooling loads of buildings.

There is a special project in Ankara, Türkiye, which meets all its heating, cooling and electrical energy needs with solar panels. Thanks to the triple-glazed insulating glass unit, that were used in the project, 81% thermal insulation and 57% more effective daylight control was achieved compared to the uncoated double-glazed insulating glass unit. The investment, made for the solar energy system, pays off in two-three years.

Despite the contribution of the use of Low-e glass in the building industry to reducing the carbon footprint, there are still concerns about the sustainability of glass production, such as high energy consumption and use of natural resources. The use of fossil fuels contributes to greenhouse gas emissions and climate change. Additionally, the extraction and processing of raw materials required for glass production can damage natural ecosystems, especially because of activities such as sand mining.

For these reasons, glass production is often not sustainable. However, the glass industry can reduce these impacts by adopting more sustainable solutions. For example, it can reduce the environmental impacts of glass production by increasing the use of recycled glass, improving energy efficiency, and switching to renewable energy sources.

As a result of Şişecam studies to identify the best practices in regard to energy efficiency, the recovery of lost energy and the reduction of energy needs, we have been able to reduce specific energy consumption by 12% in glass manufacturing over the last 15 years. We aim to expand renewable energy use at its plants eight-fold by 2030.

When evaluating sustainability, it is crucial to consider the entire lifecycle of glass, including its production, use, and disposal. This holistic approach allows informed decisions about using glass in buildings and promotes sustainable construction practices.

We have a responsibility to leave a healthy and sustainable world for future generations. Companies need to act on this responsibility. By implementing well-defined strategies focused on environmental protection, social responsibility, and positive societal impact, we can strive to create a sustainable future. I invite the glass industry to lead this journey toward a more sustainable future.