The "Shenzhen Building Design Code" officially came into effect in August of this year, adding another city to the list of cities implementing restrictive policies on the use of glass curtain walls. With the release of the new regulations, some building materials companies have seized on the news, claiming that glass curtain walls are nearing their end of life and claiming to have "successfully developed a perfect alternative."

What impact will the increasing number of restrictive policies have on glass companies? As the primary material for building curtain walls, will glass's dominance be replaced by other materials?

Negative news continues

As early as 1910, architectural master Walter Gropius first used glass curtain walls in the new Bauhaus campus. In 1958, another design master, Ludwig Mies, collaborated with Johansson to design the all-glass Seagram Building in New York.

Glass curtain walls offer a simple, luxurious, and modern design, reflecting the surrounding scenery and providing a strong decorative effect. They also combine the wall and window into one, resulting in a lightweight design that is equivalent to 1/12 of a brick wall and 1/10 of a concrete wall. Construction time is significantly shortened, saving two-thirds of the time required for conventional building construction. Consequently, curtain walls have rapidly developed worldwide, becoming a popular style.

Before 1990, glass was the primary material for curtain walls in China. The Great Wall Hotel in Beijing, my country's first curtain wall building, was the first to feature an all-glass curtain wall. Since then, glass curtain walls have rapidly developed as a new architectural style in China.

However, in recent years, negative news regarding glass curtain walls has emerged.

There's a rumor that the optical focus of a curved glass curtain wall building set a car across the street on fire. Others claim that the reflections from the curtain wall kept people awake, leading to legal action. News reports of glass exploding or falling, injuring people, also frequently appear in the media. Such news has raised concerns about glass curtain walls.

As a result, some provinces and cities have introduced policies that restrict the use of glass curtain walls to "ban," "use with caution," or "not suitable" depending on the type of building. The Shenzhen Building Design Code, which officially came into effect in August, explicitly prohibits the use of glass curtain walls in eight types of buildings. These include: residential buildings, hospitals (outpatient clinics, emergency rooms, and wards), primary and secondary school teaching buildings, nurseries, kindergartens, and nursing homes; new construction, renovation, expansion, and facade renovation projects; second-floor or higher floors of buildings adjacent to primary and secondary school teaching buildings, nurseries, kindergartens, and nursing homes; and buildings located at T-junctions facing straight roads.

The regulations also specify that glass curtain walls should be used with caution in the following types of buildings: buildings adjacent to residential buildings, hospitals (outpatient clinics, emergency rooms, and wards), confidential units; buildings within designated historical districts, cultural relics protection areas, and scenic spots; and high-rise or super-high-rise buildings located near mangrove forests and other bird sanctuaries.

The regulations also prohibit the installation of glass curtain walls in the following locations: at urban intersections; within 20 meters of buildings on both sides of urban arterial roads, overpasses, and elevated highways, and within 10 meters of other road sections (measured from the surface). If glass curtain walls are necessary, they should be low-reflective, taking into account the impact on adjacent buildings and the surrounding environment.

The problem is not unsolvable.

The restrictions on glass curtain walls in these provinces and cities suggest that their primary purpose is to protect safety and resident health. However, Liu Jun, an expert member of the National Technical Committee for Standardization of Building Doors, Windows, and Curtain Walls, believes such regulations are a case of "throwing the baby out with the bathwater."

"Light pollution is indeed a growing problem, but by considering the projection position according to different angles, directions, and lighting conditions during curtain wall installation, and applying energy-saving reflective coatings, the problem can be solved." Liu Jun believes that some cities' regulations follow the principle of "better to kill a thousand by mistake than to let one go."

Lin Xiaoliang, Sales Director of Qingdao Hengda Glass Technology Co., Ltd., believes that problems with glass curtain walls, such as light pollution and spontaneous explosion, are ultimately "not the fault of the glass companies," but rather "the incompatibility of the construction companies, the incompetence of the designers, and the incompetence of the owners."

"Light pollution occurs when the client's designers blindly choose high-reflectivity film products in pursuit of visual effect. Only 20% to 30% of the so-called breakage seen by the outside world is actually spontaneous explosion, while much of it is caused by improper design and installation," Lin Xiaoliang explained to reporters.

Liu Jun also believes that there are many reasons for spontaneous explosion, such as inherent material factors, processing techniques such as uneven tempering furnaces, and construction problems. However, these are merely superficial symptoms. The underlying cause lies in the incompatibility of various material properties caused by design concepts, resulting in excessive induced stress and, consequently, spontaneous explosion of tempered glass.

"Without addressing conceptual coordination, these problems will be difficult to resolve," Liu Jun emphasized, emphasizing the importance of the concept of "coordination." "This industry needs more professionals to apply this concept to the doors, windows, and curtain wall industries to reduce the spontaneous explosion rate of glass curtain walls. Why do foreign glass curtain walls rarely have problems? Because they introduced the concept of 'harmony' very early on. Many domestic companies simply imitate them, often reducing specifications due to cost factors, leading to subsequent problems."

Li Hui, Deputy Secretary-General of the China Architectural Glass and Industrial Glass Association, believes that there are solutions to problems like spontaneous explosion and light pollution. For example, the use of ultra-clear glass, laminated glass, and homogenized tempered glass can all prevent spontaneous explosion. Low-e glass has a very low reflectivity and causes virtually no light pollution.

Glass is a Must

After the ban on glass curtain walls was issued, some non-glass companies seized the opportunity to promote their own wood-based panel curtain wall materials, posting online that glass curtain walls are nearing their "end of life." They claimed that their wood-based panels "not only successfully address the safety hazards of glass curtain walls, but also protect against light pollution, explosions, detachment, fire, and water seepage. They also offer a rich variety of colors, a high cost-effectiveness, and far superior earthquake resistance, acid and alkali resistance, and other indicators."

In response to these claims, Li Hui argues that glass's lighting, thermal insulation, and aesthetic qualities are irreplaceable. Glass curtain walls are also an irreplaceable building material for high-rise buildings, and therefore will continue to be used for a long time.

Lin Xiaoliang acknowledges that glass is indeed inferior to many other materials in terms of thermal insulation, energy saving, material strength, and safety. However, humans have been connected to glass for over 5,000 years. Why? Because glass's natural properties, including texture and grain, satisfy human aesthetic and psychological needs in a way that other materials cannot match.

"So what we have to do is to make the non-energy-saving glass relatively energy-efficient. There is no other way because it is irreplaceable. Glass is the least energy-efficient and has various shortcomings, but it is necessary to use it, so we have to find various solutions to make it as energy-efficient and safe as possible." Lin Xiaoliang said.