What is Spandrel Glass?
Spandrel glass is an architectural material used to cover construction materials, disguise things like arches and columns, and present a finished, seamless, and sleek exterior to buildings. It tends to be very durable but is aesthetically pleasing in most cases, too. Architects and designers sometimes use it for specific features, particularly cascading glass “curtains,” but it can also be used to cover entire structures. Most buildings that look from the outside like they’re made entirely out of glass are covered in this material.
The word “spandrel” is an architectural term that refers to an archway or other crested system of supports. Spandrel glass is one of the only types of glass capable of covering this type of structure in a way that not only fits its curvature, but also creates the illusion of a single and unbroken wall. Some archways are intentional and used as passageways, but others are designed for structural support and load bearing. Covering these with glass can often create a more pleasing, polished look than would filling them in or building a more traditional wall over them.
This type of glass tends to be opaque, and is usually reflective. Sometimes people can see out of it, but in most cases it actually repels light and often appears to have a mirrored surface. When the glass is intended for the outside of a building it is usually heat-treated and insulated so that it functions more like a wall than a simple pane.
One of the most valued aspects of this material is its ability to create an overall uniform appearance. The glass is often colored, and as such it can match most other types of glass that are used to create a building front. Green and blue hues tend to be some of the most common, as these are able to reflect the sky with particular precision. Bronze, silver, and metal-flecked panels can also be used, either for an entire project or to accent or highlight certain areas.
When panels have been fused together properly, it can be difficult to see where one section of a building begins and ends. Some designers also integrate regular windowpanes in with spandrel sections, and the material can be used for internal features and coverings, too. It’s particularly good at covering unsightly interior building materials and fixtures like beams, pipes, and water and air pumps. In these instances the glass often looks purely artistic, though it often has a structural role, too, particularly when it’s used as part of a wall or incorporates things like sound and temperature insulation.
Spandrel glass is typically created using a heat intensive process known as “fired-on frit.” This process includes a ceramic frit — a material used as a basis for glassmaking — that is fused to the glass by bringing it almost to the point of melting. When warm, the glass will also bend and twist relatively easily, which means that craftsmen can shape it to an architect or contractor’s specifications. The resulting product will not usually fade or warp over time, and most panels are guaranteed for life.
The firing process may also help strengthen the glass, making it particularly suited for industrial uses. In addition, spandrel is up to five times stronger than annealed, or traditional, glass. In fact, many modern buildings incorporate the use of spandrel if a smooth appearance is desired.
Thermal Heat Benefits
It is also particularly resistant to thermal conditions. As such, in addition to attributing to the uniform appearance of a building, it can also be used to supply specific areas of a building with heat thanks to its excellent thermal capabilities. Various industrial buildings have been lined with spandrel glass on the inside as well as the outside in order to trap and maintain solar heat, which can reduce energy costs and promote “green” environmental practices. The startup costs can be high, but the savings over the long term can be substantial.
You cannot see through spandrel glass from the outside, whereas you can see through vision glass from outside. Spandrel glass, from a heat gain standpoint, can pretty much be considered opaque. It hardly lets any light in and is very good for stopping the suns radiation. Vision glass lets a lot more heat in, and a film or tint on the glass helps reduce heat gain.
@ Aplenty- I would just like to point out the difference between spandrel glass and the glazed glass on a building. Spandrel glass is designed to hide the structure, so it is created to be only opaque enough to give the glass depth and dimension. The glazed glass that covers the windows is meant to be translucent. The coatings are designed to let light in, but control heat transfer, brightness, and condensation.
@ Aplenty- You are right about what spandrel glass is. Architects use spandrel glass to create the flowing glass curtains that wrap around some structures.
A perfect example of a building cloaked in spandrel glass and tinted double insulated glass would be the Mandalay Bay Casino in Las Vegas. The entire hotel is covered in insulating glass coated with an optically thin 24K gold film. Do not quote me on this, but I am pretty sure that the spandrel glass is flecked with 24K gold as well to match the insulating glass. There are also vertical stone columns that run up three quarters of the building to hide some of the structural components.
The purpose of the gold tint is to insulate the building from IR radiation, and to reflect the bright desert sunshine. These features both keep the building cool, and reduce interior glare. The coating is also aesthetically pleasing, creating a view of the strip that is bathed in gold when seen from the inside.
So if I understand the article correctly, then spandrel glass is the glass that architects use to conceal the framework of a glass building. Is this structural glass different from the glass that creates the reflective facades of glass buildings and skyscrapers? How exactly are they different? Does the tint on the glass serve a specific purpose, or is it purely aesthetic?
I live in Phoenix, and many of the buildings have copper, green, blue, and silver reflective glass covering their exterior. Do designers install the reflective glass to reflect sunlight or protect against the heat? The buildings are nice to look at, but I am just wondering if there is another reason besides looks.
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