Glass – in this case architectural glass used as construction material – is most typically found in transparent glazing for building exteriors. Examples of glazing are windows in external walls, glass doors, transparent walls for internal partitions, and glass used as a design feature in architectural works.
The word “glazing” derives from the Middle English word for ‘glass’, and refers to the part of a wall or window that is made of glass. Glazing also describes the work done by a professional glazier. A glazier is a construction professional who selects, cuts, installs, removes and replaces residential, commercial and artistic glass. Glaziers also install aluminum storefront frames and entrances, glass curtain wall framing, shower enclosures, and glass and mirror walls.
Glazing can be mounted into a window sash or door stile, usually made of wood, aluminum or PVC. The most common types of glass used in construction include clear and tinted float glass, tempered glass and laminated glass, as well as a variety of coated glass – all of which can be glazed singly or as double or even triple glazing units. Ordinary clear glass has a slight green hue, but several manufacturers offer special types of clear glass. For glazing buildings, safety glass such as reinforced, toughened or laminated glass is often used. Toughened and laminated glass panes can be bolted directly to a metal frame with bolts passing through drilled holes in the glass pane.
Early types of window glass are hand-blown. Unfortunately, this method was very expensive and could not be used to make large panes. By the end of the 19th century, this was replaced by machine manufactured glass.
Today, the most commonly used types of glass for windows, glass doors, transparent walls and windshields is flat glass – also known as sheet glass or plate glass. This soda-lime glass, so-called for its slight greenish tinge, is produced using the float glass method. Soda-lime glass is divided technically into glass used for windows, called flat glass, and glass for containers, called container glass.
Also called the Pilkington process, the float glass method involves pouring molten glass on a bath of molten metal, typically tin, although lead and various low melting point alloys were also used. The glass floats on the tin and spreads flatly along the bath, lending a smooth surface to both sides. It cools and slowly solidifies as it travels over the molten tin and leaves the bath in a continuous ribbon. The glass is then annealed and cooled in an oven. Sheets of glass produced with this method have uniform thickness and very flat surfaces.
Glass block or glass brick was originally developed in the early 1900s to provide natural light in industrial factories. It is used to delineate areas of privacy but still admit light, such as in underground parking garages, washrooms and public swimming pools.
Laminated glass is manufactured by bonding two or more layers of glass together with layers of PVB to create a single sheet. The PVB interlayer serves as both sound insulation and as a safety feature. Different types of layering produce different results when the glass is broken.
Where safety is a concern, laminated glass is used. Automotive glass for windshields is typically laminated annealed glass. When broken, the PVB layer prevents the glass from shattering, creating instead a “spider web” cracking pattern. Tempered laminated glass, on the other hand, is about 4 to 6 times stronger than annealed glass. It is designed to shatter into small pieces to avoid possible injury. When both types of glass are broken, it produces a “wet blanket” effect and will fall out of its opening.
Toughened or tempered glass is used in commercial structures for unframed assemblies such as frameless doors, shower doors, door lites and vision lites adjacent to doors. It is also used for refrigerator trays, diving masks, as a component of bulletproof glass and various types of plates and cookware. Since 1977, US federal law has required glass located within 18 in (46 cm) of a floor or doorway to be tempered.
When security is a concern, heat strengthened laminated glass is often used. Stronger than annealed, but not as strong as tempered, heat-treated glass has a larger break pattern, but because it holds its shape, it remains in the opening and can withstand more force for a longer period of time, making it much more difficult to get through.
Architectural glass can be coated with a low-emissivity substance for more energy-efficient structures. Coated glass lets visible light pass through, but encourages radiant heat to remain on the same side of the glass from which it originated. The result is that radiant heat originating from indoors is reflected back inside in winter, thus preserving the heat inside the room, while infrared heat radiation from the sun is reflected away during summer, keeping it cooler inside.
Electrically heatable glass is a relatively new product, which has promising applications in designing buildings and vehicles. A low-emissive coating on this type of glass decreases the loss of heat by approximately 30%. Heatable glass can be used in all kinds of standard glazing systems made of wood, plastic, aluminum or steel.
A recent innovation is self-cleaning glass for building, automotive and other technical applications. A nanometer-thin coating of titanium dioxide on the surface of the glass allows ultraviolet rays to catalyze the breakdown of organic compounds on the surface; at the same time, the coating also attracts water, forming a thin sheet that washes away the broken-down organic compounds.
Insulated glazing or double glazing consists of two or more layers of glazing separated by a spacer along the edges and sealed to create a dead air space between the layers. This type of window is designed for maximum thermal insulation and noise reduction. Sometimes the space in between is filled with an inert gas for energy conservation purposes, as in the case of low-energy buildings in sustainable architectural design.
For more answers to your questions regarding glass and glazing, contact Freedom Restoration at 410-451-7110 or click here.