Types of Glass in Buildings: How Each Is Made and Used

Almost every building uses several types of glass, often without the owner knowing which is which. The pane in a bedroom window, the shower screen, the balcony barrier and the glazed roof over a porch may look similar, yet they are made differently, break differently and are required in different places. Choosing the wrong one can mean a pane that shatters into dangerous shards, a barrier that falls out when broken, or a room that overheats.

This guide sorts building glass into three groups: the base glass and how it is made, the processes that make it safer or stronger, and the coatings and assemblies that control heat, light and sound. It is intended as a map; our companion articles go deeper into tempered glass and the comparison of annealed, tempered and laminated glass.

How flat glass is made: float glass

Nearly all flat glass in modern buildings starts as float glass. Raw materials, chiefly silica sand, soda ash, limestone and dolomite, together with recycled cullet, are melted in a furnace. The molten glass is poured onto a bath of molten tin, where it spreads and floats, forming a ribbon with flat, parallel surfaces. The float process was developed by Pilkington in the United Kingdom in the 1950s and has since become the standard method worldwide, replacing older drawn and polished plate glass.

The ribbon then passes through a long cooling tunnel called a lehr, where its temperature is lowered slowly and under control. This is annealing: it relieves the internal stresses that would otherwise make the glass unstable. The result, annealed float glass, is the base material for almost every other product described here. It can be cut, drilled and edged easily. Its weakness is the way it breaks, into large, sharp, dagger-like pieces, which is why it is restricted in locations where people may impact it.

Safety and strength processes

Heat-strengthened glass

Annealed glass is reheated and then cooled with air more gently than in full toughening. This builds a moderate compressive stress into the surfaces, roughly doubling the strength compared with annealed glass. When it breaks, it forms larger pieces than toughened glass, which tend to stay in the frame. It is commonly used in laminated assemblies and in facades where thermal stress is a concern.

Toughened (tempered) glass

Here the glass is heated to around 600 to 650 degrees Celsius and quenched rapidly with air jets. The surfaces cool and set first, then are pulled into high compression as the core cools and contracts. The result is commonly about four to five times stronger in bending than annealed glass of the same thickness, and when it fails it breaks into small, relatively blunt fragments. It cannot be cut or drilled after processing, and it carries a small risk of spontaneous breakage from nickel sulphide inclusions, which heat-soak testing reduces.

Laminated glass

Two or more panes are bonded with a polymer interlayer, most often polyvinyl butyral (PVB) or a stiffer ionoplast, under heat and pressure in an autoclave. If the glass breaks, the fragments stay bonded to the interlayer, so the pane cracks but tends to stay in place. Laminated glass is the key safety product for overhead glazing, balustrades and anywhere a broken pane must not fall out. In Singapore, glass used as a barrier must be laminated, a requirement covered in our article on glass railings.

Glass types for heat, light and energy

Singapore’s climate makes solar control as important as safety. Several types of glass and coatings address it:

Body-tinted glass has colourants added to the melt, giving bronze, grey, green or blue tints that absorb part of the solar energy. Absorbed heat raises the glass temperature, which increases thermal stress, so tinted glass is often heat-strengthened.
Reflective glass carries a metallic oxide coating that reflects a share of the sunlight, reducing heat gain but producing a mirror-like appearance by day.
Low-emissivity (low-e) glass carries thin, nearly invisible coatings that reduce the transfer of radiant heat. Solar-control low-e coatings are designed to admit daylight while rejecting much of the infrared. See our guide to low-e glass.
Low-iron glass has reduced iron content, removing the green tinge visible at the edge of ordinary glass. It is used where colour neutrality matters, such as display cases and high-end facades.

Performance is described by the solar heat gain coefficient, light transmittance and thermal transmittance, which together let designers compare products rather than relying on appearance.

Insulating glass units

An insulating glass unit (IGU) consists of two or more panes separated by a spacer and sealed around the edge, with a cavity of dry air or an inert gas such as argon. The cavity reduces heat transfer and, with suitable glass thicknesses and laminated panes, can improve acoustic performance. In the tropics the benefit is mainly in reducing heat gain and noise, rather than retaining heat as in colder climates. Each pane in the unit can be a different type: for example, a laminated inner pane for safety and a coated outer pane for solar control. Our article on double glazing covers this in detail.

The edge seal is the weak point of an IGU. If it fails, moisture enters the cavity and condenses, fogging the unit. Good-quality sealants, careful installation and protection from standing water at the frame all extend its life.

Decorative, specialist and functional glass

Beyond the main structural and thermal types, buildings use a range of other glass:

Patterned or figured glass is rolled with a textured surface to obscure vision while admitting light, often used in bathrooms.
Acid-etched and sandblasted glass have a frosted surface for privacy. Etched surfaces are generally easier to keep clean than sandblasted ones.
Back-painted or enamelled glass is used for splashbacks and cladding; ceramic frit can be fired onto glass during toughening for permanent patterns.
Wired glass has a steel mesh embedded to hold the pane together in a fire. It has largely been superseded by modern fire-resistant products and is not a safety glass in the impact sense.
Fire-resistant glass is designed to maintain integrity, and in some types insulation, for a stated period in a fire.
Switchable glass uses a liquid crystal or electrochromic layer that changes from clear to opaque, or tints, when a voltage is applied.
Self-cleaning glass carries a photocatalytic coating that breaks down organic dirt in sunlight and helps rain sheet off.

Matching the types of glass to the location

The right choice depends on the risk of human impact, what happens if the pane breaks, the heat and light it must control, and how it is supported. A practical way to think about it:

Low-risk windows above waist height in a frame: annealed or coated glass may be acceptable, subject to the relevant codes.
Doors, side panels, low-level glazing and shower screens: safety glass, typically toughened or laminated.
Barriers and balustrades: laminated glass, often with heat-strengthened or toughened plies, so that a broken panel stays in place.
Overhead glazing and skylights: laminated glass on the lower side, so that broken fragments do not fall onto people below.
Load-bearing fins, beams and floors: engineered laminated assemblies designed for post-breakage behaviour, which is the subject of structural glass design.

Codes and standards set the minimum, but the engineering question is always the same: what loads does the pane carry, and what happens next if it breaks?

Frequently asked questions

What are the main types of glass used in buildings?

The main types of glass are annealed float glass, heat-strengthened glass, toughened (tempered) glass and laminated glass, together with coated products such as low-e and reflective glass, body-tinted glass, and insulating glass units made from combinations of these. Decorative and specialist glass, such as patterned, etched and fire-resistant glass, serve particular purposes.

Which type of glass is safest?

It depends on what safe means in the location. Toughened glass is strong and breaks into small, blunt fragments, which reduces cutting injuries. Laminated glass holds together when broken, which prevents falls through barriers and protects people under overhead glazing. Many critical applications use laminated toughened or heat-strengthened glass to get both benefits.

Can toughened glass be cut after it is made?

No. Cutting, drilling, notching and edge-working must all be done before toughening. Attempting to cut toughened glass releases the stored stress and the whole pane shatters, so accurate measurement and templates are essential before ordering.

What glass is required for balcony barriers in Singapore?

Glass used as a barrier in Singapore must be laminated, so that a broken panel remains in place and continues to provide protection. The specification of the plies, interlayer, supports and loads is part of the barrier’s design and should be confirmed by the designer responsible.

Is tinted glass the same as low-e glass?

No. Tinted glass absorbs solar energy through colourants in the glass itself, which darkens it and warms the pane. Low-e glass uses thin coatings that control radiant heat transfer with much less effect on visible light. They can be combined, and their performance is compared using solar heat gain and light transmittance values.

Specifying glazing for a facade, roof, barrier or structural application and need the engineering confirmed? Talk to our consultancy or get in touch.