Glass, Windows & Doors

Glass

Amorphous Solid

  • Glass is an amorphous solid, lacking a definite shape or organized atomic structure.
  • It resembles a supercooled liquid, which accounts for its transparency and brittleness.

Types of Glass

  • Soda-Lime-Silica Glass:
    • Composition: Silica (74%), Soda (15%), Lime (10%), Alumina (1%).
    • Properties: Inexpensive, chemically stable, easily workable, and recyclable.
    • Uses: Windows, bottles, and jars.
  • Lead-Alkali-Silica Glass:
    • Composition: Contains 18-40% lead oxide (PbO).
    • Properties: Lower melting point, improved density, high refractive index, and electrical resistance.
    • Uses: Decorative items, crystal glassware, and optical lenses.
  • Borosilicate Glass (e.g., Pyrex):
    • Composition: Includes boron trioxide.
    • Properties: Resistant to thermal shock and chemical corrosion.
    • Uses: Laboratory glassware, cookware, and high-temperature applications.

Properties of Glass

  • Transparent (typically 86-89%)
  • Heat transfer through conduction, convection & radiation
  • Chemical resistance (except hydrofluoric acids)
  • Strong (can be increased through heating processes)
  • Not porous
  • Flexible
  • High embodied energy (but fully recyclable)

Glass Strengthening

  • Annealed Glass:
    • Process: Slow cooling of hot glass to relieve internal stresses.
    • Benefits: Reduces risk of cracks or shattering.
    • Uses: Standard windowpanes and glass doors.
  • Tempered Glass:
    • Process: Heating glass to 600-720°C and rapidly cooling it.
    • Benefits: 3-5 times stronger than regular glass, shatters into small, blunt pieces.
    • Uses: Car side windows and Shower screens.
  • Laminated Glass:
    • Process: Sandwiching a plastic interlayer (PVB) between two glass layers, then heating and pressurizing.
    • Benefits: Glass stays attached to the interlayer when broken, reducing injury risk.
    • Uses: Windshields and skylights.

Energy Transfer

  • Transmission: Amount of light passing through glass.
  • Reflection: Amount of light reflected off the surface.
  • Radiation: Emission or absorption of thermal energy.
  • Solar Heat Gain: Amount of solar energy entering through the glass.

Glass Failure

  • Impact from moving objects
  • Wind load (storms, tornadoes)
  • Thermal expansion
  • Poor installation
  • Impurities (air bubbles, Nickel Sulphate)

History of Glass

  • 2600 BC: Glassmaking emerges in Mesopotamia.
  • Mid-2000s BC: Glass beads appear in Egypt.
  • 1st Century BC: Glassblowing is invented in Syria.
  • 1st-3rd Centuries AD: Glassblowing spreads to Egypt.
  • 15th Century AD: Angelo Barovier invents transparent glass in Venice.
  • 19th Century: Mass production of glass begins.
  • 20th Century: Glass is used in windows, doors, cars, computers, and mobile phones.

Float Glass

  • Invented by Alistair Pilkington (1952-59).
  • Process: Floating molten glass on molten tin to create a flat ribbon.
  • Global standard for high-quality glass manufacturing.

Windows and Doors

  • Essential for entry, exit, light, and ventilation.

Window Tax

  • Property tax based on the number of windows, used in England, France, Ireland, and Scotland during the 18th and 19th centuries.