Glazed Performance Strategies

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Glazed Performance Strategies
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History

• The first continuous production of glass panes
  began in 1906.
• In 1959 the float glass process was introduced.
• 1970s values of thermal resistance of walls and
  windows were expressed as moderate,
  sufficient and good.
• Low emmissivity coatings began in 1981.
• Thermal insulation improves after energy crisis
  and higher energy prices in the late 70s.

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The Use of Glass in Architecture

• lighting
• Visual comfort
• Thermal comfort
• Resistance to wind loads and operating forces
• Protection against noise
• Security
• Fire-safety
• Aesthetic aspects

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Energy Performance

• 3 major types of climatic conditions
• Solar heat gains in the form of radiation
• Heat losses in the form of conduction, convection
  and radiation
• Air flow both intentional (ventilation) and
  unintentional (infiltration)

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Energy Performance Gas-fills

• Transparent insulation material (TIM)
• Honeycomb or capillary structure made of glass
  or plastics
• High solar transmittance
• Reduced heat loss and infrared radiation
• Good illumination can be achieved, but no clear
  view
• Silica Aerogel microporous material that traps
  air in tiny holes
• Good optical clarity, solar transmittance
• Excellent insulating properties

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Energy Performance electrically heated glazing

• Metal oxidized layer on coating
• Electric current is applied
• Prevents cold draught of the cold glazing
  surface
• Can be used for heating too
• Melt snow away

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Light Transmission

• Light transmission is the principal property of
  glass in architecture, and one which has proved
  difficult to master over the
  centuries. M.Wigginton

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Light Transmission Low emission coatings

• Low-e coatings consist of very thin, transparent
  layers of metals or oxides deposited on glass or
  plastic.
• Reduce ability of the material to transfer heat
  through infrared radiation to the outside.
• Decrease overall u-value

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Light Transmission Chromogenic materials

• Photochromic coatings change the solar
  transmittance as a function of light intensity
  (like sunglasses). Used for visual comfort.
• Thermochromic materials change their optical
  properties as a function of their temperature,
  from transparent when cool to a white,
  reflecting/diffusing state when heated.
• Gasochromic glazng in these a low concentration
  of hydrogen in a neutral gas such as nitrogen is
  dissociated by a catalyst and intercalated into a
  tungsten layer. It turns deep blue.

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Light Transmission

• Electrochromic materials multi-layer films whose
  optical can be controlled using applied voltage
  (like a flat display panel).
• Great versatility because their transmittance can
  be controlled at any time.
• Complex, difficult to fabricate, and expensive

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Light Transmission
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Light Transmission

• Liquid crystals similar technology as l.c.d
  monitors.
• When powered off the glass is opaque
• When powered on glass is transparent
• Can use high amounts of power in larger surfaces.

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Light Transmission
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Refractive Index

• Is the measure of the amount by which light is
  bent as it passes through a glass and is
  comparatively constant for most glasses
• 1.52 for soda-lime glasses
• Varies according to wavelength of the radiation

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Other Strategies