Catalogue & Reference Guide | 6th Edition QUICK REFERENCE   Symbols | Navigation | Performance data  
GLASS PROCESSING SELECTION PERFORMANCE DESIGN GLAZING COMPLIANCE REFERENCE

2.1           Coating Types

Special coatings can be applied to a float glass surface to make it reflective to short wave radiation from the sun and/or long wave radiation from heat inside or outside the building. These coatings are known by a variety of terms, but there are two main types:

  1. Pyrolytic Coatings
    A coating applied on line at high temperature during the float manufacturing process. Also known as on line or hard coatings.
  2. Sputtered Coatings
    A coating applied off line in special equipment, also known as off line, vacuum, or soft coatings.

Traditional reflective glass has a mirror-like appearance and reflects and absorbs a major proportion of the sun’s direct short wave solar radiation. The degree of reflectivity is dependent on the type of coating and the orientation of the glass. The use of reflective glass is more popular in commercial glazing as it provides superior solar control performance to clear or tinted glass products, and thus improves the energy efficiency of the building.

Low Emissivity (Low E) coatings are traditionally clear and are designed to reflect long wave radiation. They are available in both pyrolytic and sputtered coatings and the performance varies. Some modern reflective glass products have Low E coatings to reflect long wave radiation as well as the sun’s short wave radiation.

In addition, self cleaning coatings are available but these are not reflective, nor Low E. Some special glasses have a sputtered Low E coating applied to the rear surface of a self cleaning coated glass. New developments include UV and scratch resistant coatings such as Climaguard SPF and DiamondGuard SRG. Contact Metro GlassTech for more information.

Design

The building designer should consider several issues when deciding on reflective and coated glass such as:

  • The aesthetics of a reflective glass in relation to the coating reflectivity and orientation of the building. Reflective products can offer the designer a multitude of colour options to enhance or transform a building’s appearance.
  • The performance of the glass to reduce heat gain and cooling costs. Reflective glasses offer superior heat gain performance over tinted glass but this is at the expense of reduced natural daylight levels in a building. In general, reflective glass offers lower UV and visible light transmittance than tinted glass.
  • The ability of the glass to reduce heat loss and heating costs. This can be improved by using Low E coatings or Insulating Glass Units or both.
  • The protection of the coating from damage during construction or cleaning (refer Section 11.5.4 Metro Protect).

Glass alone will not provide all the answers in the design needs of a building. Orientation, overhangs, shading devices and window size all have a bearing on how well a glass product can perform.

 

Pyrolytic reflective glass example

2.2           Pyrolytic Reflective

A pyrolytic coating is a metal oxide coating applied on line during the float manufacturing process. The coating is fused into the glass surface at high temperature making it extremely hard and durable. Since the coating is durable it can be glazed to the outside (surface 1) or inside (surface 2) of the building. It can be handled and cut like standard float glass and processed into heat strengthened, toughened, laminated, curved glass and Insulating Glass Units. These products are also known as an ‘on line’ or ‘hard coat’ reflective glass.

The most common types are the Stopsol and Eclipse ranges. They are available in a range of colours, such as clear, grey, bronze and shades of blue and green. Some manufacturers have different types of pyrolytic coatings, such as Glaverbel, who offer Stopsol Classic, Supersilver and Silverlight coatings.

Colour Differences

Coated glass colours do change when viewed at different times of the day, depending on the weather, surrounding reflections, building orientation and the angle at which the glass is viewed. In addition the appearance is distinctly different if the coating is glazed outside on surface 1 or inside on surface 2. Therefore it is recommended that either a mock-up and/or an on-site visit to a completed building is undertaken when selecting a glass type.

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Symbols

Performance Data Symbols

For more detailed information click on Performance Data or go to Performance.

Visible Light Transmission
Visible Light Transmisson
Visible Light Reflectance
Visible Light Reflectance
Ultra-Violet Elimination
Ultra-Violet Elimination
Fading Reduction Coefficient
Fading Reduction Coefficient
Shading Coefficient
Shading Coefficient
Solar Heat Gain Coefficient
Solar Heat Gain Coefficient
R Value
R Value
U Value
U Value
Sound Transmission Loss
Sound Transmission Loss
Sound Transmission Class
Sound Transmission Class
Weighted Sound Reduction
Weighted Sound Reduction
Coolness Factor
Coolness Factor
Perceived Sound Reduction
Perceived Sound Reduction
Window Efficiency Rating System
Window Efficiency Rating System
   

 

Quick Reference Symbols

Look for these symbols when choosing your glass to help make your decision easier. If you are looking for particular properties in your glass selection make note of the associated icons below. Each glass type has a list of the applicable icons below it's description.

These icons should be used as a general guideline for your selection. You'll also find icons related to special manufacturing parameters including CIP Laminate, Screen Printing and Toughening.

Available Thickness
Available Thickness
Reflective Coating
Reflective Coating
Low E Coated
Low E Coated
Laminated Glass
Laminated Glass
Good Glare Control
Good Glare Control (rated VLT 70% or lower)
Good Fading Reduction
Good Fading Reduction (rated - FRC 0.5 or lower)
Good Solar Control
Good Solar Control (rated S/C 0.6
or lower)
Good Insulation
U Value
(rated - U Value 3.00 or lower)
Condensation Reducing
Condensation Reducing
Good Sounds Reduction
Good Sound Reduction (rated - PSR 40% or higher)
Fire Resistant
Fire Resistant
 
Can Be CIP Laminated
Can Be CIP Laminated
Can Be Screen Printed
Can Be Screen Printed
Can Be Toughened
Can Be Toughened
Can Have Metro Protect
Can Have Metro Protect

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Navigation

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The sixth edition of the Metro Glasstech online catalogue.

 

Product and Service Information

This online catalogue provides a complete guide to Metro GlassTech's product and service range. Every effort has been made to ensure the catalogue is as up to date and comprehensive as possible. If you need any further information, please don't hesitate to contact a Metro GlassTech representative.

Navigation

Finding your way around is easy, with clear headings on each page and a consistent layout in line with our previous catalogue. Each section has a different colour to make it clear where you are in the catalogue. For navigation, page numbers appear at the bottom of each page, along with forward and back buttons.

Reference

Each product has comprehensive relevant technical information, so we have developed a range of quick reference symbols that will assist you in selecting the most appropriate product for your application.

A full explanation for each performance data symbol can be viewed in Performance.

A glass dictionary is provided. This is a useful guide to terms and product names used in the glass industry and throughout this catalogue.

Information Boxes

INFO Information that is considered important is boxed out. Often this is information that is critical when specifying glass so it is advisable to read the info boxes carefully when you see them.

Performance Diagrams

Performance information on many glass products is shown in these performance diagrams. They are a quick way of evaluating the performance of similar glass products.

The diagrams depict a pane of glass with data relating to temperature and solar gain for both the inside and outside.

Refer to performance for comprehensive explanations of the icons used in the performance diagrams.

Example diagram

 

Product Photography

Colour ChartTo the right hand side of each performance diagram is a swatch showing a photographic sample of the glass.

These were photographed specifically for the catalogue to provide as accurate a comparison as possible. Reflective glass types have been shown with a slight reflection.

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Performance Data

Visible Light Transmission Visible Light Transmission
The percentage of visible light transmitted through the glass. VLT is measured in the 380-780nm wavelength range perpendicular to the surface. The higher the percentage the more daylight. Also known as Tv, Tvis, LT and VT.

Visible Light ReflectanceVisible Light Reflection
The percentage of visible light that is reflected by the glass surface, measured in the 380-780nm wavelength range perpendicular to the surface. The VLR can be given as the reflection from the external surface 1 or internal surface 2. The higher the percentage the more reflection. Also known as LR, VR and Rvis

Ultra-Violet EliminationUltraviolet Elimination
The percentage of ultraviolet radiation eliminated by the glass, measured over the 290-380 nm wavelength range. The higher the percentage the less UV is transmitted. This value is calculated from the percentage transmission of ultraviolet (Tuv). Therefore UV Elimination = 100 - Tuv

Fading Reduction CoefficientFading Reduction Coefficient
The ratio of fading reduction of a glass type when compared to the fading protection of 3mm clear float. The FRC of 3mm clear float is by definition 1.0 and represents the minimum fading protection offered by standard glazing. The lower the fading reduction coefficient, the better the fading protection offered.

Solar Heat Gain CoefficientSolar Heat Gain Coefficient
The measure of the total solar energy transmittance entering a building through the glazing as heat gain. It is the total heat transmission of direct solar transmission and that proportion of absorbed radiation that is re-radiated into the building from the action of heat absorbing glass. The lower the SHGC the better the glass restricts heat energy transmission. Also known as the Solar Factor (SF) or g.

Shading CoefficientShading Coefficient
The ratio of the total solar heat gain through a particular glass compared to the total solar heat gain through 3mm clear float glass. (86%) The shading coefficient of 3mm clear float is by definition 1.0 and represents a base glass performance. The lower the shading coefficient the less heat gain and thus more shading is provided by the glass. The shading coefficient is calculated as SC = SHGC / 0.86

Window Efficiency Rating SystemWindow Efficiency Rating System
The complete WERS rates the performance of windows including frames in various defined New Zealand climate zones. For this catalogue star ratings apply to centre of glass only (WERS cog) to compare glass types and a maximum rating of five stars indicates the best performance possible. Ratings in star and half star values are given, with five stars indicating the premium performance. Refer Section 12 (Page 105) for a full explanation of each star type.

U ValueU Value
The U Value is the measure of air to air heat transfer through glass due to the thermal conductance of the glazing and the difference between indoor and outdoor temperatures. It is expressed as W/m2K (Watts per m2 per 1° Kelvin) or W/ m2 °C. 1 Kelvin equals 1°C. The U value is a measure of the rate of heat gain or heat loss through the glazing due to environmental differences between outdoor and indoor air. It is measured at the centre of the glass (cog).The lower the U Value the lower the heat transfer, the better the insulation.

Coolness FactorCoolness Factor
The Coolness Factor (or luminous efficacy) is the visible light transmission divided by the shading coefficient.
CF = VLT / SC. It is a useful means of comparing different glass types in terms of the trade-off between light transmission and heat control in selecting glass. Glass types with a coolness factor of 1 transmit as much light as heat, those with a coolness factor lower than 1 transmit more heat than light and those with a coolness factor greater than 1 transmit more light than heat

R ValueR Value (Total Thermal Resistance)
The R Value is the value of thermal resistance of a building element which is the sum of the surface resistances on each side plus each component of a building element. It is the inverse of the U Value R=1/R and is expressed as m2 °C/W.

Sound Transmission LossSound Transmission Loss
The average Sound Transmission Loss is useful for determining the effectiveness of glazed panels to isolate exterior noise (e.g. traffic) from a building. It is derived from the average of the measured transmission loss at eighteen 1/3 octave frequency bands between 100Hz and 5000Hz, or 16 bands from 125 to 4000Hz. Average STL is measured in decibels (dB), the higher the average STL figure, the more effective glazing will be in reducing sound transmission.

Sound Transmission ClassSound Transmission Class
The Sound Transmission Class is useful for determining the noise reduction offered by internal building elements such as partitions and walls. It is a measure that relates the sound reduction performance against sounds which normally occur inside a building (such as voices, telephones, music etc). STC is a numerical class rating and cannot be compared with the STL. It is derived from a best fit curve comparison of a reference STC curve to the insulation curve. The higher the STC rating, the better the overall sound reduction.

Weighted Sound ReductionWeighted Sound Reduction Index
The Weighted Sound Reduction Index incorporates frequency modified correction for the human ear’s response. The RW is reported in dB and is a composite rating of sound reduction at frequencies from 100 - 5000Hz. Numerically, it is comparable to the STC values but the numbers are in dBA.

Perceived Sound ReductionPerceived Sound Reduction
The percentage by which the human ear detects a lessening in sound pressure or noise is known as the Perceived Sound Reduction. A 10dB reduction in sound pressure level is generally perceived as a halving of the original noise. Sound reduction values are ‘weighted’ and used to calculate the perceived sound reduction as a ratio relative to the RW for 3mm clear float. The dB difference in the RW value for a glass type when compared to 3mm float is calculated as a perceived sound reduction percentage. For other sound indices see Section 11.4.5 and 11.4.6

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