Glass Selection Guide

Selecting the right glass...

Glass plays a unique and important role in building design and the environment. It affects design, appearance, thermal performance and occupant comfort. The selection of the right glass is a crucial component of the design process.

By identifying key issues at the design stage, glass products can be selected to match your specific application.

The following selection guide is courtesy of Metro Glasstech.

Architectural Glass Selection:

This selection guide uses key design criteria to assist in the selection of glass. First, consider the key points in each step. Steps may conflict, so next, arrange them into an order of priority using the glass selection flow chart. Finally, select the appropriate glass combination.

Step 1: Heat Loss

Step 1: Heat Loss - Select the insulation you require to reduce heat loss.

  • Single monolithic glass provides poor insulation
  • Laminated glass does not improve insulation
  • Low E glass improves insulation
  • Insulation of housing thermal envelopes must comply with NZS 4218
  • Insulating Glass Units provide the best insulation
  • Larger air space (up to 16mm) provides better insulation
  • Argon is better than air for insulation (12mm optimum)
  • Argon and Low E can be combined for higher performance
  • Insulation is measured by the U Value. The lower the number the better
  • Insulation can be measured by the R Value. The higher the number the better
  • Internal blinds and drapes may help reduce heat loss but only if installed correctly


Step 2: Comfort & Condensation

Step 2: Comfort & Condensation - Select the insulation to help reduce condensation.

  • Single glass provides poor condensation control without air conditioning and dehumidification
  • Single Low E glass can increase condensation
  • Condensation can reduce the performance of Low E glass
  • Insulating Glass Units provide the best comfort and condensation control
  • The better the insulation the less cold zones near windows
  • The better the insulation the more comfortable the environment
  • The better the insulation the less condensation will occur
  • Low E glass and Argon gas further reduce condensation


Step 3: Heat Gain

Step 3: Heat Gain - Select the shading coefficient you require to reduce heat gain.

  • The lower the shading coefficient (SC) the lower the heat gain
  • Tinted glasses are better than clear glass
  • Dark tinted glasses are normally better than standard tints
  • High performance tints are normally better than standard tints
  • Reflective glasses are better than tinted glasses
  • Insulating Glass Units help reduce heat gain
  • Low E glass can help reduce heat gain
  • A low shading coefficient will normally mean less natural light
  • External shading devices can help reduce heat gain


Step 4: Glare

Step 4: Glare - Select the light transmission you require to reduce glare.

  • The lower the visible light transmission (VLT) the lower the glare
  • The lower the light transmission the lower the natural light
  • Shading can help reduce direct sun glare but not diffused light
  • Green and blue tints generally have higher light transmission
  • Grey and bronze tints generally have lower light transmission
  • Reflective glasses can create external and internal reflectivity issues
  • Insulating Glass Units slightly reduce the light transmission
  • Low-E glass slightly reduces light transmission
  • Reflective glasses can cause internal glare at night


Step 5: Fading

Step 5: Fading - Select the UV elimination you require to reduce fading.

  • The higher the UV elimination the lower the level of fading
  • Shortwave UV creates the most fading
  • The lower the visible light the lower the level of fading
  • The lower the heat gain the lower the level of fading
  • Insulating Glass Units help reduce fading
  • Low-E glass can help reduce fading
  • Tinted glass helps reduce fading
  • Reflective glass helps reduce fading


Step 6: Acoustics

Step 6: Acoustics - Select the sound reduction you require to reduce noise.

  • Thicker glass will help reduce noise
  • Laminated glass will help reduce noise
  • Insulating Glass Units will help reduce noise
  • Different glass thickness plies in an IGU will help reduce noise
  • The higher the STL, STC or RW value the better
  • Use the perceived sound reduction (PSR) information to compare values


Step 7: Safety

Step 7: Safety - Select the glass type you require for safety.

  • Use NZS 4223: Part 3 to select the glass type for human impact safety
  • Use the NZSGA Flow Chart to help select glass type
  • Toughened and Laminated glass are both Grade A Safety Glasses
  • An IGU can have one or both sides with Safety Glass depending on the impact location
  • Use Safety Glass for sloped and overhead glazing
  • Special safety glasses can also provide levels of security


Step 8: Aesthetics

Step 8: Aesthetics - Select the colour for the required look.

  • Clear glass provides the most transparent look
  • Extra Clear low iron glass provides pure clarity
  • Tinted glasses are available in different shades of colour
  • Grey and bronze tints provide the darkest colours
  • Blue and green tints provide the lightest colours
  • The thicker the tinted glass the darker the tint colour
  • Low E glass has a slight reflectivity
  • Reflective glass varies in colour depending on the orientation of the coated surface
  • Reflective glasses can create special effects by reflecting images
  • Reflective glasses can cause internal reflection issues at night
  • Heat treating can create distortion in the glass
  • IGU pressure changes can create distortion in the glass


Step 9: Glass/Unit Size

Step 9: Glass/Unit size - Select the maximum glass size for the glass type.

  • Determine the wind zone or wind load for your project
  • Use NZS 4223: Part 3 to select the glass size for safety
  • Use NZS 4223: Part 4 to select the glass for wind loads and dead loads
  • Check size limitations for glass types
  • An IGU can be 1.5 times the area selected for single glass
  • Use the unit thickness selected in the above steps
  • Check the unit combination complies with the max large and small dimensions in the chart. If not reduce the size to comply
  • Check the size also complies with Step 7 above