GLASS SELECTION GUIDE - Eboss

GLASS SELECTION GUIDE
www.metroglasstech.co.nz

GLASS SELECTION
The Glass Selection Flow Chart should be used in conjunction with the Selection Sheets and Section 11.1.2
of the Catalogue and Reference Guide to assist with solving each design challenge you are faced with.
FLOW CHART
Circle priority number in each step. Each step is detailed in 11.1.2 Glass Selection Guide. Priority 1 = Highest, Priority 5 = Lowest
Start here
Go to
Step 1
Do you want to
Reduce Heat Loss
Priority 1 2 3 4 5
Yes
Circle priority 1-5
and go to Step 2
No
Step 2
Do you want to
Control Condensation
Priority 1 2 3 4 5
Yes
Circle priority 1-5
and go to Step 3
No
Step 3
Do you want to
Reduce Heat Gain
Priority 1 2 3 4 5
Yes
Circle priority 1-5
and go to Step 4
No
Step 4
Do you want to
Reduce Glare
Priority 1 2 3 4 5
Yes
Circle priority 1-5
and go to Step 5
No
Step 5
Do you want to
Reduce Fading
Priority 1 2 3 4 5
Yes
Circle priority 1-5
and go to Step 6
No
Step 6
Do you want to
Reduce Noise
Priority 1 2 3 4 5
Yes
Circle priority 1-5
and go to Step 7
No
Step 7
Do you want to
Increase Safety
Priority 1 2 3 4 5
CIP
Yes
Circle priority 1-5
and go to Step 8
Step 8
Do you want to
No
Improve Aesthetics
Priority 1 2 3 4 5
Yes
Circle priority 1-5 ,
select colour preference
and go to Step 9
No
What glass colour is preferred
Clear
Blue Dark Medium Light
Green Dark Medium Light
Bronze Dark Medium Light
Grey Dark Medium Light
Reflective High Medium Low
Step 9
Do you want to
Glaze Large Windows
Priority 1 2 3 4 5
Yes
Circle priority 1-5, fill in detail
and go to FINISH
No
FINISH
Largest window size=height
Windzone or windload
x width
www.metroglasstech.co.nz
April 2013

PERFORMANCE
The Performance Data Graph below is designed to enable key performance properties of different glass
types to be plotted and compared with each other. The performance data can be taken from Section 12
of the Catalogue and Reference Guide or from other reliable sources.
The plotted glass performance can be compared with the ‘Rating Zone’ which gives a guide to good
all-round performance of the glazing.
Note: In some cases specific design requirements may mean the ideal glass is outside the ‘Rating Zone’.
Performance
Glass Type Glass type
Quick Reference Symbols heat loss &
fading glare heat gain condensation acoustics
%
Rating Zone
FRC VLT SC U PSR
From:
fading visable Performance shading Data Symbols
reduction light coefficient
coefficient transmission
Notes:
u value
percieved
sound
reduction
Phone:
www.metroglasstech.co.nz
April 2013

HEAT LOSS
(INSULATION)
Heat Loss from the thermal envelope is a key factor in modern housing design.
In winter the Insulating Glass Unit can trap heat inside the house and thus reduce the amount
of heating required (kWh) to maintain a comfortable environment.
In summer the Insulating Glass Unit can trap the cool air inside the house and reduce the amount
of cooling required to maintain a comfortable environment.
In all seasons the Insulating Glass Unit can reduce the energy loads on Heating, Ventilating and
Air Conditioning (HVAC) systems.
GOOD
4mm clear
12mm airspace
4mm clear
Solution:
GlassTech IGU
Is GOOD because it meets the minimum
requirements for thermal insulation for
housing and small buildings (NZS 4218).
INNER
OUTER
BETTER
4mm Low E
12mm airspace
4mm clear
Solution:
GlassTech Low E + IGU
Low E glass provides BETTER thermal
insulation as it traps the heat inside by
reflecting long wave radiation.
INNER
OUTER
BEST
4mm Low E
INNER
12mm Argon
4mm clear
OUTER
Thermal
spacer
Solution:
GlassTech Low E + IGU
and Argon +
By combining Low E glass and argon gas
the BEST thermal insulation is achieved.
Thermal spaces can be used in thermally
efficient frames to improve the total
window performance.
www.metroglasstech.co.nz April 2013

PERFORMANCE DATA
The following tables compare the insulation performance of clear glass IGUs, for a range of air or argon
spaces. The heat loss reduction % compares the heat loss (U Value) to that of single 4mm clear glass.
Changing the glass thickness will have minimal effect on the insulation.
GOOD
12mm airspace
4mm clear 4mm clear
Insulation comparison
Type
Outer Glass
(mm)
Air Space
(mm)
Inner Glass
(mm)
U Value*
Heat Loss
Reduction**
4 Clear 6 4 Clear 3.15 46%
4 Clear 8 4 Clear 2.94 50%
OUTER
INNER
1 2 3 4 surface
#
GlassTech IGU
4 Clear 10 4 Clear 2.83 52%
4 Clear 12 4 Clear 2.73 54%
4 Clear 14 4 Clear 2.70 54%
4 Clear 16 4 Clear 2.72 54%
BETTER
12mm airspace
4mm clear 4mm Low E
Insulation comparison
Type
Outer Glass
(mm)
Air Space
(mm)
Inner Glass
(mm)
U Value*
Heat Loss
Reduction**
4 Clear 6 4 N70 Low E 2.56 57%
4 Clear 8 4 N70 Low E 2.24 62%
OUTER
INNER
1 2 3 4 surface
#
GlassTech Low E +
IGU (Climaguard
N70 Low E # 3)
4 Clear 10 4 N70 Low E 2.07 65%
4 Clear 12 4 N70 Low E 1.92 67%
4 Clear 14 4 N70 Low E 1.93 67%
4 Clear 16 4 N70 Low E 1.96 67%
BEST
12mm Argon
4mm clear 4mm Low E
Insulation comparison
Type
Outer Glass
(mm)
Argon Space
(mm)
Inner Glass
(mm)
U Value*
Heat Loss
Reduction**
4 Clear 8 4 N70 Low E 1.90 68%
OUTER
INNER
1 2 3 4 surface
#
GlassTech Low E +
Argon + IGU
(Climaguard N70
Low E # 3)
4 Clear 10 4 N70 Low E 1.77 70%
4 Clear 12 4 N70 Low E 1.68 72%
4 Clear 14 4 N70 Low E 1.71 71%
4 Clear 16 4 N70 Low E 1.73 71%
* U Values are centre of glass values in W/m2K calculated on Thermal 5.2.6 software using NFRC 100-2004 conditions - Argon spaces are 90% argon and 10% air.
** Heat Loss Reduction is calculated compared to 4mm clear float (U value = 5.89).
# Surface number.
The Good, Better, Best approach is a simplification of the complexity surrounding the selection of the
correct glass to provide the best design solution, and therefore other options, not listed on this sheet, are
available from Metro GlassTech. In addition other factors can affect the glass selection such as the risk
of thermal stress breakage and the requirements to comply with the NZ Building Code and NZS 4223.
www.metroglasstech.co.nz
April 2013

CONDENSATION
Internal condensation that forms on glazing is a key factor in modern housing design.
Condensation can damage fabrics, furnishings and framing and create an unhealthy environment.
Condensation is a function of relative humidity (%RH) of the air, the indoor and outdoor temperature and the
insulation properties (U value) of the glazing.
Insulating Glass Units can reduce the onset of internal condensation by keeping the interior glass surface warmer.
GOOD
Clear glass
INNER
Clear glass
OUTER
Solution:
GlassTech IGU
Is GOOD because it meets the
minimum requirements for thermal
insulation for housing and small buildings
(NZS 4218) and keeps the inside glass
surface warmer than single glazing.
BETTER
Low E glass
Clear glass
Solution:
GlassTech Low E + IGU
Low E glass provides BETTER thermal
insulation as it traps heat inside by
reflecting long wave radiation and
keeping the inner glass warmer.
INNER
OUTER
BEST
Low E glass
INNER
Argon gas
Clear glass
OUTER
Solution:
GlassTech Low E + and Argon + IGU
By combining Low E glass and argon gas the
BEST thermal insulation is achieved and the
inner glass at it warmest.
Thermal spacers can be used in thermally
efficient frames to improve the total window
performance, and the edge area condensation
that can occur with normal windows.
PERFORMANCE DATA – Refer to Metro GlassTech Catalogue and Reference Guide Section 11.2.5.
External dew (which is sometimes known as external condensation) can occasionally occur on the outside of high performance
Insulating Glass Units in temperate climates.
The Good, Better, Best approach is a simplification of the complexity surrounding the selection of the
correct glass to provide the best design solution, and therefore other options, not listed on this sheet, are
available from Metro GlassTech. In addition other factors can affect the glass selection such as the risk
of thermal stress breakage and the requirements to comply with the NZ Building Code and NZS 4223.
www.metroglasstech.co.nz
April 2013

CONDENSATION
Air is a mixture of gases including water vapour. At any given
temperature there is a limiting maximum vapour pressure,
called the saturated vapour pressure, where the air cannot
hold any more water vapour. If air, containing water vapour,
comes into contact with a cooler surface the excess moisture
is deposited on the surface as condensation.
The surface temperature at which condensation begins to
form is called the “Dew Point”. The ratio of the water vapour
pressure at room temperature to the saturated water vapour
pressure at that temperature is known as the “Relative
Humidity” (RH), and is expressed as a percentage.
Relative Humidity is a measure of the water content of the air
at a given temperature. Many domestic activities, such as
cooking and washing, will liberate water vapour and increase
the relative humidity and thus the occurrence of condensation.
In all cold temperature climates, condensation can occur on
the inside of windows when the external temperature falls
significantly below the internal temperature and cools the glass.
The onset of condensation on the interior glass surface
can be controlled either by reducing the humidity, thereby
lowering the dew point, or by raising the inside glass surface
temperature. The latter can be achieved by increasing the
insulation of the window by the use of an Insulating Glass
Unit as the lower the glass U Value the less the risk of
condensation forming.
GlassTech IGU’s reduce the likelihood of condensation
forming by providing a thermal barrier between the inside and
outside. The use of Argon Gas and/or Low E glass further
enhances the U Value performance, making the inner glass
warmer, and thus helping to inhibit condensation.
CONDENSATION PREDICTION CHART
2.0 1.0
5.0
4.0
3.0
U Value
6.0
-30
-25
-20
-15
-10
-5
0
5
10
15
20
25
30
-10 -5 0 5 10 15 20 25 30
10 20 30 40 50 60 70 80 90
Inside Temperature (˚C) Relative Temperature (%)
When the internal air temperature is 20ºC and the relative humidity is 60%, condensation will not form on double glazed units with the U Value 3.0 W/m2K until the external
temperature falls below -2ºC. Under the same internal conditions, condensation will form on single glass with U Value 5.8 W/m2K when the external temperature falls below 10ºC.
The four parameters for predicting the conditions
under which condensation will occur are:
1. Inside air temperature
2. Outside air temperature
3. Indoor relative humidity
4. U Value of the glazing.
If any 3 are known the other is derived from the chart above.
How to reduce internal condensation
• Provide natural ventilation through an opening window
or proprietary ventilating unit during the day to permit
air changes.
• In cold weather heat the rooms and keep the inner glass
surface warm.
• Keep the rooms heated if possible and an insulating
glass unit will retain the heat.
• Use HVAC systems to control temperature and humidity.
• Ventilate gas heaters.
• Use heaters that provide warm dry air.
• Use dehumidifiers until the air is dryer, this helps the
temperature as dry air is warmer.
• Fit extraction systems in cooking and bathrooms areas.
• Draft proof external doors and windows to prevent damp
humid air getting inside.
• Draft proof internal doors and keep closed if near
kitchens and laundry areas.
• If using heavy drapes and curtains allow the warm air to
circulate between the drapes and glass by ventilating with
a 20mm min gap and open gaps at the top and bottom.
• If using radiators, position them near to the glass so the
inner glass is warm.
• Use thermally efficient frame materials or designs to
reduce frame condensation.
www.metroglasstech.co.nz
April 2013

HEAT GAIN
(SOLAR CONTROL)
Heat gain from the sun is a key factor in modern housing design.
In winter the Insulating Glass Unit can allow the sun to warm the house and thus reduce the amount
of heating required (kWh) to maintain a comfortable environment.
In summer the Insulating Glass Unit can control the sun’s heat, with the help of special solar control
glasses and thus reduce the amount of cooling required to maintain a comfortable environment.
In all seasons the Insulating Glass Unit can reduce the energy loads on Heating, Ventilating and Air
Conditioning (HVAC) systems. Building shading, blinds and drapes can also be used to reduce heat
gain, but care is required to ensure thermal stress breakage does not occur in the glass.
GOOD
Clear glass
INNER
Low E glass
OUTER
Solution:
GlassTech Low E + IGU
Low E glass such as Climaguard N70
used as the outer pane of the IGU with the
coating on surface 2 is good as it will
reduce the solar heat gain, by lowering
the shading coefficient of the glazing.
BETTER
Clear glass
INNER
Tinted glass
OUTER
Solution:
GlassTech Tinted IGU
Tinted glass used as the outer pane of
the IGU is better as it absorbs solar
energy and will reduce the solar heat gain,
by lowering the shading coefficient of the
glazing. Tinted glasses vary in colour and
performance, with the most common being
grey, bronze and green for housing.
BEST
Low E glass
INNER
Tinted glass
OUTER
Solution:
GlassTech Tinted Low E + IGU
By combining tinted glass and
Low E coatings the best heat gain
performance can be achieved.
In addition reflective glasses can be used
as they are the VERY BEST but they are
not common for housing.
www.metroglasstech.co.nz April 2013

PERFORMANCE DATA
The following tables compare the Shading Coefficient (SC) performance for a range of solar control
IGUs. The Shading Coefficient compares the solar heat gain of the glass with that of 3mm clear float
glass which has a SC of 1. Changing the air space will have minimal effect on the SC.
GOOD
shading coefficient comparison
Low E glass
Clear glass
Type
Outer Glass
(mm)
Air Space
(mm)
Inner Glass
(mm)
Shading
Coefficient
- - 3 Clear 1.00
4 Clear 12 4 Clear 0.89
OUTER
INNER
1 2 3 4 surface
GlassTech Low E +
IGU (Climaguard
N70 Low E # 2)
The above data has been included for reference
4 N70 Low E 12 4 Clear 0.63
5 N70 Low E 12 5 Clear 0.62
BETTER
shading coefficient comparison
Tinted glass
Clear glass
Type
Outer Glass
(mm)
Airspace
(mm)
Inner Glass
(mm)
Shading
Coefficient
5 Grey 12 4 Clear 0.61
6 Bronze 12 4 Clear 0.59
GlassTech Tinted
5 Green 12 5 Clear 0.59
OUTER
INNER
IGU
6 Grey 12 5 Clear 0.56
1 2 3 4 surface
6 Blue 12 5 Clear 0.53
5 Evergreen 12 4 Clear 0.50
BEST
shading coefficient comparison
Tinted glass
Low E glass
Type
Outer Glass
(mm)
Airspace
(mm)
Inner Glass
(mm)
Shading
Coefficient
4 Green 12 4 N70 Low E 0.54
OUTER
INNER
1 2 3 4 surface
GlassTech Tinted
Low E + IGU
(Climaguard N70
Low E # 3)
5 Bronze 12 4 N70 Low E 0.53
4 Grey 12 4 N70 Low E 0.52
5 Green 12 5 N70 Low E 0.50
5 Grey 12 5 N70 Low E 0.47
5 Evergreen 12 5 N70 Low E 0.42
*Shading Coefficients are calculated on Thermal 5.2.6 software using NFRC 100-2004 conditions and will vary with glass type.
** The shading coefficient compares the solar heat gain of the glass with that of 3mm clear float glass.
# Surface number
For more options refer to the Catalogue and Reference Guide – Section 12
The Good, Better, Best approach is a simplification of the complexity surrounding the selection of the
correct glass to provide the best design solution, and therefore other options, not listed on this sheet, are
available from Metro GlassTech. In addition other factors can affect the glass selection such as the risk
of thermal stress breakage and the requirements to comply with the NZ Building Code and NZS 4223.
www.metroglasstech.co.nz April 2013

GLARE
(Visible light)
Glare caused by bright sunlight is a key factor in modern housing design.
Large areas of glazing are great for views and sunlight but if not controlled by shade or orientation they
can create very bright light and glare inside the home.
Low angle morning summer sun from the east and low angle winter sun from the west can be difficult to
control without using solar control glass, blinds or drapes.
Glare is a function of the glass Visible Light Transmission (VLT) and the sun’s incidence on the glass.
GOOD
Clear glass
INNER
Low E glass
OUTER
Solution:
GlassTech Low E+ IGU
Low E glass such as Climaguard N70
is used in the IGU with the coating on
surface 2 or 3 is GOOD as it will reduce
the visible light transmission (VLT) of the
glazing and reduce the glare from the sun.
BETTER
Clear glass
INNER
Tinted glass
OUTER
Solution:
GlassTech Tinted IGU
Tinted glass used as the outer pane of the
IGU is better as it reduces the visible light
transmission (VLT) even further depending on
the tint colour and thickness.
Tinted glasses vary in colour and performance,
with the most common being grey, bronze,
blue and green for housing.
BEST
Low E glass
INNER
Tinted glass
OUTER
Solution:
GlassTech Tinted Low E+ IGU
By combining tinted glass and Low E
coatings a further reduction in VLT can
be achieved.
In addition reflective glasses can be used
as they are the VERY BEST but they are
not common for housing.
www.metroglasstech.co.nz April 2013

PERFORMANCE DATA
The following tables compare the percentage Visible Light Transmission (VLT) for a range of IGUs.
GOOD
VLT Comparison
Low E glass
Clear glass
Type
Outer Glass
(mm)
Air Space
(mm)
Inner Glass
(mm)
VLT %
– – 3 Clear 90
4 Clear 12 4 Clear 80
OUTER
INNER
1 2 3 4 surface
GlassTech Low E +
IGU (Climaguard
N70 Low E # 2)
The above data is included for reference
4 N70 Low E 12 4 Clear 69
4 Clear 12 4 N70 Low E 69
BETTER
VLT Comparison
Tinted glass
Clear glass
Type
Outer Glass
(mm)
Air Space
(mm)
Inner Glass
(mm)
VLT %
5 Green 12 5 Clear 71
5 Evergreen 12 4 Clear 64
GlassTech Tinted
4 Grey 12 4 Clear 51
OUTER
INNER
IGU
5 Grey 12 4 Clear 45
1 2 3 4 surface
5 Bronze 12 4 Clear 53
6 Blue 12 4 Clear 52
BEST
VLT Comparison
Tinted glass
Low E glass
Type
Outer Glass
(mm)
Air Space
(mm)
Inner Glass
(mm)
VLT %
5 Green 12 4 N70 Low E 59
OUTER
INNER
1 2 3 4 surface
GlassTech Tinted
Low E + IGU
(Climaguard N70
Low E # 3)
5 Evergreen 12 4 N70 Low E 54
4 Grey 12 4 N70 Low E 43
5 Grey 12 4 N70 Low E 38
5 Bronze 12 4 N70 Low E 45
6 Blue 12 4 N70 Low E 44
* VLT is calculated from Thermal 5.2.6 software using NFRC 100-2004 conditions and will vary with glass type.
# Surface number
For more options refer to the Catalogue and Reference Guide – Section 12
The Good, Better, Best approach is a simplification of the complexity surrounding the selection of the
correct glass to provide the best design solution, and therefore other options, not listed on this sheet, are
available from Metro GlassTech. In addition other factors can affect the glass selection such as the risk
of thermal stress breakage and the requirements to comply with the NZ Building Code and NZS 4223.
www.metroglasstech.co.nz April 2013

FADING
(UV ELIMINATION)
Fading caused by the sun’s solar radiation is a key factor in modern housing design.
The main cause of fading is ultraviolet light (UV) but visible light, infrared radiation, humidity and
pollutants all play a part.
Insulating Glass Units can reduce the amount of radiation entering the home, by using a combination
of glass types. In general terms, the lower the Fading Reduction Coefficient the less fading occurs.
GOOD
Clear laminated
Clear glass or
Low E glass
Solution:
GlassTech Laminated IGU
Laminated glass is good because the
PVB interlayer absorbs UV light.
Low E glass is good because the
coating reduces UV transmission.
INNER
OUTER
BETTER
Clear glass or
Low E glass
INNER
Tinted glass
OUTER
Solution:
GlassTech Tinted IGU
Tinted glass is better depending on
the tint colour and type as it absorbs UV,
visible and infrared radiation.
Low E glass helps to reduce the UV
transmission even further.
BEST
Clear laminated
INNER
Tinted glass
OUTER
Solution:
GlassTech Tinted & Laminated IGU
By combining tinted glass and laminated
glass the best fading reduction can be
achieved.
In addition reflective glasses can be used
as they are the VERY BEST but they are not
common for housing.
www.metroglasstech.co.nz
April 2013

PERFORMANCE DATA
The following tables compare the Fading Reduction Coefficient (FRC) for a range of IGU’s. The FRC
compares the fading reduction of the glazing with 3mm clear glass, which has a FRC of 1. The lower the
FRC the lower the rate of fading.
GOOD
Fading comparison
Clear glass
or Low E
Clear
laminated
Type
Outer Glass
(mm)
Air Space
(mm)
Inner Glass
(mm)
FRC**
- - 3 Clear 1.00
OUTER
INNER
GlassTech
Laminated IGU
with Clear glass
or ClimaGuard
N70 Low E
4 Clear 12 4 Clear 0.78
The above data is included for reference
4 N70 Low E 12 4 Clear 0.65
5 Clear 6 6.38 Lam 0.40
5 Clear 12 6.38 Lam 0.40
BETTER
Fading comparison
Tinted
glass
Clear glass
or Low E
Type
Outer Glass
(mm)
Air Space
(mm)
Inner Glass
(mm)
FRC**
6 Bronze 12 6 Clear 0.36
OUTER
INNER
GlassTech Tinted
IGU with Clear glass
or ClimaGuard
N70 Low E
5 Grey 12 4 Clear 0.39
6 Evergreen 12 6 Clear 0.34
6 Grey 12 6 Clear 0.34
5 Grey 12 4 N70 Low E 0.31
BEST
Fading comparison
Tinted
glass
Clear
laminated
Type
Outer Glass
(mm)
Air Space
(mm)
Inner Glass
(mm)
FRC**
5 Evergreen 12 6.38 Lam 0.25
OUTER
INNER
GlassTech Tinted
& Laminated
IGU
5 Bronze 12 6.38 Lam 0.25
5 Grey 12 6.38 Lam 0.24
6 Grey 12 6.38 Lam 0.22
* UV elimination is calculated from Thermal 5.2.6 software using NFRC 100-2004 conditions and will vary with glass type.
** The FRC is derived from the damage weighted transmission data (Tdw-K) and compares the fading of the glass with that of 3mm clear float glass.
For more options refer to the Catalogue and Reference Guide – Section 12
The Good, Better, Best approach is a simplification of the complexity surrounding the selection of the
correct glass to provide the best design solution, and therefore other options, not listed on this sheet, are
available from Metro GlassTech. In addition other factors can affect the glass selection such as the risk
of thermal stress breakage and the requirements to comply with the NZ Building Code and NZS 4223.
www.metroglasstech.co.nz
April 2013

ACOUSTICS
(SOUND CONTROL)
Environmental noise is a key factor in modern housing design.
The source and frequency of the sound is important as glass products behave differently for low
to high pitch sounds.
Insulating Glass Units can provide a range of acoustic performance by using different glass types
and thicknesses.
GOOD
Float glass
Float glass
Solution:
GlassTech IGU
Using thick glass and glasses of
different thickness is GOOD for
sound control.
INNER
OUTER
BETTER
Laminated
glass
Float glass
Solution:
GlassTech Laminated IGU
Using standard PVB laminated
glass is BETTER as the interlayer
dampens sound vibration.
INNER
OUTER
BEST
Sound Stop ®
glass
Float glass
Solution:
GlassTech SoundStop IGU
Using special acoustic laminated
glass is BEST, especially if one
pane is thicker.
INNER
OUTER
www.metroglasstech.co.nz April 2013

PERFORMANCE DATA
Performance Data – The following tables compare the STC/Rw data and Perceived Sound Reduction
(PSR) for a range of IGUs. The PSR is a weighted sound reduction comparison that compares the glass
performance as a ratio compared to 3mm float glass.
GOOD
ACOUSTIC comparison
Float
glass
Float
glass
Type
Outer Glass
(mm)
Air Space
(mm)
Inner Glass
(mm)
STC* / Rw* PSR (%)**
- - 3 Float 28 0
The above data has been included for reference
OUTER
INNER
GlassTech® IGU
4 Float 6 4 Float 29 5
4 Float 12 4 Float 30 10
4 Float 12 5 Float 31 15
6 Float 12 6 Float 34 30
BETTER
ACOUSTIC comparison
Float
glass
Laminated
glass
Type
Outer Glass
(mm)
Air Space
(mm)
Inner Glass
(mm)
STC* / Rw* PSR (%)**
4 Float 6 6.38 Lam 34 30
6 Float 12 6.38 Lam 35 35
GlassTech
OUTER
INNER
Laminated IGU
BEST
ACOUSTIC comparison
Float
glass
SoundStop
glass
Type
Outer Glass
(mm)
Air Space
(mm)
Inner Glass
(mm)
STC* / Rw* PSR (%)**
6 Float 12 6.76 S 38 50
6 Float 12 8.76 S 39 52
GlassTech
6 Float 12 13 S 42 60
OUTER
INNER
SoundStop IGU
Note: S= SoundStop uses Acoustic Grade Interlayer
* STC = Sound Transmission Class.
* Rw = Weighted Sound Reduction Index.
** PSR = Perceived Sound Reduction is a weighted sound reduction comparison that compares the glass performance as a ratio compared to 3mm float glass.
S = SoundStop – is acoustic laminated glass.
Note: The STC/Rw and PSR data is based on the latest GANZ average data range and may vary from that published in the Metro GlassTech Catalogue and Reference Guide.
The Good, Better, Best approach is a simplification of the complexity surrounding the selection of the
correct glass to provide the best design solution, and therefore other options, not listed on this sheet, are
available from Metro GlassTech. In addition other factors can affect the glass selection such as the risk
of thermal stress breakage and the requirements to comply with the NZ Building Code and NZS 4223.
www.metroglasstech.co.nz April 2013

SAFETY (Human impact) April 2013
Safety for occupants is a key factor in modern housing design.
Glass is classified as a hazardous building material in the NZ Building Code Clause F2 and needs to be
either protected from human impact, strong enough to withstand impact without breaking, or break safe.
Human impact safety requirements are outlined in NZS 4223 Part 3:1999 and in most applications Safety
Glass is used.
When Insulating Glass Units are used the impact side is usually safety glass and this normally means
inner and outer panes.
GOOD
Solution:
GlassTech IGU
GlassTech IGUs that comply with NZS
4223 Part 3 are GOOD because they
comply with the NZ Building Code
requirements.
BETTER
Solution:
GlassTech Laminated IGU
GlassTech – Laminated IGUs are
BETTER as laminated glass is a Safety
Glass and will stay intact if broken.
BEST
Solution:
GlassTech Toughened IGU
GlassTech – Toughened IGUs are BEST
as toughened glass is a very hard to
break and if broken is a Safety Glass
as it breaks into small, relatively
harmless particles.
The Good, Better, Best approach is a simplification of the complexity surrounding the selection of the
correct glass to provide the best design solution, and therefore other options, not listed on this sheet, are
available from Metro GlassTech. In addition other factors can affect the glass selection such as the risk
of thermal stress breakage and the requirements to comply with the NZ Building Code and NZS 4223.
www.metroglasstech.co.nz

Security
Security for occupants and their property is key factor in modern housing design.
Normal glazing products provide limited security, but special laminated glasses are available
for a range of application from “smash and grab” through to bullet resistance.
When Insulating Glass Units are used, one or both panes can be a security glass.
GOOD
Toughened
glass
Toughened
glass
Solution:
GlassTech Toughened IGU
GlassTech Toughened IGUs are GOOD
as they are very hard to break, especially
if both panes are toughened.
INNER
OUTER
BETTER
Laminated
glass
INNER
Laminated
glass
OUTER
Solution:
GlassTech Laminated IGU
GlassTech Laminated IGUs are BETTER
as laminated glass provides better
penetration resistance.
Laminated glass can also be combined
with toughened glass on the outer or
inner pane.
BEST
Security
laminated
Toughened
glass
Solution:
GlassTech SuperSafelite IGU
GlassTech SuperSafelite IGUs are BEST
as they include security glass, such as
‘Anti Bandit’ or special security laminates
designed for forced entry protection.
INNER
OUTER
The Good, Better, Best approach is a simplification of the complexity surrounding the selection of the
correct glass to provide the best design solution, and therefore other options, not listed on this sheet, are
available from Metro GlassTech. In addition other factors can affect the glass selection such as the risk
of thermal stress breakage and the requirements to comply with the NZ Building Code and NZS 4223.
www.metroglasstech.co.nz April 2013

COMFORT
Comfort for occupants is a key factor for modern housing design.
When it is cold outside there are cold zones near windows know as “discomfort zones” and these
are more severe if the glazing is not insulated.
Insulating Glass Units improve the insulation and thus reduce the discomfort zones near windows
because the inner glass surface is much warmer than for single glazing.
GOOD
Clear glass
INNER
Clear glass
OUTER
Solution:
GlassTech IGU
Is GOOD because it meets the
minimum requirements for thermal
insulation for housing and small buildings
(NZS 4218) and keeps the inside glass
surface warmer than single glazing and
thus increasing the comfort zone.
BETTER
Low E glass
INNER
Clear glass
OUTER
Solution:
GlassTech Low E + IGU
Low E glass provides BETTER thermal
insulation as it traps heat inside by
reflecting long wave radiation and
keeping the inner glass warmer, further
increasing the comfort zone.
BEST
Low E glass
INNER
Argon gas
Clear glass
OUTER
Solution:
GlassTech Low E + and Argon + IGU
By combining Low E glass and argon gas
the BEST thermal insulation is achieved and
the inner glass is at it’s warmest, providing
the largest comfort zone.
Thermal spacers can be used in thermally
efficient frames to improve the total window
performance, thus increasing the comfort
zone.
PERFORMANCE DATA – Refer to Metro GlassTech Catalogue and
Reference Guide Section 11.2.3.
The Good, Better, Best approach is a simplification of the complexity surrounding the selection of the
correct glass to provide the best design solution, and therefore other options, not listed on this sheet, are
available from Metro GlassTech. In addition other factors can affect the glass selection such as the risk
of thermal stress breakage and the requirements to comply with the NZ Building Code and NZS 4223.
www.metroglasstech.co.nz
April 2013

COMFORT
One of the key benefits of using double glazing as insulation is the increase in comfort.
If you sit by a single glazed window/door when it is cold outside you can feel the cold and this is
known as the “Discomfort Zone”. By using Insulating Glass Units the discomfort zones can be
reduced even when it is -10ºC outside.
Single
glazing
Discomfort zones
External Temperatures -1ºC
External Temperatures -10ºC
Single
glazing
Single
glazing
Double
glazing
with
Low E
Double
glazing
The above diagram illustrates how discomfort Single zones occur near a window.
The example shows single glazed, double glazed and glazing
double glazed Low E windows with external temperatures
of -1ºC and -10ºC. At -10ºC, no discomfort zone is
distinguishable for double glazed Low E windows.
Double
glazing
with
Low E
Insulating Glass Units increase the inside glass temperature
to near room temperature and significantly improve the
comfort levels of the house.
The decisive factor in comfort is the temperature
difference between ambient air and the adjacent wall
and window surfaces. Most people find a room to be
particularly comfortable when the temperature differences
between wall (glass) and room air is not more than 5ºC
and between foot and head height is not more than 3ºC.
Double
glazing
www.metroglasstech.co.nz
April 2013

CHOOSE THE RIGHT GLASS FOR YOUR HOME
When building new, or renovating it is important to ensure you install the best glass combination into your windows and
doors. By combining different glass types and thicknesses, you can achieve high performing insulating glass units that will
ensure you maximise your design and comfort of your home.
Discuss the requirements of each room of the house with your window and door manufacturer and they will advise the best
combination to meet your needs. Concerns such as Heat Gain, Heat Loss, Condensation, Glare, Fading, Acoustics and Safety
and Security can all be addressed.
Heat Loss and Condensation
• Low E (Low Emissivity) glass improves insulation
• Argon is better than air for insulation
• Argon and Low E can be combined for higher performance
• Low E and Argon gas further reduce condensation
• The better the insulation the more comfortable the
environment
• The better the insulation the less condensation will occur
Heat Gain
• The lower the shading co-efficient (SC) the lower the heat gain
• Tinted glasses are better than clear glass.
• Insulating Glass Units help reduce heat gain
• Low E glass can help reduce heat gain
Glare
• The lower the visible light transmission (VLT) the lower the
glare
• Grey and bronze tints generally have lower light transmission
• Blue and green tints generally have higher light transmission
• Insulating Glass Units slightly reduce the light transmission
• Reflective glasses can cause internal glare at night
Fading
• The higher the UV elimination the lower the level of fading
• The lower the visible light the lower the fading
• The lower the heat gain the lower the fading
• Laminated glass helps reduce fading
• Tinted glass helps reduce fading
Acoustics
• Thicker glass will help reduce noise
• Laminated glass will help reduce noise
• Insulating Glass Units will help reduce noise
• Different glass thicknesses in an IGU will help reduce noise
Safety and Security
• 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 provide levels of security
Trust New Zealand’s leading
glass and glazing company
to provide the expertise and
Branches located
nationwide
quality your home deserves
Call us 0800 545 800
www.metroglasstech.co.nz