The importance of considering the total window/glass combination

Glass Terminology

SOLAR CONTROL

• SHGCSolar Heat Gain Coefficient

– How well a product blocks heat caused by the sun.– Expressed as a % of solar heat gain transmitted.

• SCShading coefficient

Similar to SHGC, not commonly used.

THERMAL INSULATION• U value

– The rate of heat loss– Smaller the number the better

VISIBLE LIGHT• VT

– Expressed as a % of visible light transmitted.

DOUBLE GLAZING• IGU

– Insulating glass unit. – The hermetically sealed glazing unit, normally comprising

of 2 sheets of glass and a spacer bar.

3mm Clear Glass

• Standard 3mm glass• Basis of all other glass

calculations and comparisons.

U value = 4.53

SHGC = 0.8787% of solar heat gain transmitted

SC = 1

3mm Bronze Glass (Toned)

• Traditional toned glassU value = 4.81

SHGC = 0.73

73% of solar heat gain transmitted

VT = 0.63

63% of visible light transmitted

5mm Spectrally Selective Glass (SST)

• Spectrally selective toned glass

• Lower solar heat gain

• High light transmission

U value = 4.8

SHGC = 0.66

66% of solar heat gain transmitted

VT = 0.63

63% of visible light transmitted

SC = .57

3/12/3 Clear Double Glazing (D3123)

• Cuts heat loss in ½ due to the insulating air space between the glass layers.

• Allows transmission of high % of visible light and high solar heat gain.

U value 2.43

VT = 0.81

81% of visible light transmitted

SHGC = .77

77% of solar heat gain transmitted

SC = .891

Low E Low Transmittance (DGET)

• Best used on position 2 of a IGU

• Spectrally selective

• Use to reject heat

• Not generally available, additional cost involved.

U value 2.2

SHGC = 0.39

39% of solar heat gain transmitted

SC = .45

VT = 0.70

70% of visible light transmitted

Low E Argon Filled (DLEA)

• Best used with Low e on position 2 of a IGU

• Spectrally selective

• Use to reject heat

• Not generally available, additional cost involved.

U value 1.5

SHGC = 0.39

39% of solar heat gain transmitted

SC = .45

VT = 0.80

80% of visible light transmitted

Low E ( High Transmittance)

• Used on position 3 of a IGU

• Enhances the insulating value of a IGU

• Ideal for a heating environment to retain internal heat.

U value 1.92

SHGC = 0.71

71% of solar heat gain transmitted

SC = .82

VT = 0.75

75% of visible light transmitted

Window Terminology

• Window frame

Generic Aluminium (ALSTD)

Aluminium Improved (ALIMP)

Thermally Broken (ALBRK)

Timber (TIM)

PVC

Steel

Generic aluminium windows

• Readily conducts heat.• Increases the overall U

factor of the window.• In cold climates

condensation can form on the inside surfaces.

Thermally Broken

• Thermally broken by splitting the frame into interior and exterior pieces.

• Frame U value = 3.8 compared to Generic Aluminium window of U = 12.7

Aluminium Improved Frame

• Slender frame, reducing the overall frame area.

• Built into a timber reveal breaking the heat loss path from inside to outside

Timber Windows

• Energy efficient frame

• Requires good sealing system to minimise air leakage

• Maintenance

• A&L Windows• Canterbury Windows• Efficient Windows Collaborative• Pilkington• SEAV

AGGA would like to thank the following:

For further information on energy efficient glass contact

AGGA on 03 9853 3464

agga@bigpond.com.au

03 9853 3464

agga@bigpond.com.au