What glazing should you use in Brisbane for a house?

The following is based on:

• Sensible amounts of glazing. In this instance glazing is 30% of the external wall area. See the house structure for an overview.
• Well-shaded glazing - this typically means minimal west/east glazing and overhangs to the north.
• Sound and other considerations are not ... considered.

Windows are a necessary evil - necessary because we like views and evil because they are expensive leaky and provide next-to-no insulation.

So the question becomes: how can I maintain views and limit heat entry into the house.

VLT and SHGC

We need a VLT of 40-80% for nice views. Say about 60% which looks pretty clear. In Brisbane we want a lowish SHGC say 0.50 too. This lets in half of the sun's heat. (If direct sun hits the windows in Summer you'll overheat: so if they are not shaded you're in trouble and would select a lower SHGC.) It allows some Winter warm up.

Single or Double Glazing, U Value

Single glazing was selected, with a low-e coating. This provides good performance in summer, as the low-e coating reduces radiant solar gains. It is cheaper than double glazing. Double glazing has similiar VLT/SHGC performance. For example, GJames DGU EnergyTechClear (Low E) has SHGC 0.61 and VLT 73% while SGU Solect Sttel (Low E) has SHGC 0.59 and VLT 68%. So double glazing is not much better on the SHGC/VLT front.

Single glazing U-value is about U3.6. Double glazing U-value is about U2.0. So it's better

• Glass and frame: U5.5
• Glass: Low-E on inside surface, single glazed.
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Format

Casement windows were selected