Double Glazing & Energy-Efficient Glass

People often ask for double glazing when what they want is quiet. The two goals need different glass, and getting this wrong is an expensive way to be disappointed.

• For heat, use an insulated glass unit. Two panes with a sealed, usually argon-filled cavity and a Low-E coating. The cavity does the insulating; the coating reflects radiant heat back where it came from.
• For traffic and aircraft noise, use laminated glass. An acoustic interlayer between two panes damps sound vibration far more effectively than an air gap of the same overall thickness. Two panes of equal thickness with a small cavity can actually resonate and perform poorly at particular frequencies.
• For both, combine them. An IGU with a laminated acoustic inner pane and asymmetric pane thicknesses is the answer for a main road with cold winters.
• Check the frame and the seals first. A gappy old aluminium frame leaks both heat and noise. The best glass in the world will not fix a draught you can feel with your hand.

In many cases the existing frame can take a thicker insulated unit, which avoids the cost and disruption of replacing whole windows.

• Condensation. The inner pane stays much closer to room temperature, so the water in the air stops condensing on it. This is the change people notice fastest.
• Comfort near the window. Sitting beside a single-glazed window in winter feels cold because you are radiating heat to it. That stops.
• Compliance. New builds and major renovations in NSW have energy requirements to satisfy, and the glazing specification is a large part of meeting them.
• What it won't do. Fix a west-facing room with no external shading. Glass helps, but a pergola, an awning or an external blind stops the sun before it arrives, which is always more effective.