Single vs Double Glazing: When to Upgrade

The question of single versus double glazing comes up on almost every residential job. Here's a straightforward comparison to help you advise your customers.

Thermal Performance A single 6mm clear pane has a U-value of about 5.8 W/m²K. A standard double glazed unit (6/12/6 with air fill) drops this to about 2.7 W/m²K — more than halving the heat transfer. Add Low-E coating and argon gas fill, and you can achieve U-values below 1.5 W/m²K.

Noise Reduction Single glazing offers minimal noise insulation (about 25 dB reduction). Standard double glazing improves this to about 30–32 dB. For maximum noise reduction, use different glass thicknesses on each pane (e.g. 6/12/10) to prevent resonance at the same frequency.

Condensation Condensation forms on single glazed windows when the interior glass surface temperature drops below the dew point. Double glazing dramatically reduces condensation by keeping the inner pane warmer.

Cost Comparison Double glazed units cost roughly 2–3 times more than equivalent single glazed panels. However, the price gap has narrowed significantly over the past decade. When you factor in reduced energy bills, improved comfort, and increased property value, double glazing is almost always worth the investment for permanent installations.

When Single Glazing Still Makes Sense • Temporary structures or sheds • Internal partitions and shopfronts where thermal performance isn't critical • Budget-constrained projects where the opening size is small • Heritage buildings where the original window profile must be maintained

Weight Consideration Double glazed units weigh approximately double the equivalent single pane. A 6/12/6 IGU weighs about 30 kg/m² compared to 15 kg/m² for a single 6mm pane. This affects hardware selection — hinges, tracks, and operators must be rated for the heavier weight.