Four primary glass specifications are used in retrofit double glazing. Understanding the performance differences — not just the marketing claims — helps you match the specification to your actual needs and avoid paying for performance you don't require.
Standard Clear Float IGU
The baseline. Two panes of standard float glass (typically 4mm each) separated by a 12–16mm air cavity.
U-value: 2.7–2.9 W/m²K Rw acoustic rating: 28–32 SHGC: 0.7 (high solar heat transmission) Best for: Low-noise locations where budget is the primary concern. Meaningful thermal improvement over single pane, no acoustic premium.
Tinted Glass
One or both panes replace standard clear with body-tinted glass — grey, bronze, blue, or green. The tint is in the glass itself, not a coating.
U-value: Similar to clear float (~2.7–2.8 W/m²K) SHGC: Reduced to 0.5–0.6 depending on tint depth Best for: West and north-facing windows where solar heat gain reduction matters. Notably, tint reduces solar gain but not radiant heat loss — Low-E does both.
Low-E Glass
A metallic coating (typically silver-based) applied to one glass surface, facing the cavity. Reflects infrared radiation back to its source — inward in winter, outward in summer.
U-value (hard-coat): 1.8–2.0 W/m²K U-value (soft-coat + argon): 1.4–1.6 W/m²K SHGC: 0.3–0.5 depending on coating type Best for: Whole-home retrofit where thermal performance is the priority. Best value upgrade from standard glass — the cost premium pays back within a few winters.
Read more: Low-E glass explained
Acoustic Laminated Glass
One pane is a laminated unit — two glass plies bonded around a PVB (polyvinyl butyral) or SGP interlayer. The interlayer damps vibration and significantly improves sound insulation.
U-value: Similar to standard when combined with clear float pair (~2.7 W/m²K); combine with Low-E for thermal + acoustic. Rw: 38–44 depending on configuration Best for: Homes on tram routes, arterial roads, near rail, or under flight paths. A meaningful, audible difference in mid-frequency noise.
Read more: Best glass for noise reduction in Melbourne
Combination Specifications
The best-performing configurations combine Low-E with acoustic laminated glass:
- Acoustic laminated (inner pane) + Low-E (outer pane) + argon fill achieves Rw 40–44 and U-value 1.6–1.8 — thermal and acoustic performance without compromise.
This is the recommended specification for Melbourne inner-city homes with both noise and heating/cooling concerns.
Use the Glass Types comparison page for full specification tables. The Instant Estimate tool lets you price each option side by side.
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