Double-glazed uPVC windows are the right answer for two specific problems: real road noise (highway-facing rooms, near commercial areas, near temples or schools) and real heat gain (west-facing or south-facing rooms with direct afternoon sun). For ordinary rooms in quiet residential areas, single glazing is usually fine and double-glazing is overspec. Glassterr manufactures double-glazed uPVC windows at our Pannimadai factory using sealed glass units (two panes, argon or air gap, edge spacer with desiccant). The performance is real and measurable — typical noise reduction of 8-12 dB over single glazing, typical heat-gain reduction of 30-50%. The cost premium is real too — about 40-60% more than single glazing.
A double-glazed (DGU) window unit consists of two glass panes separated by a sealed gap, with a perimeter spacer that contains desiccant and is sealed with butyl and silicone. The gap is filled with air or argon gas (argon performs better but costs more). The two panes can have different glass types — for example 6mm laminated outer + 4mm toughened inner for noise reduction, or low-E coating on the inner pane for heat reduction. The whole unit fits into the same uPVC profile groove as single glazing, just with deeper-section profile to accommodate the thicker DGU. The frame seals around the unit with butyl and a structural setting block.
Typically 8-12 dB over single glazing — which sounds modest but is significant. dB is logarithmic, so 10 dB reduction halves the perceived loudness. A bedroom facing a noisy road that's 'too loud to sleep' with single glazing usually becomes 'noticeable but tolerable' with double. For extreme noise, triple glazing or laminated DGU gives more reduction.
In west-facing rooms with afternoon sun, yes — the AC heat-load can drop 25-40% which translates to lower electricity bills. The payback period varies from 3-7 years depending on AC usage. In north-facing or shaded rooms, double-glazing's heat benefit is marginal and probably not worth the cost.
Yes — the sealed cavity is hermetically sealed at manufacture, with desiccant in the spacer to absorb any minor moisture. Quality DGUs have 10-15 year sealed-cavity warranties. The seal can fail eventually (typically after 20+ years), at which point you'll see fogging between the panes — that's the cue to replace the glass unit, not the whole window.
Roughly 40-60% more than single-glazed for the same window. For a 4ft × 4ft sliding window, expect ₹25,000-40,000 double-glazed vs ₹15,000-25,000 single-glazed. The premium is mostly the glass itself; the frame is slightly different too.
Just specific rooms is usually the right call. Bedrooms on noisy roads, west-facing AC rooms, study rooms — these benefit most. Kitchens, bathrooms, internal-facing rooms — usually overkill. We can spec your house room-by-room rather than uniformly.
Related guides covering this topic from other angles — different products, applications, or contexts.
Tell us which rooms have noise or heat problems — we'll spec double-glazing where it pays off.