Published 20 May 2026 · Sash Window Draught Proofing
For homeowners in prime London districts like Chelsea, Kensington, and Westminster, the charm of a period property is often undermined by a persistent modern problem: traffic noise. Standard single-glazed sash windows provide almost no barrier against external sound pollution, but acoustic secondary glazing can deliver up to 50–54dB of noise reduction.
Why standard sash windows fail at noise control
Single-glazed sash windows have a Sound Transmission Class of around 27. Thin 4mm glass vibrates like a drum skin, and 1mm gaps around the sashes let noise bypass the glass entirely — which is why draught elimination is always the first step in any sash window refurbishment project.
The acoustic solution: 10.8mm Stadip Silence + 150mm air gap
Stadip Silence laminated glass uses a specialist PVB interlayer to dampen vibration at the critical frequencies where standard glass fails. Paired with a 100–150mm glass-to-glass air gap — vastly larger than the 16–20mm of sealed double glazing — the system decouples the panes and blocks low-frequency bus and HGV rumble.
Achieving a 50dB reduction
A busy London road produces 75–85dB. Acoustic secondary glazing brings that down to library-quiet 30dB indoors: 45–54dB reduction versus 32–35dB for standard double glazing. See our noise reduction service and the secondary glazing vs draught proofing comparison.
Heritage and conservation
Because secondary glazing is internal and fully reversible, it generally requires no planning permission — the preferred choice for Grade II listed properties in Kensington, Chelsea, Marylebone, Hampstead, Islington, Richmond and Dulwich. Complements our heritage window restoration and thermal efficiency work.
Cost and ROI
Draught proofing £150–£300 per window (~2 year ROI). Acoustic secondary glazing £400–£800 per window: up to 70% heat-loss reduction and up to 50dB noise cut. See the cost guide. All installations backed by a 10-year warranty. Call 0207 060 1573 for a free acoustic survey.