70-85 dB
75-100 dB
80-120 dB
60-80 dB
Sound travels through windows via two mechanisms: directly through the glass itself, and through gaps and seals around the frame. Secondary glazing addresses both issues by adding a second barrier of glass and creating a substantial air gap that disrupts sound transmission - particularly effective for draughty sash windows.
For maximum acoustic performance, we use laminated acoustic glass in our secondary glazing. This specialist glass contains a sound-absorbing interlayer that dampens vibrations, preventing them from passing through to your living space. Combined with the air gap, this can reduce noise levels by up to 45-50 decibels.
Every 10 dB reduction represents a halving of perceived noise. A 45 dB reduction makes busy traffic sound like a quiet residential street.
💡 Professional Installation Tip: Maximum noise reduction requires precise fitting and proper sealing. Our acoustic secondary glazing installers achieve up to 80% noise reduction with specialist acoustic glass and expert installation techniques.
Two sheets of glass bonded with an acoustic PVB interlayer. Our standard choice for moderate noise reduction.
Heavy-duty acoustic glass for severe noise problems, combining multiple glass thicknesses.
For optimal acoustic performance, the air gap between your existing window and the secondary glazing should be at least 100mm, with 150-200mm being ideal. This larger gap disrupts the sound waves more effectively than the narrow cavity in standard double glazing. Fixed panels provide the best acoustic seal for windows that don't need to open.
Using different glass thicknesses in the original window and secondary glazing also helps, as each thickness resonates at a different frequency, providing broader spectrum noise reduction. This approach also delivers excellent thermal insulation benefits.
We have extensive experience helping London residents affected by noise from various sources:
Properties in West London affected by aircraft noise, including Hounslow, Richmond, and Twickenham.
Homes near overground lines, including properties in Clapham, Brixton, and along the North London Line.
Properties on arterial routes like the A40, A4, South Circular, and North Circular roads.
Homes and flats in busy areas including Shoreditch, Soho, Camden, and around railway stations.
Many period properties in noisy areas are in conservation areas or are listed buildings where replacement windows are not permitted. Secondary glazing provides the only viable solution for noise reduction while preserving original Victorian, Georgian, and Edwardian windows.
Secondary glazing can reduce external noise by up to 80% (45-50 decibels). Using acoustic laminated glass with a 100-150mm air gap provides maximum sound insulation.
We recommend 6.8mm or thicker acoustic laminated glass for optimal noise reduction. For severe noise problems, 10.8mm or 12.8mm acoustic glass provides even better performance.