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The FAQs above cover the quick questions. These deeper articles, services and area pages answer the follow-up questions homeowners ask once they're seriously specifying secondary glazing for a London property.
Long-form benefits guide expanding every short answer in the FAQ above.
Side-by-side comparison that resolves the most common "which is better?" FAQ.
A detailed walkthrough of the planning rules behind the "do I need permission?" FAQ.
How decoupling, mass and cavity depth produce the dB figures quoted in our FAQ answers.
The survey behind every property-specific recommendation we make in the FAQ.
Real cost ranges to pair with the "how much does it cost?" FAQ.
Authoritative sources supporting the information on this page.
Sets the recommended internal noise levels for bedrooms and living rooms used to judge how much glazing performance a home needs.
The statutory guidance on sound insulation in dwellings in England.
Defines the Rw and Rw+Ctr ratings used to compare the acoustic performance of glazing systems.
Describes how the sound insulation of glass types, including acoustic laminates, is characterised.
Evidence-based guideline levels for road, rail and aircraft noise and their links to sleep disturbance and health.
Much of London is Victorian, Georgian or Edwardian housing, often in conservation areas where replacing original sash windows is restricted. Secondary glazing sits discreetly inside the existing window, keeping the outside appearance unchanged while adding a second sealed layer with a wide air gap.
That air gap is what makes the difference for noise. Double glazing typically has a gap of a few millimetres; secondary glazing can create a much larger cavity, which is far more effective against traffic, rail and aircraft noise.
Noise reduction of up to 54dB is achievable in suitable configurations; actual results depend on the existing window, the surrounding wall and the quality of installation.
