How much does secondary glazing cost in London?

Secondary glazing in London typically costs between £300-£600 per window for professional installation. Factors affecting price include window size, glazing type, and frame material. We offer free surveys and quotes.

Does secondary glazing reduce noise effectively?

Yes, secondary glazing can reduce noise by up to 80% (45dB). It's particularly effective for traffic noise, aircraft noise, and busy urban environments. The air gap between windows is key to acoustic performance.

Can secondary glazing be installed in listed buildings?

Yes, secondary glazing is often the preferred solution for listed buildings as it preserves original windows. It typically doesn't require planning permission as it's a reversible internal alteration.

How long does secondary glazing installation take?

Professional installation typically takes 30-60 minutes per window. Most homes can be fully fitted within a single day with minimal disruption to your daily routine.

Suitable acoustic secondary glazing can achieve up to 54dB reduction; typical double glazing is often around 25–30dB.

Secondary Glazing vs Double Glazing for Listed Buildings: Which Wins on Noise, Cost and Consent?

For a listed building, the best window decision is not simply the one with the lowest U-value. Noise, consent, cost, original fabric and reversibility all matter.

At a glance

Measure	Secondary glazing	Typical double glazing
Noise	Up to 54dB / up to 80% quieter	Typically around 25–30dB
Cost	From £675 small casement, installed incl. VAT	Varies; replacement may include joinery and consent work
Consent	Internal and reversible; typically no Listed Building Consent, subject to confirmation	Replacement in listed buildings usually requires consent
Thermal	U-value 5.0 to 1.8 W/m²K; up to 64% less heat loss	Can be thermally strong, but depends on the complete replacement specification
Reversibility	Original windows preserved fully	Original windows are removed or altered

Noise: why the wider cavity matters

Secondary glazing creates an independent internal barrier behind the original window. With 10.8mm acoustic laminated glass and careful sealing, suitable installations can reduce noise by up to 54dB, described as up to 80% quieter. Typical double glazing can improve noise, but a standard replacement unit is not automatically an acoustic specification.

Cost and disruption

Guide prices for installed secondary glazing including VAT are £675 for a small casement, £1,220 for a Victorian sash and £2,565 for a Georgian bay. A replacement quote may include new frames, making good, decorating and consent-related professional work. Compare like with like in our real prices guide and use the calculator for an initial estimate.

Consent and reversibility

Internal secondary glazing is usually a lower-impact intervention because the external window stays in place. Listed building consent is not automatically required for every internal system, however. Check with the local authority or conservation officer before work. Our planning permission guide explains what to document.

Thermal performance

A suitable secondary specification can improve a window from U-value 5.0 toward 1.8 W/m²K, representing up to 64% less heat loss through the window area. Double glazing can also be thermally effective, but the decision for a listed home must include the effect on original fabric and heritage value.

Honest limitations

In a non-listed home undergoing a full renovation, double glazing may be the better choice. It can combine frame replacement, ventilation and thermal upgrades in one project. We serve listed and conservation properties, and being honest about that distinction is deliberate.

Frequently asked questions

Which is quieter?

Suitable acoustic secondary glazing can achieve up to 54dB reduction; a typical double-glazed unit is often around 25–30dB. The actual result depends on the room and noise path.

Which is more reversible?

Secondary glazing preserves the original windows fully and can be removed later. Replacement windows alter or remove the originals.

Does secondary glazing need consent?

It is internal and typically lower impact, but listed building consent and local conservation guidance must be checked for the specific property.