Your Home Climate
Performance · The problem library

Why is the street noise so audible, and what genuinely reduces it?

Recently reviewed·Reviewed June 2026, next review December 2026

Sound enters a home through whatever gap or thin surface is closest to the noise source. Old single-glazed sashes are often the loudest, but letterboxes, air bricks and unsealed gaps can rival them. Acoustic performance scales with mass and airtightness, which is why secondary glazing performs better than many people expect.

Editorial confidence
Confident. Backed by a strong source or several weaker ones in agreement.
Evidence status
Recently reviewed · reviewed June 2026 · next review December 2026
Monitoring
Every six months, plus whenever Part E acoustic guidance for dwellings or secondary-glazing acoustic data is updated.
Evidence drawn fromBuilding standards: CIBSEProfessional bodies: FETA, EST

You may not need to read the rest of this page

You probably already have enough to act if:

  • Traffic is audible through closed windows at night
  • You have older windows and have not yet sealed gaps or costed secondary glazing
Open the windows guide

This is probably the wrong page for you if:

  • The noise originates inside your home
  • You already have acoustic-rated triple glazing in the affected rooms

Typical secondary glazing acoustic gain (wide cavity)

+10 dB over original single glazing with 100mm+ air gap

Source: Chartered Institution of Building Services Engineers · CIBSE acoustic notes report 8-12 dB improvement for secondary glazing with cavities of 100mm or greater.

Who this advice is for

Applies to

  • Older single-glazed windows facing busy streets
  • Letterboxes and unsealed gaps that transmit sound as well as heat
  • Front-facing rooms where the noise source is constant

Not intended for

  • Noise originating inside the dwelling
  • Vibration-borne noise that needs structural acoustic isolation

What it usually looks like

These are the symptoms readers describe most often. None of them alone is diagnostic, but together they build a picture.

  • Traffic audible at night through closed windows
  • Conversation outside legible inside
  • Older single-glazed windows worst affected
  • Front rooms noticeably louder than rear

Most common in: Victorian terrace · Edwardian semi-detached

Before you buy anything

Watch the house respond as you scroll.

These checks are listed in the order we would work through them. The illustration on the left changes with each one, so you can see what each check is actually addressing before deciding whether it is worth doing.

The source is loud, the path is direct, and the room receives all of it.

01

Seal the obvious gaps first

Letterboxes, keyholes, gaps around frames and unsealed pipework leak sound as well as heat. Closing them is cheap and immediately audible.

02

Add heavy curtains or interlined blinds

Mass absorbs sound. Heavy fabric over a window will reduce perceived noise even without changing the glass.

03

Look at secondary glazing before replacement

Secondary glazing with a wide air gap of 100mm or more outperforms most replacement double glazing for sound, while keeping the original window.

04

Inspect air bricks and vents

Air bricks transmit sound directly. Acoustic vents preserve airflow while cutting noise significantly.

05

Consider room layout if the noise source is unavoidable

Moving the bedroom to the back of the house can sometimes solve a noise problem more reliably than expensive fabric work.

What we recommend, and why

Every recommendation explains why it comes first, the evidence behind it, how confident we are, and when it would not apply.

01

Seal the obvious gaps before any acoustic work

Why this comes first

Letterboxes, keyholes, gaps around frames and unsealed pipework leak sound as freely as they leak heat. Closing them is cheap and the improvement is immediately audible.

Evidence

CIBSE acoustic guidance and EST draught-proofing notes both list small-gap sealing as the first stage of any residential noise strategy.

CIBSE · EST

Confidence

High confidence. Multiple independent sources agree on the direction and the order.

Exceptions
  • Properties where gap sealing would compromise required ventilation
Next step
See the windows guide
02

Cost secondary glazing before replacement for noise

Why this comes first

Secondary glazing with a wide cavity outperforms most replacement double glazing for sound, and it keeps the original window in place. For listed and conservation properties it is often the only acceptable answer.

Evidence

CIBSE acoustic notes and FETA application guidance both report secondary glazing outperforming standard replacement units for acoustic gain.

CIBSE · FETA

Confidence

Reasonable confidence.

Exceptions
  • Properties already triple-glazed with acoustic interlayers
Next step
Open the windows guide

Real homes that faced this

Publicly documented UK projects that ran into the same problem and reported what happened.

We did not run these projects. Each links back to the original publisher so you can read the figures in context and judge for yourself what carries over to your home.

Evidence behind this page

Every recommendation on this page is traceable to its source. Click a publication to read the original.

Products that may help

Only consider these once the checks above have been ruled out. A product fitted into the wrong cause is rarely satisfying.

House Summary

The cheapest answer to street noise getting in is usually the one that addresses the cause rather than the symptom. The list above is in the order we would work through it, because the checks at the top tend to rule out the most expensive mistakes further down.

Related decisions
Next Best Step

Insulation; the upgrade that decides everything

Take the next step