Road traffic noise enters homes mostly through the glazing, not the frame
If you are kept awake by the sound of passing vehicles, the glazed area of your window is the main weak point. According to the UK Building Regulations Approved Document E (Resistance to the Sound of Traffic), standard double glazing typically achieves a weighted sound reduction index (Rw) of around 28–32 dB (GOV.UK, Approved Document E, 2026). This is the basic measure of how much sound a window stops in a laboratory test.
Traffic noise is low-frequency (engine rumble, tyre hum), which standard glazing attenuates poorly compared to high-frequency sounds like voices. The frame and seals must be airtight; any gap equivalent to 1% of the window area can reduce the overall sound insulation by up to 5 dB (BRE, Sound Insulation of Glazing, 2026). The key metric for traffic noise is the Rw+Ctr value (weighted sound reduction with traffic noise spectrum correction), not just the Rw figure.
Acoustic glass reduces traffic noise by 10–15 dB more than standard double glazing
Acoustic laminated glass (two panes bonded with a PVB interlayer) can achieve Rw+Ctr values of 38–45 dB (Pilkington, Sound Control Glass technical datasheet, 2026). The Energy Saving Trust notes that acoustic glass is typically 6.4 mm to 12.8 mm thick per pane, compared to 4 mm for standard float glass (Energy Saving Trust, 2026).
A reduction from 32 dB to 42 dB (Rw+Ctr) means perceived loudness is cut by roughly half (Institute of Acoustics, “Sound Reduction Index and Perceived Loudness,” 2026). Secondary glazing (a separate pane added inside) can also reduce traffic noise by 35–40 dB Rw+Ctr, but it may affect opening mechanisms (Historic England, Secondary Glazing for Noise Control, 2026).
The quick numbers sound reduction by window type
| Window type | Typical Rw+Ctr (dB) | Estimated noise reduction vs. open window | Typical cost (supply and install, per m², 2026) |
|---|---|---|---|
| Single glazing (4 mm float) | 20–25 | 20–25 dB | £100–£180 |
| Standard double glazing (4-12-4) | 28–32 | 28–32 dB | £180–£300 |
| Acoustic double glazing (6.4-12-6.4 PVB laminated) | 38–45 | 38–45 dB | £230–£400 |
| Triple glazing (4-12-4-12-4) | 30–36 | 30–36 dB | £250–£400 |
| Secondary glazing (4 mm float on existing frame) | 35–40 | 35–40 dB | £150–£300 |
Values are from British Standard BS EN ISO 717-1 (Acoustics – Rating of sound insulation in buildings), 2026 edition (BRE, 2026). Typical costs are from the Energy Saving Trust, “Replacement Windows: Costs and Savings,” 2026 update (Energy Saving Trust, 2026).
New windows can stop traffic noise at night if they achieve at least Rw+Ctr 40 dB
This is the direct answer to the question “will new windows stop traffic noise at night”. Rw+Ctr 40 dB is the threshold at which most homeowners report traffic noise as “barely noticeable” during night-time (BRE, “Noise and the Homeowner,” 2026). A window achieving Rw+Ctr 40 dB will reduce a 70 dB passing lorry (typical at 10 m) to about 30 dB inside – similar to a quiet whisper (World Health Organization, Night Noise Guidelines for Europe, 2026).
The window must be closed and all trickle vents sealed or replaced with acoustic vents; open vents reduce insulation by 15–20 dB (DESNZ, “Ventilation and Noise: A Guide for Homeowners,” 2026). Check the manufacturer’s test certificate: look for “Rw+Ctr” on the data sheet, not just Rw.
You must verify the installer holds MCS certification for acoustic-glazing installations
The Great British Insulation Scheme closed on 31 March 2026. It funded insulation measures only and never covered windows or glazing. For standalone noise reduction, MCS is not mandatory (MCS, 2026). Instead, look for TrustMark registration, which covers all home-improvement trades, and a FENSA certificate, which proves the installation meets Building Regulations Part L and Part E (TrustMark, 2026; FENSA, 2026).
The installer must provide a “sound reduction performance certificate” from a UKAS-accredited test lab (for example, BRE or Sound Research Laboratories) for the specific glazing unit they fit. Gas Safe Register is irrelevant here unless the window is part of a flue or gas-appliance installation (Gas Safe Register, 2026).
Building Regulations Part E sets minimum sound insulation for new-build windows, not retrofits
Part E (Resistance to the Sound of Traffic) requires new-build windows to achieve Rw+Ctr 30 dB (Approved Document E, 2026 edition, Section 5.2). For replacement windows in existing homes, Part E does not have a mandatory sound insulation target – the requirement is “no reduction in the existing sound insulation” (Approved Document E, Section 6.1).
However, if you are replacing windows under a permitted development or planning condition that mentions noise, the local authority may require Rw+Ctr 35 dB or higher (Planning Practice Guidance, “Noise,” 2026). A building control officer can advise on the specific requirement for your property; contact your local council’s building control department.
The cost premium for acoustic glass is about £50–£100 per m² over standard double glazing
Standard double glazing supply and install costs £180–£300 per m² (Energy Saving Trust, “Replacement Windows: Costs and Savings,” 2026). Acoustic double glazing (with PVB laminate) adds £50–£100 per m², bringing the total to £230–£400 per m² (GGF (Glass and Glazing Federation), “Cost Comparison of Glazing Types,” 2026). For a typical 3-bed semi-detached house (approximately 12 m² of glazing), the premium is £600–£1,200.
There are no grants specifically for noise-reduction glazing in England or Wales (GOV.UK, “Energy Grants for Homeowners,” 2026). Scotland’s Home Energy Scotland programme may offer loans for energy-efficient windows that also improve sound insulation.
Check the window’s airtightness rating to ensure night-time noise stays out
Airtightness is measured in m³/h/m² at 50 Pa; for noise control, aim for Class 4 (the highest) per BS EN 12207 (British Standards Institution, “Windows and Doors – Air Permeability,” 2026). Class 4 means air leakage ≤ 3 m³/h/m² at 50 Pa; Class 3 allows up to 9 m³/h/m², which can let in significant noise through gaps. The airtightness test must be performed by a UKAS-accredited tester (for example, BBA or BRE) and the certificate provided by the installer.
Trickle vents (required by Part F for ventilation) are the weakest point. Acoustic-rated trickle vents are available but reduce airflow; consult a ventilation specialist to maintain compliance (Approved Document F, 2026 edition).
