Updated, 22.09.26

The Greater London Authority is consulting on a new Draft London Plan that will guide how London grows and develops over the next 20 to 25 years. The statutory consultation closes at 5pm on 15 October 2026 and is expected to be followed by an Examination in Public in 2027.

The Soundproof Windows submitted technical representations on two policies: HN8 Housing Design and GHR4 Heat Risk. Our comments were deliberately narrow and focused on a practical design question: how can homes exposed to environmental noise provide satisfactory internal acoustic conditions, adequate ventilation and protection from overheating at the same time?

View the official Draft London Plan consultation

Policy HN8 recognises that external noise and pollution can affect the practicality of openable windows, while GHR4 prioritises passive measures for managing heat risk, including openable windows and cross-ventilation.

Our representation highlighted the practical interface between these policies. A dwelling may demonstrate satisfactory internal acoustic conditions with windows closed while its overheating strategy separately relies on those same windows being opened for extended periods. Both strategies can therefore appear satisfactory independently without showing that the home will provide satisfactory conditions during realistic occupation.

Our submission asked that this interaction is made explicit in the Plan or its supporting guidance.

Acoustic performance should be considered at the level of the complete façade. A laboratory Rw or Rw + Ctr value for an insulating glass unit does not establish the acoustic performance of an installed window or finished building façade.

Internal conditions can also depend on the window system, opening configuration, seals, air leakage, ventilators, installation junctions, wall construction and other transmission paths.

Where the planning objective is an internal acoustic condition, the relevant design question is whether the completed façade and ventilation strategy can achieve that outcome in use.

Openable windows are valuable for daylight, amenity, purge ventilation and passive cooling. In a noisy environment, however, prolonged window opening may significantly alter internal acoustic conditions.

Our representation therefore suggested that where environmental noise constrains the practical use of openable windows, acoustic design, ventilation and overheating should be assessed together rather than as independent compliance exercises.

This integrated approach is consistent with the Institute of Acoustics and Association of Noise Consultants’ Acoustics, Ventilation and Overheating Residential Design Guide.

View the IOA/ANC Acoustics, Ventilation and Overheating Residential Design Guide

Our HN8 representation also referred to recent UK aviation-noise research as an example of why environmental noise should be considered carefully at residential-design stage.

The Civil Aviation Authority published the Aviation Noise Attitudes Survey 2023–2024 (ANAS) in June 2026. The study examines the relationship between long-term exposure to aviation noise and annoyance around UK airports. The Department for Transport and CAA also published the subjective phase of the Aviation Night Noise Effects (ANNE) study, examining associations between night-time aircraft-noise exposure, sleep disturbance and annoyance.

These studies concern aviation and their numerical findings should not simply be transferred to road, rail or entertainment noise. Their broader relevance is that the impact of environmental noise depends not only on an external average exposure metric, but also on when noise occurs, how individual events are experienced and the conditions inside the home.

CAA Aviation Noise Attitudes Survey 2023–2024

CAA Aviation Night Noise Effects Study

We proposed the following principle for consideration in the final Plan or supporting guidance:

“Where environmental noise may constrain the practical use of openable windows, residential development should demonstrate that satisfactory internal acoustic conditions, adequate ventilation and acceptable summertime thermal conditions can be achieved together under realistic operating conditions.”

We also suggested that assessment should consider the complete façade, including ventilation openings and relevant transmission paths, rather than relying solely on the laboratory acoustic performance of glazing.

This wording deliberately avoids prescribing a particular technical solution. Depending on the site, appropriate responses could include site layout, building orientation, dual-aspect design, quieter façades, room arrangement, source control, façade design, alternative ventilation strategies or other measures.

As part of both representations, we confirmed that we would be willing to contribute to the future Examination in Public if invited by the Inspector. Any contribution would be limited to our specialist area: the practical interaction between environmental noise, whole-façade acoustic performance, ventilation and overheating in residential development.

This is a technically interdependent issue and one that can be difficult to describe fully through separate acoustic and overheating calculations alone.