Residential Conversion Noise Assessment in Totton, Southampton

This residential conversion noise assessment case study relates to a mixed-use building in Totton, Southampton, where Polaris Acoustics was instructed to assess the acoustic suitability of converting upper-floor space into new residential studio flats.

The site was located within a town centre setting, with road traffic noise, nearby commercial uses, rear service and parking activity, and existing kitchen extract plant all requiring consideration. The assessment was prepared to support the planning application and demonstrate that suitable internal noise levels could be achieved for future occupants.

Following submission of the noise assessment, the scheme received consent from the local planning authority with no further noise comments and no noise-related planning conditions.

Project Summary

Item	Detail
Project type	Residential conversion / mixed-use development
Location	Totton, Southampton, Hampshire
Planning context	Upper-floor residential conversion above retained commercial use
Main acoustic risk	Introducing new homes into an existing road traffic and commercial noise environment
Key noise sources	Road traffic, commercial activity, kitchen extract plant, rear service area, car parking and future M&E plant
Standards and guidance	BS 8233:2014, ProPG, BS 4142:2014+A1:2019, Approved Document F, Approved Document O and the AVO Guide
Acoustic input	Noise survey, façade assessment, glazing strategy, ventilation review, overheating considerations and plant noise limits
Outcome	Consent granted with no further noise comments or noise-related conditions

The Brief

Polaris Acoustics was appointed to provide a planning-stage noise assessment for a proposed residential conversion in Totton, Southampton.

The proposed scheme involved the refurbishment and change of use of the upper floors of an existing mixed-use building to provide new residential studio flats. Commercial use was to be retained at ground floor level.

The key requirement was to demonstrate that the proposed residential accommodation would provide acceptable living conditions for future occupants, having regard to the existing mixed-use acoustic environment. This was particularly important given the site’s town centre context in Totton, where upper-floor residential use would sit alongside road traffic, rear service and parking activity, neighbouring commercial premises and existing plant associated with the previous ground floor use.

The assessment was therefore prepared with reference to national planning policy and guidance, including the NPPF, Noise Policy Statement for England and Planning Practice Guidance on Noise, together with the relevant New Forest District Local Plan objectives for safe, healthy and well-designed development. In particular, the assessment considered how the scheme would avoid or minimise adverse noise effects and protect residential amenity, consistent with the Local Plan’s approach to managing environmental risks and securing appropriate design quality. This included reviewing the road-facing façade, rear service area, nearby commercial uses and existing kitchen extract plant, before setting out a proportionate acoustic design strategy for glazing, ventilation, overheating and future plant noise control.

Site Context

Totton is a busy Hampshire town on the western side of Southampton. Its town centre includes a typical mix of shops, food premises, offices, residential properties, local roads, parking areas and rear service access routes.

In this type of location, the acoustic environment is rarely dominated by one source. Road traffic may control the design of the front façade, while rear elevations can be affected by vehicle movements, servicing, refuse activity, fixed plant and commercial operations.

For this site, the road-facing elevation was the most exposed part of the proposed development. However, the rear service and parking area also needed to be reviewed because this type of space can be a source of intermittent local noise, particularly where residential uses are introduced into existing commercial areas.

The assessment also considered wider environmental noise sources, including distant rail noise from the South Western Main Line, although road traffic and local commercial activity were the main design considerations.

Acoustic Challenges

The project raised several common issues for residential conversion schemes in Totton, Southampton and similar Hampshire town centre locations.

First, the proposed flats would be exposed to road traffic noise. This required an assessment of both average internal noise levels and night-time maximum noise events, as individual vehicle pass-bys can be relevant to sleep disturbance.

Second, the relationship between the proposed residential units and the retained commercial use needed to be considered. Residential accommodation above or close to commercial premises can be acceptable, but the design must avoid obvious future conflict.

Third, existing kitchen extract plant associated with the previous ground floor use was identified as a relevant noise source. Kitchen extract fans can generate steady, tonal or intermittent noise and are a common issue on mixed-use sites, particularly where flats are located nearby.

Fourth, the assessment needed to address ventilation and overheating. Acoustic glazing only works properly when windows are closed. If future occupants need to open windows for background ventilation, much of the façade sound insulation benefit is lost.

Scope of Assessment

Environmental Noise Survey

Polaris Acoustics carried out an unattended environmental noise survey using Class 1 precision sound-monitoring equipment.

The monitoring position was selected to capture the dominant road traffic noise affecting the most exposed façade. The survey measured daytime, night-time and maximum noise levels, allowing the assessment to consider LAeq,T and LAFmax values relevant to residential design.

BS 8233 Residential Assessment

The measured noise levels were assessed against the internal ambient noise guidance in BS 8233:2014.

Detailed façade calculations were undertaken to determine the acoustic performance required from the glazing and building envelope. This allowed different recommendations to be made for the more exposed road-facing rooms and the less exposed rooms away from the main road.

ProPG Acoustic Design Review

The site was reviewed using the ProPG: Planning & Noise approach for new residential development.

The measured noise climate placed the site within a medium to high noise risk category, meaning that a more detailed acoustic design response was required. The assessment therefore considered not only measured noise levels, but how the building design, façade specification and ventilation strategy would work in practice.

Ventilation and Overheating

The assessment considered Approved Document F, Approved Document O and the AVO Guide.

For the most exposed rooms, open windows were not considered suitable as the primary means of background ventilation. A mechanical ventilation strategy was therefore recommended so that suitable internal noise levels could be achieved with windows closed.

Residents would still retain the ability to open windows for purge ventilation, but the acoustic design would not rely on open windows being used for everyday background ventilation.

Commercial Noise and Plant

The existing kitchen extract plant was reviewed as part of the commercial noise context. Measurements confirmed that the fan was a relevant local noise source. Its removal as part of the redevelopment was therefore identified as an acoustic improvement compared with the existing arrangement.

Future M&E plant details were not finalised at planning stage, which is common for schemes of this type. To control this risk, plant noise limits were recommended in accordance with BS 4142:2014+A1:2019.

Key Findings

Issue	Finding	Design Response
Road traffic noise	The road-facing façade was the most noise-exposed elevation	Enhanced acoustic glazing recommended to exposed rooms
Night-time events	Individual vehicle pass-bys were relevant to bedroom design	LAFmax considered alongside average LAeq,T levels
Ventilation	Open windows were not suitable as the main background ventilation route for exposed rooms	Mechanical ventilation recommended
Overheating	Acoustic design needed to be coordinated with overheating strategy	Approved Document O and AVO Guide considerations included
Kitchen extract plant	Existing extract fan was identified as a local noise source	Removal of the existing plant represented an acoustic improvement
Rear service area	Occasional parking and servicing activity reviewed	No significant adverse impact identified
Future plant	Final plant selections were not confirmed at planning stage	BS 4142 plant noise limits recommended

Acoustic Design Response

The acoustic solution combined façade sound insulation, ventilation advice and plant noise control.

For the most exposed rooms facing the road, enhanced acoustic glazing was recommended to achieve suitable internal noise levels. For rooms without a direct view of the main road, a lower glazing specification was considered suitable, subject to final product selection and detailed design.

The ventilation strategy was a key part of the assessment. For road-facing rooms, the report recommended that background ventilation should not rely on open windows. This helped ensure that the specified glazing would remain effective during normal occupation.

The existing kitchen extract fan associated with the previous commercial use was also addressed. Its removal as part of the redevelopment reduced the potential for commercial plant noise affecting nearby residential receptors and future occupants.

For any future fixed plant, BS 4142 noise limits were set to provide a clear design target and avoid unacceptable impact on both existing and proposed residential uses.

Planning Outcome

Following submission of the Polaris Acoustics noise assessment, the scheme received consent from the local planning authority.

No further noise comments were raised and no noise-related planning conditions were attached.

For a residential conversion within a mixed-use town centre setting, this was a strong outcome. The assessment addressed the key acoustic risks at planning stage, including road traffic noise, commercial noise, kitchen extract plant, rear service activity, glazing, ventilation, overheating and future plant noise.

Relevant Experience

Residential conversion projects often require more than a simple noise survey. A robust assessment needs to explain how the proposed homes will function in practice, particularly where new dwellings are introduced above or near commercial premises.

For similar schemes in Totton, Southampton and wider Hampshire, the main acoustic risks often relate to road traffic noise, commercial plant, extract systems, servicing areas, ventilation and overheating. These issues should be considered together so that planning officers and Environmental Health consultees can understand the full design response.

This project demonstrates how a clear residential conversion noise assessment can help reduce planning uncertainty and provide a practical route to consent.

Prepared by Polaris Acoustics

This assessment was prepared by Mathew Vaughan BA (Hons) MSc MIOA, Founder of Polaris Acoustics.

Polaris Acoustics provides planning noise assessments for residential, commercial, industrial and mixed-use developments across the UK, including BS 8233 residential assessments, BS 4142 plant noise assessments, ProPG acoustic design statements and ventilation/overheating reviews.

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