Planning Consultation Guidance Notes

5.1. Introduction to the section

This chapter reviews a number of elements relating to how noise impacts for residential development can be mitigated. The principles for mitigation of noise impacts are outlined below and follow the hierarchy pyramid principles set out in Figure 1. Hierarchy levels must be considered starting with level 1. The assessor should only move on to the next level when they have fully considered and implemented all reasonable measures that may be applied and where necessary justified why a measure is not practical for the application. The principles of good acoustic design must be followed. Noise should be a consideration at the earliest stages of planning a new development. We expect that ProPG: Planning & Noise, New Residential Development: Supplementary Document 2 Good Acoustic Design will be followed.

Hierarchy Level 1
Control of noise at source to enable noise sensitive development

Where there is an existing noise source such as from a separate industrial, commercial or entertainment premises, the first option for consideration is reducing the noise from that source. The noise assessment should detail the options that have been considered, which may include operational controls to minimise the source noise (such as hours of use), insulation or attenuation at source, enclosure of outdoor sources or provision of a noise barrier. The applicant will need to agree an approach with the responsible party. ECP will in turn evaluate the technical merits of the proposed solution. In these circumstances these source-control measures must be in place prior to the occupation or operation of the new development. Where such options exist, there may be an economic benefit to the applicant to assist in reducing noise at source rather than to meet increased insulation requirements and this will also provide for greater protection for external amenity areas or minimise the impacts on the new receptors.

The NPPF has introduced the 'agent of change' principle which requires an applicant introducing a new land use to manage the impact of that change.

In the case of a residential development, this requires the 'agent of change' i.e. the applicant/developer to identify the noise from existing businesses that have an adverse effect on new residents or users. The agent of change will need to consider not only the current activities, but also those activities that businesses or other facilities are permitted to carry out, even if they are not occurring at the time of the application being made. The applicant will need to explore mitigation options and if possible, agree a detailed mitigation scheme with the responsible third party to control the noise at source. ECP will in turn evaluate the technical merits of the proposed solution. In these circumstances these source-control measures between the agent of change and any third party must be clearly set out in an agreed via a unilateral legal agreement which clearly details the following:

•  the scope of mitigation works
• who is responsible for carrying out the work and by when
• confirmation that the mitigation will be in place prior to the occupation or operation of the new development

There may be other elements that will need to be included in the agreement in addition to those stated above. Any legal agreement must be approved by ECP and the council's planning department prior to planning permission being approved.

It can also be helpful for developers to provide information to prospective purchasers or occupants about mitigation measures that have been put in place, to raise awareness and reduce the risk of post-purchase/occupancy complaints.

Hierarchy Level 2
Site layout and design

Many potential noise problems can be resolved through the careful design and layout of a site.
The checklist below should be considered as early as possible in the design of a residential scheme.

Hierarchy Level 3
Dwelling layout and orientation

Many potential noise problems can be resolved through the careful design of noise-sensitive premises. The following checklist should be considered as early as possible in the design of a scheme.

Hierarchy Level 4
Planning restrictions

Planning conditions may be used to control the source of the noise if it is part of the planning application. This may include restrictions on hours of use (e.g. to avoid noise sensitive times such as late evening, night-time and early mornings), restrictions on power levels of equipment, restrictions on music or equipment, sound levels or a requirement for a noise management plan or quiet delivery plan implementation. If noise levels are dependent on restrictions of this nature, the application must suggest appropriate restrictions that may be included in conditions. These conditions must meet the planning 6 tests as set out in the NPPF.

Hierarchy Level 5
Building envelope

Reliance on the building envelope must be the last consideration once all other reasonable measures have been utilised. The noise exposure hierarchy table in the PPG Noise identifies having to close windows, where there is no alternative ventilation, to reduce noise levels as an adverse impact. The severity of the impact depends upon how often it is necessary to close the windows. An option that is sometimes considered to achieve a satisfactory internal noise environment, is sealing of the building envelope (i.e. through the provision of non-open able windows). However, this is considered a poor acoustic solution and as such should only be considered where this is necessary for air quality reasons. Where reliance on closed windows for part of a dwelling is deemed appropriate it will be necessary to avoid overheating and to provide sufficient ventilation to provide comfort cooling. In such circumstances, trickle vents are not considered appropriate. The provision of an alternative form of natural ventilation will be required to aid thermal comfort. If this is impracticable then a Mechanical Ventilation Heat Recovery (MVHR) system with fully automated summer bypass may be acceptable. A separate overheating assessment for the development may also be necessary in such circumstances.

For noise from transportation sources, the ProPG(8) (which provides guidance on new residential development) concurs with the PPG(Noise) when it comes to the need to close windows in order to achieve a satisfactory noise climate within habitable rooms. The ProPG includes the following statements with regard to opening windows and indoor noise levels:

Using fixed unopenable glazing for sound insulation purposes is generally unsatisfactory and should be avoided; occupants generally prefer the ability to have control over the internal environment using openable windows, even if the acoustic conditions would be considered unsatisfactory when open. Solely relying on sound insulation of the building envelope to achieve acceptable acoustic conditions in new residential development, when other methods could reduce the need for this approach, is not regarded as good acoustic design. Any reliance upon building envelope insulation with closed windows should be justified in supporting documents. (Paragraph 2.22).

and

It should be noted that the acoustic performance of the building envelope will be reduced in the event windows are opened for ventilation or cooling purposes, typically reducing the insulation to no more than 10 to 15 dB(A). Most residents value the ability to open windows at will, for a variety of reasons, and LPAs should therefore normally request that designers principally aim, through the use of good acoustic design, to achieve the internal noise level guidelines in noise-sensitive rooms with windows open. Where internal noise levels are assessed with windows closed the justification for this should be included in the Acoustic Design Statement. (Paragraph 2.33)

The ProPGonly considers noise from transportation sources. Occupants are usually more tolerant of a noise without a specific character than, for example, that from neighbours which can trigger complex emotional reactions. (BS 8233:2014 (Para 7.7.1)). Therefore, this department will not normally accept closed windows and alternative ventilation to mitigate noise from entertainment, industrial and commercial uses.

(8. Planning and Noise. Professional Practice Guidance on Planning and Noise, New residential development. IoA, ANC and CIEH May 2017.)

Summary

1. ECP will not accept any strategy that recommends the use of non-openable windows for residential properties as a means of securing the internal acoustic environment.
2. Where openable windows are provided, ECP will not accept a strategy that relies on the occupier of the noise sensitive premises having to close the window during noisy activities.
3. A mitigation strategy that includes closed windows for noise without character will only be considered by ECP once all other acoustic mitigation measures have been considered and implemented where possible. In these circumstances, the number of closed windows must be restricted to a minimum of habitable rooms and never for a whole dwelling.

5.2 Ventilation

The primary document for determining any standard of ventilation is Approved Document F, Ventilation, issued under the Building Regulations 2000. Ventilation within any residential or hotel premises must comply with the provisions of this document.

Where enhanced glazing or other mitigation to the building envelope is necessary to ensure the indoor noise climate is acceptable, it will be necessary to provide a scheme of ventilation to remove the need to open windows other than for purge ventilation. The ventilation scheme will be expected to provide thermal comfort during summer months; acoustic trickle vents will not be sufficient in such circumstances.

Overheating is regulated through Building Regulations Approved Document O. The Association of Noise Consultants(9) also provides guidance.

Any requirement for ventilation shall be met either via acoustic vents, a scheme of mechanical ventilation, or another method of ventilation which is comparable to the above.

In any case the ventilation proposed must not compromise the acoustic integrity of the building envelope. Trickle vents are only suitable where the overall noise mitigation of the building envelope meets acceptable internal criteria with windows open. Where overheating is a factor Approved Document O is relevant.

Where some form of mechanical ventilation is proposed, resultant noise levels due to the operation of the ventilation system at maximum rate should not exceed NR25 (However, the combined impact of noise break-through from the building envelope and noise generated by any mechanical ventilation at maximum rate shall at all times meet the requirements of this section and the internal noise criteria provided in Section 7.7 of BS 8233.

In all instances where mechanical ventilation is proposed, the design statement should consider the air quality around the development to ensure the highest quality of intake air.

(9. Association of Noise Consultants-Acoustics Ventilation and Overheating-Residential Design Guide; January 2020)