Following two years work and more than a handful of meetings, the Association of Noise Consultants (ANC) published the draft version of the “AVO Guide” in February 2018. This Guide marks a significant step forwards in the assessment of internal environmental conditions in residential developments, and hence invites the industry to step up to the design challenge. TEK, with their new range of products to enable natural ventilation in noisier environments, are demonstrating their position at the forefront of meeting this new design challenge.
The AVO Guide enables and encourages developers to design new dwellings in a way that considers the effects of both thermal comfort and acoustic comfort at the same time. Traditionally, these issues have been considered separately, so that occupants of new dwellings that are exposed to high levels of environmental noise are forced to choose between comfortable temperatures with the windows open, or comfortable and safe noise levels with the windows closed. Jack Harvie-Clark and Anthony Chilton presented the draft in a CIBSE webinar that you can watch. Jack presented the draft Guide at the CIBSE Symposium in April 2018 – you can download the supporting paper on the CIBSE website here.
We have known for some time that we need sustainable, resilient dwellings that are comfortable for the occupants. We know that people like simple controls over their environment; the act of opening a window or vent is intuitive to meet a need for ventilative cooling and for air movement to increase the cooling effect. There is a clear conflict between the benefits of opening windows, and the risks associated with excessive noise. A fragmented design approach results in residential accommodation that may be uncomfortable to occupants, and hence may be considered unsustainable. Residual risks for stakeholders include:
- Health & wellbeing risks for occupants
- Design risks for consultants; and
- Legal risks for developers
Designing for internal environmental quality
Historically, external noise considerations and facade sound insulation have been deliberately excluded from Building Regulations, as they are site-specific issues. The Planning system is therefore currently seen as the regulatory regime with the best opportunity to require concurrent consideration of noise and thermal comfort, even though these issues would seem to sit within the remit of Building Regulations. In the past there have only been occasional Planning requirements to consider the indoor noise and mitigation of overheating in an integrated, holistic manner. With the previous lack of appropriate design criteria and little explanation of the issues in the complex and inter-related fields, it has been difficult for Planners and Environmental Health practitioners to specify suitable requirements. Apex Acoustics has demonstrated that in 85% of planning applications, the acoustic designers assumed that windows were closed to provide acceptable acoustic conditions, while the mechanical designers assumed windows were open to provide acceptable thermal conditions.
The Association of Noise Consultants’ draft Acoustics, Ventilation & Overheating: Residential Design Guide, addresses these issues. This ground-breaking guide proposes allowing tolerances over the annual average internal noise level limits that are normally applied to new dwellings, for the reduced portion of the year when opening windows may be required to mitigate overheating. It suggests a balanced approach, such that if the overheating risk is lower – with less reliance on opening windows, for less frequent periods – then it is suggested that occupants may accept slightly higher noise levels. If there is a high reliance on opening windows, such that they are required for a greater proportion of the year, then a lower noise level limit would be more appropriate. The identification of design criteria enables the industry to respond by developing the most advantageous solutions – such as those by TEK Ltd. In many locations where new residential development is desirable opening windows permit excessive external noise ingress, and attenuated vents may be a more appropriate solution. The draft Acoustics, Ventilation & Overheating: Residential Design Guide provides a framework for assessment and separate criteria to associate with both ventilation and provision of thermal comfort. External noise is treated separately from internal (building services) sources of noise, because people respond to these different noise sources in different ways.
Contents of the AVO Guide
The AVO Guide includes:
- an explanation of ventilation requirements under the building regulations as described in ‘Approved Document F – Means of Ventilation, 2010 Edition’ (‘ADF’) along with typical ventilation strategies and associated noise considerations;
- an explanation of the overheating assessment methodology described in CIBSE ‘Design methodology for the assessment of overheating risk in homes’ (TM59);
- acoustic criteria and guidance relating to different ventilation and overheating conditions, for both environmental noise ingress and building services noise; and
- a worked example of the application of the AVO Guide including indicative design solutions.
We look forward to developing the most advantageous solutions for future residents, so that people can enjoy thermal comfort within their homes without being subject to harmful and annoying levels of noise. TEK’s new range of products offers a designers a real opportunity to achieve comfortable conditions for residents within sustainable, resilient buildings.
Jack Harvie-Clark, Apex Acoustics Ltd.