The Problem
Until recently, the design of buildings considered the issues of acoustics, ventilation and overheating separately which directed to different considerations and/or recommendations from each specialist discipline.
In turn, this often led to building tenants being affected by poor ventilation and/or increased ambient noise levels, undoubtedly affecting their wellbeing.
The Guide
Section 2.4 of the Professional Practice Guidance on Planning & Noise (ProPG) refers to the importance of providing a thermal comfort/cooling strategy to reduce potential impacts of noise on future occupants of a new residential development.
The Acoustics Ventilation and Overheating (AVO) guide is intended to demonstrate good acoustics design as described in the ProPG, when considering internal ambient noise levels guidelines. It is intended for the consideration of new residential development that will be exposed predominantly to airborne sound from transport sources, and to sound from mechanical services that are serving the dwelling in question.
The document suggests that the desirable internal ambient noise levels should be achieved,
when providing adequate ventilation as defined by Building Regulations Approved Document F - Whole dwelling ventilation.
However, it considers reasonable to allow higher levels of internal ambient noise levels from transport sources when higher rates of ventilation are required in relation to the overheating condition.
A two-level noise assessment procedure is proposed to determine the significance of impacts. Qualitative guidance on the combined effect of internal ambient noise levels and duration for the overheating situation is provided in the document.
The limits for internal ambient noise levels during the overheating condition, as shown in the Figures below, may be considered (example).
It can be seen that the Significant Observed Adverse Effect Level (SOAEL) varies depending on the duration for which the overheating condition occurs.
Possible Outcomes
The determination of the duration for which the overheating condition occurs can be carried out by means of a dynamic modelling in line with CIBSE TM59. This will enable the design team to determine the required air changes per hour for each relevant space and specify the necessary dimensions and capacity for each louver and comfort cooling system.
This information will enable the acoustic consultant to identify suitable products or solutions to achieve appropriate internal ambient noise levels both for ADF ventilation and overheating situations.
Some of the design solutions are shown below, for reference.
Final Considerations
The AVO guide is an important and revolutionary document that allows for the provision of thermal comfort/cooling strategy whilst reducing potential impacts of noise for future residents.
It should be considered for the design of all residential developments, in line with the recommendations of the NPPF and NPSE.
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