The current situation
The general comfort of a building’s occupants is dependent on factors such as indoor air quality (i.e. ventilation), thermal comfort and acoustic comfort. These factors are interdependent but are typically assessed independently by different designers and based on different assumptions regarding use of the building. For example, it is not unusual to find that a noise assessment concludes that windows need to be closed to achieve reasonable internal noise conditions, whilst the overheating assessment calls for open windows for reasonable thermal conditions.
Excessive internal temperatures are partly explained by the increased airtightness and enhanced thermal insulation of modern homes. An unintended consequence of this is that the dissipation of excessive heat can be difficult. Other contributing factors include global heating (i.e. climate change) and the urban heat island effect.
It has become more and more common to encounter buildings in which occupants feel the need to open windows to regulate internal temperatures to a comfortable level. By doing so, however, those occupants may be exposed to levels of noise which the acoustic design of the building intended to avoid. This results in dwellings in which occupants may choose between having acoustic comfort or thermal comfort but cannot have both simultaneously.
This situation is at odds with the concept of placing the occupants’ health and wellbeing at the centre of housing design. Therefore, an integrated approach to residential building design is needed.
The new approach
The Association of Noise Consultants and the Institute of Acoustics jointly published the Acoustics, Ventilation and Overheating Residential Design Guide (‘AVO Guide’) in January 2020 to help acousticians conduct noise assessments with due regard for ventilation and mitigation of overheating.
The AVO guide recognises that the acoustic requirements of building designs should be integrated with the ventilation requirements to provide homes that are sustainable and achieve good indoor air quality, thermal comfort and acoustic comfort. This is especially important where the increased demand for new housing results in building closer to highways, railways and flight paths than would otherwise be desirable.
In pursuit of this objective, the AVO Guide helps acousticians to:
- Determine the appropriate internal noise levels, due to transport noise sources, under different ventilation conditions;
- Determine the appropriate internal noise levels, due to mechanical ventilation systems serving the dwellings, under different ventilation conditions;
- Assess how the ventilation strategy impacts on the acoustic conditions;
- Assess how the strategy for mitigating overheating impacts on the acoustic conditions;
- Develop options to suitably control external noise ingress in conjunction with adequate ventilation and mitigation of overheating;
- Develop options to suitably control noise from mechanical services in conjunction with adequate ventilation and mitigation of overheating; and
- Apply a consistent and practical approach to assessing noise impacts under different ventilation and overheating conditions.
This new approach requires closer collaboration between acousticians, overheating risk analysists, MEP engineers, building physicists and the wider design team.
The next steps
In time, local planning authorities may demand a holistic approach to residential design (such as that encouraged by the AVO Guide) for all new developments, but perhaps building designers should not wait for this to become mandatory. Better quality housing, for the benefit of the occupants, may be incentive enough.
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