Acoustic ambitions for a better built environment – part 5.


Systems thinking.

In this series, we have covered several of the case-by-case conundrums facing the acoustics community.

The question the acoustics community is presently asking itself is whether the design of the high-performance building of the future could benefit from acoustic designers taking a step back to look at the issues from a systems perspective, and not just in isolation but in tandem with engineers and designers from other technical disciplines.

When we talk about adopting a systems thinking approach to the issue at hand, we need to consider the window as an integral part of a system which includes not just the whole of the building’s façade, but also the building’s ventilation and thermal management systems and strategies.

A modern approach
Recent advances in modern methods of construction (MMC), including the multiple benefits to be gained from off-site factory production environments, opens the possibility of better integrating multiple outcomes within the design and construction of the fundamental building structure itself. Focusing on acoustics here, complete façade elements (including any windows) could be delivered to site with a guaranteed composite sound insulation performance. These façade elements could include integral features such as controllable ventilation paths with built-in acoustic attenuation to control the ingress of external noise and the egress of internal noise.

Current developments in acoustic metamaterial technology could revolutionise the form such acoustic attenuation would take, as could future developments in active noise control.

The integral ventilation paths would no longer have to rely on the windows and could therefore also include integral air movement devices, possibly powered by built-in energy harvesting elements also integrated into the façade itself. These façade-integrated ventilation paths could equally host thermal transfer and air filtration components. All of this could be made possible by the façade being manufactured under closely controlled factory conditions, as opposed to being constructed under variable on-site conditions. The associated environmental benefits of reductions in energy, embodied carbon and waste in both manufacture and construction, plus greater material traceability and circularity, could be significant. Equally significant would be the guarantee of such precision manufactured units delivering better installed performance in all regards, including human-centric outcomes.

Intelligence is everything
Also worthy of consideration as part of any new approach to the design, delivery and operation of high-performing buildings is the impact that advances in building intelligence, often referred to as smart building technologies, may have. The prudent and targeted deployment of these technologies could simultaneously yield both better human-centric and planet-conscious outcomes.

The windows we’ve been discussing need to provide adequate ventilation and cooling to internal spaces (often via opening windows) while, at the same time, protecting against the ingress of external noise. Under many practically encountered situations, external noise levels are not constant but instead exhibit significant diurnal variations. This is particularly the case with road traffic noise, which is the predominant source affecting buildings. Likewise, acceptable levels of noise in internal spaces may also vary depending on the time of day or night. However, as previously mentioned, the common ‘solution’ to protecting building occupants against external noise is to include non-openable windows in noise-exposed façades.

The problem with this solution is that it removes the option for building occupants to choose natural ventilation via open windows even at those times when the external noise levels are acceptably low.

It also removes the option to cool an internal space via fresh air circulation even when that space is unoccupied, in which case the ingress of external noise cannot possibly be an issue as there is no one there to experience it.

A more targeted approach to maintaining the appropriate balance between human-centric and planet-conscious outcomes could be based around evidence provided by sensed data. The real-time monitoring of internal versus external environmental conditions could provide essential information to building users, allowing them to regain control in weighing up the benefits/disbenefits of taking certain actions. For example, the simultaneous monitoring of external and internal noise levels, temperature and air quality could all provide information on which building occupants could take the appropriate action of opening or closing the windows. The same information could equally be employed to drive automated control processes for implementing any ventilation versus noise control strategies.

To better engage building users, evidence could simultaneously be provided as to the anticipated benefits resulting from any such automated control, both from an indoor environmental quality and an energy-saving perspective.

There also exists the possible sensing of occupancy patterns simultaneous with the monitoring of internal environmental quality, including the acoustic environment, to gather real-world evidence on the degree to which sound contributes to occupants’ preferred choice of locations. Such information could usefully inform future acoustic design criteria on the basis of behavioural as opposed to questionnaire-based evidence.

In the final part of this series, we look beyond the building to the wider ecosystem…

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