Sound Advice: How Acoustics Impacts Overheating in Buildings

Christina Higgins is Acoustics and Building Physics Lead at Rimkus. She has an MSc in acoustic engineering, a PhD in civil and environmental engineering, and spent over a decade as an acoustic consultant in the construction industry. She takes a holistic, systems-thinking approach to building performance and occupant comfort. In this series, Christina will walk through examples of the interfaces between different building physics issues that lie at the root of construction claims and disputes.

Acoustics and overheating

At first glance, acoustics and overheating in buildings don’t appear to be linked. Acoustics is concerned with noise in and around buildings, and overheating describes the case in which the temperature inside a building exceeds a level which is comfortable.

Factors which influence overheating in buildings

Overheating is a complex issue that usually stems from the interaction of several different factors, including:

• External climatic conditions, including the urban heat island effect;
• Building location, orientation, solar exposure, and shading by surrounding buildings;
• Building envelope design (thermal properties of the building elements, size and location of windows);
• The heating and cooling systems supplying the building; and
• The ventilation provision (whether hot air can be adequately “purged” from the space).

This last one is where the acoustic design becomes a contributing factor.

Noise levels and building design

New developments requiring planning permission will typically have a noise impact assessment conducted, which involves measuring the existing noise levels around the site. The noise levels are assessed to determine whether they require attenuation to be quiet enough inside the building (spoiler alert – in cities, they almost always are). The attenuation/reduction of the noise levels is achieved by the structure of the building façades, including the windows. If it’s noisy enough outside, then with open windows, it will be noisy inside too. This can cause disturbance to occupants, affect sleep, and lead to adverse health effects.

It has been common for the acoustic consultant, who undertakes the noise impact assessment, to recommend that a building with high external noise levels have a sealed façade (no openable windows), and that the ventilation be provided mechanically. Since the UK is a temperate climate which, until recently, rarely experienced excessively hot days, comfort cooling (air conditioning) was rarely included with this mechanical ventilation. Couple this with the architectural trends for large glazing (sometimes floor to ceiling), single aspect layouts, and the other factors detailed above, and we now have a perfect storm of overheating cases in the UK.

How do we assess overheating?

Overheating is assessed against different criteria depending on the building use (e.g., residential or office). Since 2022 the Building Regulations Part O has required that reasonable provision be made to limit solar gains and provide an adequate means to remove heat. For buildings designed prior to this, there was applicable industry guidance such as CIBSE Guide A, TM52 and TM59, and, for dwellings, a requirement in Building Regulations Part L to limit solar gains. So as with any other building claim or dispute, it’s important to situate an overheating issue within the guidance and regulation applicable at the time of design is to get to the root of liability.

At Rimkus, our Building Physics and Acoustics team at Rimkus are well-placed to investigate any overheating issue.

Frequently Asked Questions

What is overheating?

Overheating in buildings refers to the case in which temperatures exceed a level that is comfortable to occupants. A building is usually considered to be overheating if the internal temperatures exceed a certain level for a percentage of time during a calendar year, with the specific criteria dependent on the building use (e.g., residential or commercial).

What is acoustics?

Acoustics is the study of how sound waves propagate. In building design, acoustics is concerned with noise transfer in and around buildings.

How is acoustics linked to overheating?

If the noise levels at a site are high, an acoustic consultant might recommend, during the planning application stage, that the building have a sealed façade and no openable windows, with ventilation supplied mechanically. Without the ability to open windows for “purge” ventilation, and without adequate “boost” provision or cooling from the mechanical systems, excess heat can become trapped inside the building.