Overheating is costing lives and Specialist Building Service Engineers, Milieu, have decided to share their expert knowledge of competing demands of design, to help prevent overheating in residential builds.

The government may encourage people to open their windows to mitigate the risk of Covid-19 transmission this winter. Yet, there will be some individuals who may not have the physical or mental capacity to open windows at all, or they may live in homes where windows cannot be opened due to security issues and/or noise pollution. It is these people who are also at higher risk from overheating in the summer months when they are unable to open windows to cool down.

Often overlooked, there is a very real risk of death in the UK due to overheating – almost 900 pensioners died last year during Britain’s summer heat waves, and the Committee on Climate Change has estimated that mortality rates arising from overheating could, without any adaption from the population, rise from a current average of 2000 per year to 7000 per year by the 2050s.

To reduce the risk of overheating in a residential build, there are a number of competing demands to consider: all of which need to be balanced by careful planning and design.

• Acoustics – internal noise levels have to fall within acoustic requirements for residential buildings: this can mean windows may not be openable as would allow too much noise, so cooling via windows is impossible.
• Daylighting – glazing installed to allow sufficient daylight to penetrate into rooms: but, too much glazing, especially on south and west facing buildings can lead to high levels of solar gain and increase risk of overheating.
• Energy – buildings need to be well-insulated to prevent heat-loss and reduce the use of heating systems thus reducing carbon emissions: however, well-insulated buildings trap heat and increase risk of overheating.
• Overheating – buildings need a way of letting excess heat escape to prevent occupant discomfort. If a building is very well-insulated, has windows that can’t open due to acoustic requirements and has high levels of glazing to satisfy demands for daylight, occupants are at increased risk of overheating.

Passive methods of cooling, such as opening windows and doors and closing shutters and blinds, are the most desirable to reduce risk of overheating, but these cannot always be achieved. Overheating needs to be taken into account at the design stage of a building. Retrospective cooling is a lot more costly and less energy efficient.

“Every development is unique and requires individual consideration. We find that the most efficient and cost-effective way to address the competing demands of design is for building service engineers to be involved from the initial stages: early engagement with architects and developers to understand the challenges of a development and to assess risk of overheating, are essential to provide healthy living spaces, reduce risk of ill health due to overheating and reduce long term costs associated with retrofitting cooling solutions,” said Carl Carrington, CEO Milieu.

“An example of this in practice is our current work with Ayre Chamberlain Gaunt Architects on a new build development in the London Borough of Hackney. It’s impossible to use purely passive methods of cooling due to site-related constraints, so we’ve proposed to make use of underfloor cooling in order to avoid overheating within the apartments.”