The Growing Risk of Summertime Overheating.

Original Article
July 26th, 2023


Image shows air conditioning unit used to combat summertime overheating in homes

It is no secret that our climate is getting warmer. 2022 was one of the six warmest years on record globally, and the warmest year on record for the UK. With 2023 expected to be even warmer, hotter temperatures are becoming the norm.

As the changing climate causes summers to be longer and hotter, the risk of overheating in our homes increases. The Chartered Institution of Building Service Engineers (CIBSE) defines overheating as when an internal temperature of 28⁰C is surpassed for over 1% of the annual occupied time in living areas, and over 26⁰C in bedrooms. A more straightforward way of measuring overheating is simply when occupants feel uncomfortable due to high internal temperatures.

Leading drivers of summertime overheating

The impacts of overheating are varied, affecting health, wellbeing, and productivity. The Climate Change Committee (CCC) warned that the consequences of high summer temperatures are already being felt in the UK. They also noted that the problems will only be exacerbated as temperatures get hotter, predicting a potential trebling of health and productivity impacts without greater adaption.

The leading driver of overheating is warm outside air, but building design can also worsen matters, especially where overheating has not been considered from the outset. Properties with poor ventilation and large areas of glazing are more at risk of overheating. This is because insufficient ventilation prevents warm air from leaving properties and glazing increases internal heat gains from the sun.

Additionally, flats tend to be more likely to overheat, due to their typically low exterior wall to floor area ratio. Couple this with the urban heat island effect (higher temperatures experienced in cities due to heat generated from human activity and heat retained from the built environment) and it becomes apparent that high-rise urban flats are at high risk of overheating.

The introduction of Part O to reduce summertime overheating

To minimise the chances of building homes that are susceptible to overheating, in June 2022 Part O of the Building Regulations were amended to require new-builds to undergo an Overheating Risk Assessment. This helps to ensure that properties aren’t just designed for the requirements of today but are adaptive to the warmer future climate.

Outside of building design, the most obvious and effective way of cooling homes is air conditioning. The increased demand for air conditioning units has already been evidenced in the UK; in 2008 0.5% of homes had units, whereas in 2022 this had risen to 5%.

As temperatures continue to rise, air conditioning units will undoubtedly become more common. This creates another hurdle for net zero as air conditioning will lead to an increase in energy demand – so much so that in a recent report by the Department for Business, Energy & Industrial Strategy, they predicted that by the end of the century, the demand for cooling buildings could increase the UK’s power consumption by up to 15% during summer months.

With the risk of overheating becoming a greater concern as the climate gets hotter, we are forced into a catch 22 situation, where a leading solution in air conditioning will also compound the problem. This emphasises the importance of designing, building, and renovating homes with overheating in mind, ensuring properties are fit for the future and its warmer climate.

This article was written by Johnnie Leather, Public Policy Researcher at Sava.