The risks of overheating are real – and we must take them very seriously

The government’s heatwave mortality statistics for 2020 show that there were 2,556 excessive deaths attributed to heatwaves that year. There were a significant number of excessive deaths in all regions of England except two in the North-east. We should therefore not think that summertime overheating in buildings – or its impacts – occurs only in London and the South-east of England.

The government predicts that the number of annual deaths associated with overheating will triple by the 2050s. The majority of these deaths are in the over-65 age group, with a higher proportion than average among the over-85s, but the data shows that excessive deaths occur in every age group, although the problem becomes greater from the over-45 age group upwards.

Overheating in residential buildings of all types is attributable to a whole host of factors. These include rising summer temperatures, dense urban developments, the urban heat island effect, single aspect apartments, enhanced insulation levels and lower air permeability rates, lower ceiling heights, lightweight construction systems, large glazed areas, external noise preventing windows being opened, communal heating systems (including distribution pipework), mechanical ventilation systems which are poorly installed or do not operate correctly as well as occupant behaviour.

Little attention has been paid by some developers and designers to overheating in recent years

A combination of some or all of these factors can lead to excessive heat gain in dwellings, especially contemporary flats, student housing and later living accommodation.

It seems that little attention has been paid by some developers and designers to overheating in recent years. There is a requirement in the London Plan for overheating analysis against the policy requirements at planning stage, but this is not regulated at later stages of the development process.

There has been no requirement to consider overheating within building regulations other than the very basic analysis in the building regulations regulated energy software (SAP),  which was easy to pass by entering unrealistic yet allowable window opening behaviour. There has been no incentive to consider mitigation of solar gain when buyers are typically unlikely to want external shading devices and they add costs to an already financially competitive development.

However, the incentive to seriously consider overheating has to be risk. I have foreseen for a number of years that overheating presents health risk to individuals and commercial risk in the form of excessive deaths happening in the residential buildings that the industry designs, develops, constructs and manages.

We could see dwellings deemed unfit for habitation on the basis that they get too hot in summer

In the future, a death or deaths in a building which are attributable to overheating could mean legal action against the parties involved in the design, development and ownership of the building. Claiming that there was no statutory requirement to consider overheating mitigation may not be an adequate defence, given that the evidence data and impact predictions have been available for 20 years.

With the proposed 30-year retrospective Defective Premises Act changes, we could see dwellings deemed unfit for habitation on the basis that they get too hot in summer.

There is of course going to be a statutory requirement to consider overheating in residential buildings from mid-June this year when part O of the building regulations is introduced. The new regulations apply to residential dwellings, later living developments and student accommodation.

The goal of the regulations is to ensure that the design and construction of buildings limits solar gain during the summer months and provides occupants with adequate means of removing excess heat from indoor environments.

This new requirement has seemingly crept up on the industry, with many organisations not being aware it was coming

This new requirement has seemingly crept up on the industry, with many organisations not being aware it was coming. Perhaps they were otherwise focused on managing the impacts of covid and emerging building safety legislation, but there is not much time to react and some designers and developers are quickly trying to assess the impact on projects which will not be able to be submitted as a building regulations application before mid-June this year.

Of course, for those who beat the deadline, there should be a consideration as to whether not demonstrating compliance with part O – when you knew it was coming – would be adequate defence in a future claim situation.

We should all be very wary of the impacts of overheating and the need to carefully consider how the buildings we design and develop respond to the risks that it presents.