Thermal Mass Can Address Offsite Overheating Concerns

12 Oct 2018

A report by the Commons’ Environment Audit Committee earlier this month, which claimed that “modular homes are not resilient to heatwaves”, has stirred up considerable debate during one of the hottest summers that Europe has experienced for decades.

Trade body Buildoffsite hit back at challenges to the performance of lightweight modular homes, saying “good offsite design gives excellent mitigation of overheating”.

Then Bob Ward, policy and communications director at the LSE's Centre for Climate Change Economics and Policy expressed his serious concerns about overheating in new-build housing, in an article for The Guardian. Ward is also deputy chair of London Climate Change Partnership (LCCP),
The Concrete Centre understands the unease of Ward, who wrote, “as ever, those who are least able to deal with the problems are quite often the ones most deeply affected by them, and when developers cut corners on design, occupants usually pay the price”.

We also believe the Environmental Audit Committee report, ‘Heatwaves: adapting to climate change’, makes a valid point about overheating in modular homes – as this is most likely to be more of an issue in lightweight homes that have little inherent thermal mass.
The technical guidance that The Concrete Centre provides for designers includes how to use thermal mass, in combination with shading and ventilation for cooling in summer, as essential in managing the risks of overheating. On occasions, these passive measures may need to be supplemented with active cooling in some climate change models and in some building types, such as high-rise apartments.

In the past, The Concrete Centre has worked with the Zero Carbon Hub and is now working with the Good Homes Alliance to provide evidence-based best practice to planning departments on the risks of overheating.

It is important that proven performance and evidence shapes this debate, to provide housing that is resilient to climate change that will perform both now and in the future.

Those in the offsite sector who produce lightweight systems are not happy about the Environmental Audit Committee report recognising that many factory-produced homes which are of lightweight construction lack thermal mass. But the fact remains that thermal mass offers an effective means of helping to reduce overheating when used in conjunction with good ventilation and solar shading.

If we are going to tackle the problem of heatwaves without resorting to energy intensive air conditioning (as per the USA), then we need to employ all the passive measures available to us, of which thermal mass, inherent in masonry and concrete, has an important role to play.

Tony Jones is principal structural engineer at The Concrete Centre