Demonstrating compliance with the new Part O building regulation should be a priority now for housebuilders

The Egyptians and Romans knew exactly how to do it. Even the Victorians got it. But now the government has stepped in with new building regulations – Part O in England – to address the fact that we seem to have lost the art of correctly orientating, designing and constructing homes that don’t overheat for days on end in hot weather.

Stuart Fairlie

Over the last 20 years, building regulations have evolved to encourage higher levels of insulation, more airtight buildings and increased solar gains. While this is great for energy efficiency, one of the unintended consequences of this is that buildings are more likely to overheat. As the climate warms, overheating in buildings is becoming an increasingly widespread issue.

Therefore Part O is concerned with two issues mostly: how to limit unwanted solar gains in summer and how to remove excess heat from the indoor environment, ideally avoiding the use of carbon-intensive air conditioning which, of course, just compounds the problems of climate change and exacerbates deadly heatwaves in the first place.

> Also read: Revised building regs mandate 30% cut in carbon for all new buildings

One myth needs busting: this isn’t just about London flats. The problems of unbearable overheating over extended periods of time can be much worse in urban areas, and in apartments, it’s true, especially where hot water pipes and other services with radiant heat run in voids above corridor ceilings and other common parts, for example. But it can also be a lethal problem in a wide range of new homes, residential institutions, halls of residence and student accommodation.

There are about 2,000 heat-related deaths in the UK every year, which is anticipated to triple by 2050 due to climate change

And it’s not just about us becoming tired and grumpy after periods of no sleep. According to the Department for Levelling Up, Housing and Communities, there are about 2,000 heat-related deaths in the UK every year, which is anticipated to triple by 2050 due to climate change.

However, technical experts agree that tackling overheating is actually fiendishly complicated, so the new regulations are taking a relatively light-touch approach for starters.

Overheating has been removed from Part L and SAP assessments. Instead, in Part O, there’s a “simplified method” for demonstrating compliance which is very prescriptive but should be relatively easy for housebuilders to follow. Or there’s a dynamic thermal modelling method which uses the expertise of CIBSE TM59 calculations and gives designers and housebuilders much more flexibility in how they approach the overheating issues.

It’s a very welcome start. What’s also very good news for those who care about the quality of new homes is the transitional arrangements which are attached to these regulations. They take effect from 15 Junethis year and any plot started after then must be up to the new standard within a year.

I think it’s likely we can expect more complex versions of these regulations and tougher requirements coming in over time, as part of the journey towards the Future Homes Standard.

But even now, we can see that housebuilders will need real technical expertise at hand to help them demonstrate compliance, to navigate the complex ways in which Part O interacts with multiple other parts of the building regulations, and to achieve more intelligent and cost-effective ways to reduce high indoor temperatures in their homes, particularly apartments.

We’re getting a very positive response already to our new Overheating Competency Scheme which aims to give housebuilders and social housing developers access to a bank of fully qualified overheating assessors by June. Training of these assessors has already begun.

Will these assessors be much in demand? We think so. It’s noticeable that the new regulations go beyond the traditional focus on health and safety – Part O specifically talks about the need to ensure occupants’ “reasonable enjoyment of the residence”. In the face of stricter building control checks and a new regulatory regime for housebuilders, including the New Homes Ombudsman, many builders will be looking carefully at the best way to achieve compliance that doesn’t get them hot and bothered.

Stuart Fairlie is managing director of Elmhurst Energy.