UK cities have seen major growth in high-rise developments over the past five years.
While some of this has been from office developments, a large proportion is made up of apartment buildings.
Planners in Manchester, Birmingham and London have given the go-ahead for some of the tallest residential towers ever built in their areas.
Birmingham’s 45-storey Octagon topped out in September 2024 and is due for completion in 2025.
Manchester’s Deansgate Square South Tower is 65 storeys – though there are plans for one nearby that would reaches 76 storeys.
London dominates in the high-rise homes market, with four times the national average of residential towers – the English Housing Survey shows that just over half of homes built in London since 2002 are flats in high-rise buildings.
Consider MVHR ventilation from the early stages of design to help future-proof buildings
Mike Egan Business Development Manager
An upward trajectory
Even more significant is the fact that this trend is going to continue, driven largely by the UK’s booming build-to-rent sector where urban high rise developments dominate. Other cities including Cardiff, Bristol and Glasgow also have high-rise plans in hand.
It’s a popular approach with developers because it optimises land use in tight spaces and delivers in-demand accommodation for younger tenants who want to be near work and amenities – as well as providing operators with financial efficiencies.
The build-to-rent sector has also been keen to adopt sustainable features. High levels of insulation, use of low-carbon materials and electric heating systems, particularly heat pumps are increasingly common.
A lot of hot air
But there are challenges in delivering this type of accommodation. Air tight high-rise buildings are highly prone to overheating. And as new dwellings they must meet the requirements of Part O of the Building Regulations on mitigating overheating. This means keeping overnight temperatures to a maximum of 26oC.
It seems odd to think that homes in the rainy and cloudy UK could be prone to overheating, but climate change means that we are now much more likely to experience hot, dry summers with the prevalence of heatwaves rising even faster.
The heat island effect, which sees heat trapped by the tarmac and concrete of city centres and released at night, makes this even more likely in the locations where high-rise homes are so popular.
Part O, and its related calculation methodology CIBSE’s TM59, point to the importance of passive measures for mitigating against overheating in new dwellings. These include natural shading (e.g. from trees) or external architectural shading. Openable windows and cross ventilation are also highlighted as important design factors.
Improving indoor air quality
However, many of these options are impractical in high-rise dwellings. Openable windows in highly glazed facades may not be safe on higher floors, and city-centre locations may mean occupiers have security concerns about open windows at lower levels.
Open windows can also let in outdoor pollutants from nearby roads. Cross ventilation can also be challenging to achieve consistently, depending on building orientation and design.
Mechanical ventilation can provide a useful solution in these circumstances. It not only reduces the peaks of temperatures during very hot weather but also provides reliable year-round ventilation and a healthier indoor environment.
One example is Mitsubishi Electric’s Lossnay mechanical ventilation with heat recovery (MVHR) system. This simultaneously extracts stale air from a building and supplies fresh, filtered air. And while doing this, the units will simultaneously recover valuable heat energy for optimum efficiency.
The benefit of MVHR is that it operates continuously, ensuring a steady and predictable flow of ventilation across the occupied space. Lossnay is also excellent for residential projects as it operates at ultra-low noise levels, so it is an ideal solution for apartments where comfort is key.
Additional cooling
In high-rise apartment buildings, lack of external shading means that some occupied areas may be challenging to maintain at the required maximum temperatures in hot summers. A south facing, highly glazed apartment is high-risk for overheating.
With this in mind, Mitsubishi Electric has developed a Cooling Unit for the Lossnay system. It’s a self-contained product, with no outdoor unit required. An interface controller sits between the Cooling Unit and Lossnay to handle temperature sensing, speed, capacity and mode so it operates automatically.
It can be fitted in apartments most at risk of overheating, ensuring that occupants are protected from the impacts of overheating.
The critical factor for success in applying MVHR is to consider it from the early stages of design. It’s an ideal solution for new BtR project teams working to Part O alongside energy efficiency requirements.
What’s more, as high-rise residential developments continue to be an important option for housing in many cities, a good MVHR strategy can future-proof these buildings against rising temperatures, making them more attractive to tenants in the long-term.
Mike Egan is Business Development Manager
