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Getting hot under the urban collar


Andrew Nash, Nuaire residential divisional manager, looks at the modern urban issue of overheating and how ventilation manufacturers are stepping up to provide innovative solutions


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atest fi gures from the Offi ce for National Statistics have estimated 4,507 deaths in England in 2022 were linked to heat. That’s the highest number of estimated heat-related deaths over the last 35 years. The highest risk of death was in London on days when temperatures exceeded 29°C. What’s more, the government estimates that the average number of heat-related deaths in the UK will more than triple – to 7,000 every year – by the 2050s. Climate change is driving rising temperatures, but


this is compounded by building in already densely populated urban heat islands such as London, Manchester and Birmingham.


‘Dangerously unprepared’ for heat


Researchers from Oxford University have recently published an alarming report which places the UK in the top list of countries heading for dramatic increases in uncomfortably hot days if temperatures break the international 1.5˚C target. They forecast a rise of 30% in days when cooling will be needed. What’s worse, it places us in the top ten countries that are ‘dangerously


Left: Andrew Nash, residential divisional manager, Nuaire


unprepared’ for heat. UK Building Regulations, Approved Document O:


Overheating was introduced to provide guidance on mitigating overheating in new residential buildings. It places emphasis on minimising solar gains by limiting window areas, adding external solar shading, and stipulates larger window openings. However, even with these factored in, there may be some apartments or homes in a development where external factors such as noise or pollution restricts the use of window openings to ventilate away excess heat. In these circumstances, Approved Document O allows for mechanical methods and, when all else fails, cooling. Site-wide cooling solutions, whether chilled water


or refrigerant based, are only cost eff ective when the majority of plots require cooling. Split systems, whilst more applicable on a plot-by-plot basis, require unsightly external condensers.


Hybrid technology


As the phrase goes, necessity is the mother of invention, and new solutions are being developed. One of the latest to hit the market is based on mechanical ventilation with heat recovery (MVHR) systems, with the addition of a cooling module. How does it work? The technology might be sophisticated, but the principle is straightforward. The primary aim of MVHR systems has been to


recover heat which would otherwise be lost from air extracted from ‘wet rooms’ and use it to preheat incoming fresh air in winter, saving energy and reducing heating bills in the process. In addition to the usual ‘Summer bypass’ facility, Nuaire have added a cooling module containing a DX refrigerant circuit which reduces the fresh air supply temperature on the warmest of days. The module works in conjunction


VENTILATION


with ‘coolth’ recovery provided by the MVHR and unwanted heat from both elements is exhausted back to atmosphere.


The Hybrid Cooling System, formed by the


MRXBOX MVHR working with the cooling module, is automatically activated when the internal temperature exceeds 23°C (although this can be adjusted). It’s easy to install and the refrigerant circuit contained in the cooling module is ‘sealed for life’; if you can fi t an MVHR system, you can fi t this hybrid system without any extra training.


A cautionary word


Although cold remains the bigger killer in England and Wales (200,000 deaths related to cold since 1988, compared to 50,000 heat-related deaths), climate change is leading to increasingly uncomfortable – and dangerous – temperatures in our city homes. The Hybrid Cooling System is an innovative, practical and aff ordable solution to lower temperatures in problem areas of developments, where specifi c properties cannot be naturally ventilated and where site wide cooling technologies are not feasible. But the hybrid cooling solution makes no claim to be comfort cooling or air conditioning. It can however make a signifi cant diff erence to internal temperatures and, in doing so, help protect the health and wellbeing of occupants


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