HEATING, VENTILATION & SERVICES 57 Focusing on breathing
Ian Rogers of Gilberts Blackpool explains the importance of balancing ventilation with carbon reduction strategies in order to achieve the right air quality for users.
B
reathing – it’s essential to life not only for humans, but for buildings too. In the drive towards reducing
greenhouse gases, achieving the top standards of BREEAM, LEED et al, it is crucial that all involved in the building design – new build and retrofi t or refurbishment – remember that crucial fact. We focus on ‘building tight,’ to prevent the fortuitous air – and therefore energy – leakage, but ventilation is critical, for the health of the building, its occupants and its equipment.
It is a point emphasised in a new report by the National Engineering Policy Centre. Led by CIBSE, the Royal Academy of Engineering and the Institute of Mechanical Engineers, the report stresses that healthier, more sustainable spaces come from balancing insulation and ventilation. To many, it seems contradictory when designing low or zero carbon schemes, where the very ethos is about minimising heat loss, that we need to focus on letting fresh – therefore, cooler air – in. The keys are balance and control – choosing solutions that optimise energy effi ciency while maintaining healthy, compliant indoor air quality (IAQ), that remove damp, condensation and airborne pollutants without removing too much heat. It’s easier said than done, as we are constrained by the fact that 80% of our existing buildings will still be in use by the net zero target date of 2050, and, with the rising price of land, we are increasingly building upwards. The taller the building, the greater the variation of air pressure – a fundamental of ventilation – and thus greater air movement within as warm air naturally rises. That means greater potential energy use – and carbon creation – in controlling the internal environment. It is self-evident that the ‘greenest’ ventilation is natural. It uses no energy, relying solely on natural air movement principles to function. It is, after all, how two of our most iconic buildings – Hintze Hall at the Natural History Museum and
ADF MARCH 2025
Natural ventilation in the Natural History Museum’s Hintze Hall – refurbished by Gilberts
the Houses of Parliament – were ventilated when originally designed. But it requires much care at the design stage to balance the air paths and air fl ow.
Hence the evolution of hybrid ventilation. It centres around stand-alone natural ventilation for each space or zone, complimented by an ‘as and when needed’ mechanical boost, usually via a low energy fan. The system works by mixing the incoming fresh air with the warmer internal exhaust air to maintain compliant IAQ in each stand-alone space. The fresh air is drawn in through the facade at high level, and exhausted through the same route, once natural air movement principles have circulated the air throughout the space. Most systems can be tailored to individual specifi cation by the inclusion of LPHW heat coils, connected to heat pumps and additional fi ltration.
It is even possible to adjust the system to run on 100% fresh air, using the optional heat coil to temper the incoming air temperature. Using the heat coil also eliminates the need for radiators, which optimises usable fl oor space, reduces
Natural ventilation requires much care at the design stage to balance air paths and air fl ow
BREEAM Very Good was attained at the renovated India Buildings in Liverpool, with concealed ventilation
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