Balancing air quality and guidance with meeting energy and carbon reduction metrics can be a challenge. Ian Rogers from Gilberts Blackpool offers compliance advice
Designers and specifiers of HVAC are facing a raft of new, diverse issues to address, prompting a need to change the way we achieve good ventilation and therefore air quality within our buildings. Agile workspaces, reduced energy consumption, changing regulations are all playing a part.
The complexity is exacerbated by the fact that, alongside the prevailing drive to reduce a building’s carbon footprint and energy usage, more often than not we are dealing with re-fitting or refurbishing existing buildings: some 80% of the buildings that will be in use by 2050 are already constructed. Thus we are inheriting a design that has to be adapted, rather than creating a new solution from scratch.
Manufacturers have been working to improve existing or devise new products to support the changing building services environment. When properly designed, “accessorised” and integrated into a building, natural ventilation can often deliver the criteria needed today, especially when its latest derivative – hybrid ventilation – is employed.
With computer-based systems now available, such as BIM and CFD (Computational Fluid Dynamics), it is possible to virtually test any design before installation, to ensure appropriate levels of ventilation – now at least a minimum 10 l/s/p – is achieved along with appropriate filtration, to achieve the Health & Safety Executive’s <5000 ppm long term.
According to the RCIS, demand for offices is on the increase – up 30% in 2022. The offices of the future need to be agile and increasingly are open plan to achieve that flexibility of use and occupancy. Whether new build or refit, hybrid ventilation is a great way to tick all the boxes in terms of ventilation levels, sustainability and indoor air quality (IAQ).
Hybrid ventilation centres around stand-alone natural ventilation for each space/zone, complimented by an as/when needed mechanical boost, usually via a low energy fan. It mixes incoming fresh air with 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.
Being at high level, and the fresh air tempered as it is drawn into the interior space, there are no cold spots or draughts, optimising occupant comfort.
Most systems can be tailored to individual specification by the inclusion of LPHW heat coils, connected to heat pumps and additional filtration. It is even possible to run on 100% fresh air, using the optional heat coil to temper the incoming air temperature. This keeps a cleaner and safer environment while ensuring indoor temperatures are not compromised, thereby avoiding cold draughts without the need to boost heating systems to maintain internal comfort levels. Using the heat coil also eliminates the need for radiators, which optimises usable floor space.
Even if mechanical ventilation is used in office space, a little careful thought in the design of the way the air is delivered into – and exhausted from – the interior can optimise use and flexibility of floor space. Linear bar grilles located around the perimeter, swirl diffusers in an exposed ceiling or raised floor are some examples.
Coinciding with Covid, but driven by the need to reduce energy consumption and cost (running at around £0.5bn per year), HTM guidance in the healthcare sector was updated to require natural ventilation to be the default, with mechanical ventilation as a last resort.
In such environments, the air movement paths need to be different, particularly in operating theatres where the air needs to “wash” over the patient on the table and flow away at low level to effectively remove airborne pollutants or particulates. Software modelling is crucial to validate any design in such a sensitive environment.
Schools too are also an increase in building, and the latest Building Bulletin 101 guidance recommends hybrid ventilation as the most appropriate solution to balance IAQ and sustainability.
The trick for architects, going forward, is to work with experts such as building services consultants, and, ideally manufacturers. Working to balance such complexities on a daily basis, they have the in-depth knowledge to guide specifiers. Architects and other consultants can then be sure that the systems are as energy-efficient and environmentally friendly in all aspects as they can be. The desired aesthetic can still be delivered, but with the appropriate quality of internal air and comfort.
Ian Rogers is sales director at Gilberts Blackpool