Specification of ventilation strategies is experiencing a period of flux post-COVID. The Government’s COVID approach – reinforced by recommendations from the Health & Safety Executive at the time – was to open windows as much as possible. However, whilst this maximises fresh air, it also allows in pollutants, cold or overly warm air and noise; not ideal for a working, energy control, healthcare or a stable learning environment.
And as we return to the office, architects face new pressures on how to design and refit those spaces to satisfy all the above demands and give workers peace of mind – whilst creating an architecturally-stimulating environment.
However, there are other forces at play beyond COVID, most critically the human effect on the planet and the need to reduce our carbon emissions. Buildings are, after all, one of the biggest contributors towards the UK’s carbon emissions. Yet data prediction maintains that most of the buildings that will be used by 2050 – ‘target date net-zero carbon’ – are already constructed.
Also, now increasingly in the mix is the consideration of health and wellbeing for the building occupants. The Building Regulations Part F (Ventilation) and Part L (Conservation of Fuel and Power) were already under review before the pandemic, with the revisions just coming into force (June 2022). During that time, the NHS similarly reviewed its guidance on ventilation (Health Technical Memorandum 03-01), which, at the time, instigated to help address the health estate’s carbon emissions/footprint but, coincidentally, also reviewed ventilation in terms of the spread of infection. Likewise, CIBSE (The Chartered Institute for Building Services Engineers) published new guidance for commercial buildings.
The issues are interconnected. What does this all mean for architects?
The common denominator
The overriding common denominator is indoor air quality (IAQ) – optimising fresh air and filtration. The issue architects face is how to do that energy efficiently for the health and wellbeing of the buildings, the occupants and the planet.
The new Building Regulations Approved Document F recommends as best practice increased ventilation rate – of 10 litres/second/person or 1l/s/m2 floor area, whichever has the higher rate – and inclusion of CO2 monitors to maintain good IAQ.
Natural ventilation evolution
Natural ventilation would logically be the preferred solution, especially when adequately designed in and removing the human element of opening windows, with the secondary issues this brings. It is, after all, the original form of ventilation and uses only physics and natural air movement to function.
But, however well you design a building, it may not always be possible or practical to include natural ventilation in a compliant way. Whatever the intended use of most buildings, they need to be zoned/compartmentalised inside to deliver the required areas for specific activities, be it work, play, healthcare etc. The alternatives are mechanical ventilation or hybrid.
Mechanical ventilation evolution
Mechanical inevitably requires energy consumption. However, the advent of low-energy fans, heat recovery and low-pressure technology are all playing a part in helping mechanical ventilation remain a valid option.
Equally, the means of supply and exhaust of conditioned air is evolving, giving you a whole new array of tools to explore in your designs. Swirl diffusers are a case in point. They adjust airflow depending on the internal and supply air temperatures without supplementary energy/power. They cleverly provide rapid entrainment and mixing, harnessing physics principles to achieve a stable, comfortable internal environment, whether warming or cooling is required.
Swirl diffusers have value from an architectural perspective too. With the trend towards exposed ceilings, specifiers have unwittingly created a ventilation problem. Fresh air discharges from the inlet and ‘dumps’ onto people below, rather than dispersing along the now-missing ceiling and intermixing with the existing air. The solution is simple – a coanda plate. Added to the swirl diffuser, it creates a tiny surface (ceiling) that is just enough to make the correct air circulation pattern. The coanda can be almost any design, shape, size or material you like – we’ve even manufactured backlit acrylic versions.
Thermally-controlled diffusers – aka jet nozzles – deliver omnidirectional, rotating warm air in the vertical, and cool air in a horizontal direction, thereby eliminating draughts whilst providing rapid and efficient initial warm-up and eliminating potential cold spots at a low level.
Hybrid ventilation evolution
The Education & Skills Funding Agency, when it revised Building Bulletin 101, was ahead of its time, advising hybrid ventilation as the most effective means of ensuring adequate ventilation and IAQ whilst addressing increased energy usage.
Hybrid ventilation centres around stand-alone natural ventilation for each space/zone, complemented by an as-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.
Most systems can be tailored to individual specifications by including heat coils and filters. 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. This keeps a cleaner and safer environment whilst ensuring indoor temperatures are not compromised, thereby avoiding cold draughts without needing to boost heating systems to maintain internal comfort levels. Using the heat coil also eliminates the need for radiators, optimising useable floor space.
Hybrid systems are easily configured to work with heat pumps, utilising that energy source to provide managed ventilation for each space. As solely ventilation, they cost as little as £5/space/year to run; even when serving as the heating, the cost is increased by only £2.19/space/year.
The way ahead
With a little thought, it is possible to achieve the perfect balancing act of good ventilation, good air quality and low/no energy for ventilation within an airtight building.
The trick for architects going forward is to work with experts – building services consultants and, ideally, manufacturers. Working with such complexities daily, they have the in-depth knowledge to guide you. You can then be sure that the systems you specify are as energy efficient and environmentally friendly in all aspects as possible. You will still deliver the desired aesthetics with the appropriate internal air quality and comfort.
