HUMIDITY CONTROL
www.heatingandventilating.net
Right: Dave Marshall- George, UK & Ireland sales director at Condair
However, due to their size, they’re viable only for projects requiring 40kg/h or more, making them unsuitable for many small-to-medium offices. For offices without centralised HVAC, direct
Enhancing office productivity with humidity
Dave Marshall-George, UK & Ireland sales director at Condair, looks at why and how to manage humidity in commercial offices
I
n the modern commercial office, managing indoor humidity is more than just a comfort or regulatory issue - it’s a productivity imperative. While there’s no statutory regulation mandating specific humidity levels, multiple authoritative bodies recommend a mid-range of 40–60% RH. Maintaining humidity at this level improves health
and reduces absenteeism. Viruses like influenza and SARS-CoV-2 are less stable and less transmissible at mid-range humidity. Dry air allows respiratory droplets to evaporate quickly, turning them into aerosols that linger and travel further. Proper humidity encourages droplets to fall, reducing infection risk. Studies also show that at mid-range humidity, the respiratory immune system combats infection more effectively, lowering cross-infection potential.
Beyond respiratory health, humidity affects
comfort and cognitive performance. Dry air can cause skin irritation, dry eyes, and respiratory discomfort, distracting employees and reducing concentration. Research shows that balanced humidity improves focus, reduces headaches, and lessens fatigue - a win for wellbeing and productivity. In the UK, indoor humidity typically drops below 40% RH in heated offices from October to March, coinciding with flu season. Without adding moisture, indoor humidity depends on outdoor air and heating. Even when cold outdoor air has high relative humidity, heating it to 20°C indoors drops humidity below the healthy threshold.
How to Humidify
There are several approaches to humidifying office spaces, suited to different building designs, HVAC configurations, and operational needs. If a building has a centralised air handling system, it’s typically used for humidification rather than in-room units. Steam humidifiers are most common, easy to install on air handling units and flexible for retrofitting. They use electricity or gas to create steam, though electric is now the “green” solution when powered by renewables. Adiabatic humidifiers offer very low energy use when paired with heat recovery systems for pre- heating. They also reduce maintenance, as scale from evaporation is washed away during operation.
12 December 2025
room humidifiers are a good solution. Mobile units can provide up to 2kg/h of humidity and can be plumbed-in or manually filled. Steam humidifiers can also be used in-room with blower packs for capacities up to 30kg/h, though larger units may not suit busy office environments due to their industrial size. For larger office areas, high-pressure spray humidifiers offer discrete, scalable control. A central pump system pressurises water and distributes it to spray heads in humidified zones. Zone control allows outputs to vary by area needs, ensuring balanced humidity. These systems start at around 30kg/h, with a single pump station capable of up to 800kg/h - ideal for medium to large offices.
Energy Concerns
Even when the need to maintain humidity is recognised, the operation of humidifiers in commercial offices can be overlooked due to the drive to minimise energy use. Humidification, like any building service, does require energy and therefore has a cost to the building operator. Strategies to reduce humidification energy include using humidity recovery systems on exhaust air ducts, and simply operating less frequently, whilst staying above the 40%RH health humidity threshold. This can be done by reviewing the hours of operation, ensuring humidity levels are only being maintained as and when the building requires. Or by using a humidifier with a more accurate level of humidity control and lowering the overall set-point. For example, electrode boilers, which control to +/-10%RH, would need to be set at 50%RH for the environment to always remain above 40%RH. Whereas resistive steam humidifiers can control to +/-2%RH and could therefore be set at 42%RH. This would mean they operate less frequently, use less energy but still maintain a healthy humidity. Ultimately, the cost of humidification should be justified by its return on investment—reduced absenteeism from fewer respiratory infections and increased productivity from a better working environment. If this correlation were clearer to building operators, skipping humidification to save energy would never be an attractive option.
www.condair.co.uk
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