COVER STORY Improving office productivity with humidity I
Dave Marshall-George, UK & Ireland sales director at Condair, looks at why and how to manage humidity in commercial offices
n the modern commercial office, managing indoor humidity is more than just a comfort or regulatory issue - it’s a productivity imperative. Even though there is no single statutory regulation that mandates specific indoor humidity levels for offices, multiple authoritative bodies recommend a mid-range of 40- 60%RH.
Maintaining humidity at this level in a commercial office will improve health and reduce absenteeism. Viruses like influenza and SARS-CoV-2 are less stable and less transmissible at a mid-range humidity. Dry air allows respiratory droplets to evaporate quickly, turning them into lightweight aerosols that linger longer and travel further. Proper humidity encourages droplets to fall to the ground, reducing the risk of infection. Studies have also shown that in a mid-range humidity, a person’s respiratory immune system combats infection more robustly, further reducing the potential for cross-infections. Beyond respiratory health, humidity affects comfort and cognitive performance. Dry air can lead to skin irritation, dry eyes and respiratory discomfort, all of which can distract employees and reduce concentration. Studies have shown that people working in environments with balanced humidity levels report better focus, fewer headaches and less fatigue, a win for both employee wellbeing and business productivity.
In the UK, indoor humidity will typically drop below 40%RH in heated offices from October through to March. This period corresponds very closely to the UK’s flu season. Without proactively adding moisture to the indoor environment, a building’s indoor humidity is dependent on the condition of the outdoor air entering and any heating being applied indoors. Even when the cold outdoor air has high relative humidity, after it has been heated to around 20°C inside a building, its humidity will drop below the healthy 40%RH threshold.
How to humidify
There are several approaches to humidifying office spaces, each suited to different building designs, HVAC configurations and operational needs. If a building has a centralised air handling system, it is typically used for humidification rather than employing in-room humidifiers. Steam humidifiers are most common, as they
are relatively easy to install on an air handling unit, and more flexible when retrofitting. They mainly use either electricity or gas to create steam. Although with the drive for carbon neutral, electric is now the “green” solution, as it offers a lower carbon footprint when used with energy from a renewable source. Adiabatic humidifiers offer very low energy humidification when used with heat recovery (HR) systems that provide the required pre- heating. They can also lower maintenance, as unlike steam humidifiers, much of the scale that is left behind from the evaporation process is washed to drain during regular operation. However, due to their size, adiabatic humidifiers are only really viable when projects require 40kg/h of humidity or more, so many small-to-medium office applications may not suit this technology. For offices without centralised HVAC systems,
direct room humidifiers offer a good solution for maintaining a healthy humidity. Commercial mobile humidifiers can be placed in a room and provide up to 2kg/h of humidity. They can be plumbed-in for convenience or manually filled. Steam humidifiers can also be used in-room with a blower-pack dispersing the humidity, if the capacity needed is up to around 30kg/h. Although at the upper end of this capacity, the size of the unit would not really compliment a busy office environment due to its industrial nature. For larger office areas, high-pressure spray humidifiers offer discrete and scalable humidity
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control. A centralised pump system treats and pressurises the water, which is distributed to a network of spray heads located in the areas being humidified. Zone control allows for outputs to be varied according to the humidity needs of the individual areas, which provides balanced humidification. High pressure spray systems start at around 30kg/h, and a single pump station could provide up to 800kg/h, so this technology can suit any medium to large office.
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. However, energy use aside, the on-going cost of humidification should really be justified by the return on investment from it. This return directly comes from the reduced absenteeism due to the lower level of respiratory cross- infection among staff, and the increased productivity from an improved working environment. If this correlation was more evident to building operators, not humidifying to save on energy would never be an attractive option.
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