HUMIDITY CONTROL


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Cost-eff ective humidity solutions explained


Evaporative humidifi cation and adiabatic cooling, while based on ancient principles can deliver signifi cant cost savings with a fast return on investment for a wide range of applications. Humidity Solutions managing director John Barker explains


I


t is no accident that so many town squares in hot climates include a fountain, which provides welcome cooling to local residents as they gather to discuss the issues of the day. Similarly, many Turkish houses are constructed with two chimneys. Water is sprayed into one of them, which causes the cooler, heavier, humid air to fall into the premises. This results in hot indoor air being ‘pushed’ up the other chimney, creating a positive airfl ow of cool air through the property. And, of course, there are many other similar examples around the world that make use of architectural or natural water features to provide cooling. Though the users of these relatively simple


cooling systems may not fully be aware of the underlying physics, they are enjoying what we now call adiabatic cooling. Adiabatic cooling occurs when liquid water evaporates (changes state) to form water vapour suspended in the air. Heat energy is taken from the surrounding air to provide the energy required for this change of state to take place. “The benefi ts of adiabatic cooling have been


known for thousands of years. It still makes sense to apply them to the control of temperature and humidity in our buildings” - John Barker These same principles have also been applied in modern buildings to provide a degree of local cooling, though historically the results have tended to be disappointing. However, with the application of modern technologies, the latest generation of evaporative humidifi ers off ers a more sophisticated, controllable and highly eff ective solution. In doing so, they help to address the common problem of low relative humidity (RH) in UK workplaces, while also providing ‘free cooling’ to maintain comfortable temperatures and reducing the energy consumption of comfort cooling systems.


Evaporative humidifi ers and bacterial growth


In modern evaporative humidifi ers, water is supplied to the top of the evaporative module and fl ows down wet media. Warm, dry air passes through the wet media, evaporates the water and thus raises the humidity level whilst also reducing the temperature. Latest models off er up to 12°C cooling as a


result of the transfer of energy when the water evaporates.


24 July 2025


Left: John Barker managing director, Humidity Solutions


The medium used for this needs to be of


inorganic fi breglass, so it does not provide nutrients for bacterial growth and is also incombustible. This latter property was an important consideration in choosing a humidifi cation solution for a project in the accommodation block on an off shore oil rig. Such systems can also be supplied with a variety


of diff erent thicknesses of media to allow for diff erent effi ciencies of the system – the deeper the media, the greater the effi ciency (higher humidity) that can be achieved. Cost-eff ective and hygienic, evaporative


humidifi ers are therefore a solution for many low- energy buildings, particularly when humidifi cation


and cooling are both required in the space. Obvious examples include data centres and a wide range of industrial applications where process machinery produces excess heat and precise humidity control is required.


Fitting adiabatic to air handling units (AHU)


Despite the clear benefi ts of humidity control and adiabatic cooling, many air handling systems are not fi tted with humidifi cation when they are fi rst installed. However, with the right equipment, retrofi tting to an existing air handling plant is


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