Significant energy savings can be achieved if humidification systems are specified and installed correctly, as Lindsey Henderson explains.
Maintaining a relative humidity of between 40 and 60 per cent in an office contributes to a healthy and comfortable working environment, reduces the spread of infections, respiratory problems, dry eyes and static shocks.

Humidifying an office to a stable relative humidity of 50 per cent also allows the temperature of the building to be reduced from, say, 23 to 21 deg C over the winter period. This can cut heating costs so that they equate to far more than the cost of installing and running a humidifier in the first place.

So why is this temperature reduction achievable? Most people are not used to relating to low humidity, whereas we are all aware of the temperature surrounding us, whether it is too hot or too cold. At low relative humidity moisture will be drawn from all surroundings and that includes the building occupants. This evaporation process of moisture from the skin causes us to feel cold, often leading to complaints from the occupants of feeling uncomfortable and cold putting pressure on the building operators to turn the temperature up to compensate for this.

The increase in running cost at this higher temperature over winter equates to valuable energy that need not be consumed.

On top of this, we often also see specifications that demand that a space should be left for humidification to be added at a later date if needed. Once the building has run for a short period, it is found there is indeed a need for humidification, but the space left restricts the selection of the humidification system.

Less energy efficient system

Where it could have been possible in the first instance to use a low energy option (maybe including water treatment to allow the building to save energy, conserve water consumption and maintenance requirements), humidifier suppliers are often forced to select a less energy efficient system due to the size of space left. This can cost the client far more in the long run throughout the life of the building.

As well as office applications there are many applications both within the hvac sector and manufacturing and process industries where adiabatic humidification can be used to humidify and also supply free cooling.

In direct air applications and, indeed, data halls for example, where the return air or space air temperature is high due to the heat gains from the production process and or equipment, using an adiabatic humidifier for humidification and cooling is an energy efficient way of controlling the environment.

Each application needs to be looked at as an individual case. However, if designed correctly, it is easy to humidify in the winter (ensuring good control and building efficiency) and benefit from free cooling in the spring and summer months. Up to 13 deg of cooling can be achieved and this dramatically reduces the duty (and therefore costs) of mechanical cooling.

The reason for abandoning humidification as the project progresses is often financial and linked to concerns about the energy running costs and maintenance of a humidification system. However, today's technology gives us many options for humidification system design.

Gas-fired humidifiers are an efficient option in applications where it is necessary to use steam due to the psychrometric design of the air conditioning system. The big benefit of these units is that they have large outputs and can be used where, in the past, several humidifiers may have been supplied to achieve the correct humidification duty. With their larger outputs, a healthy return on investment can be achieved.

Adiabatic humidifiers, which cover high pressure spray systems, compressed air and water spray systems as well as evaporative humidifiers, are becoming more common due to their low running costs and the benefits of free cooling.

These factors make adiabatic systems an attractive option in order to achieve low energy and efficiency. Issues relating to the hygienic operation and maintenance requirements were addressed long ago.

With the current drive to produce the most energy efficient buildings, now is the time for designers and building operators to consider humidification an important part of the air conditioning system and look at the benefits of including it within the specification from the outset instead of eliminating it as another few kilowatts of energy that can be saved.

If we humidify a building correctly to a comfortable relative humidity of, say, 50 per cent, the temperature within the building can often be reduced by 2 to 3 deg C.

This reduction in temperature can result in large savings in energy consumption, cost and produce a far more efficient building, precisely what we are all striving to achieve.

Every aspect of the building design should be looked at to ensure humidity control and or 'free cooling' are considered. The design should take into account lifecycle costs, correctly designed and controlled systems giving the most energy efficient solutions for each application.


• Lindsey Henderson is technical director of Humidity Solutions