Heating and Ventilating

The practical problems associated with installing humidification equipment have limited the options available... until now, says John Barker
Offices, call centres and museums all require a stable humidity for occupants or artefacts, but until now the practical problems associated with installing humidification equipment have limited the options available.

Modern buildings are often virtually sealed to prevent expensive energy losses. This means that little outside air enters the building, often resulting in the supply air duct into the back of the fan coils being small in diameter and unheated. This makes it difficult to position a humidifier steam lance and the air is incapable of transporting enough moisture to ensure a comfortable humidity in the space.

Many buildings suffer from poor humidity levels because of naturally low moisture levels in winter and cooling stripping the moisture out in summer.

This can cause considerable discomfort and can cause dry eyes, sore throats, headaches, respiratory problems, unpleasant static shocks and the spread of viruses.

The Chartered Institution of Building Service Engineers (CIBSE) recommends humidity levels of 40 to 60 per cent rH for general comfort conditions. Other guidance comes from the EU Directive on Display Screen Equipment which recommends humidity control for people working at computer workstations.

What are the options?
So, we have identified the problem with low humidity in buildings, but what options do you have?

Traditional solutions would be to mount electrode steam boilers on the walls around the office or to wheel in mobile humidifiers. Both have limitations - steam humidifiers are high energy users, unattractive and require a hot water drain. Mobile units take up floor space, have low output and must
be manually filled with water.

In my view, atomising nozzles provide the most practical and energy efficient way of creating the stable environment required in workplaces. They offer several advantages.

For example, the heads are virtually silent in operation, they offer good moisture distribution and zone control off one centrally located pump promotes ease of installation. All this is provided with an extremly low power requirement and therefore running cost (under 1.5kW for the whole building compared to 70kW for a steam humidifier producing 100kg/hr of moisture).

The low maintenance and spares requirements of the system and its whole netlife cost beat other systems, providing an attractive payback time for refurbished offices as well.

By humidifying directly into the space, the true effect of the humidity will be felt on the floors, eradicating the dry air issues.

It has been proven that once a building is effectively humidified you can often reduce its temperature, cutting running costs.

Direct room spray humidifiers also offer benefits in the summer as the spray has a cooling effect, reducing the load on mechanical cooling. This all helps reduce the environmental impact of the building.

The incoming water supply in direct room spray units is via a reverse osmosis system to prevent mineral dusting in the space and ensuring minimal maintenance from mineral build up. UV sterilisation adds additional protection to water flowing to the high efficiency pressurisation pump.

A typical system provides water at 50 bar to humidification heads which incorporate a small fan and nozzle. The fan draws warm, dry air directly from the office space past the nozzle, generating micro-fine atomised water. This ensures fast and effective evaporation of the moisture directly humidifiying the space.

The heads are grouped in zones and are controlled by sensors which keep the relative humidity constant in each area, while all zones are supplied from one central variable speed pump.

Easy access for maintenance
The central plant is mounted away from the humidifiers, typically in a plant room or service area. This allows easy access for maintenance without disruption within the space.

Nozzle heads are mounted on columns or walls within the space with the number of nozzles required depending on the humidity duty required.

The pressurised water is concealed above a false ceiling run in micro-bore hosing, reducing disruption within the space. On top of this, only the nozzle heads are visible in the offices.

// The author is sales director of Humidity Solutions //