– David Simkins, director of industrial services at Polygon US Corporation (www.polygongroup.us), says:
It’s a dilemma faced by numerous facility managers every year: sweltering heat exists outside, the building is becoming besieged with moisture inside and productivity is suffering.
Too much humidity can produce a host of problems. For example, processes can be delayed or even stopped completely, machinery and electrical switch stations are liable to failure, and working conditions can become increasingly difficult. High seasonal humidity periods can over-tax an HVAC system, causing slowdowns or shutdowns, and the resulting loss of productivity, costing thousands of dollars. In addition, inventories can suffer moisture gain while in storage, mold can form, freshness or product appeal can suffer, packaging can deteriorate, and equipment can corrode. In addition, condensation causes corrosion of metal surfaces, such as the roof and beams, that can significantly reduce the life of the structure.
First, it’s important to understand why such problems are so prevalent in the warm summer months. As temperatures and humidity levels outside a facility significantly increase, it becomes more and more difficult to maintain relative humidity (RH) inside the building. The reason? Often, the temperature needed to maintain a low moisture level using conventional HVAC equipment exceeds the capacity of the installed systems.
What can one do to ensure business continuity when high temperatures and humidity are wreaking such havoc?
How to Maintain Effective Moisture Control
Desiccant dehumidification technology is the most effective method for maintenance of proper humidity levels in the hot, humid summer months. Using dehumidification on a temporary basis is a smart short-term solution and also gives building managers the practical knowledge to build an efficient, permanent solution.
While mechanical refrigeration dehumidification can keep humidity at relative levels, it does so at a higher cost of operation and maintenance than other methods, specifically desiccant dehumidification. A mechanical system needs to sub-cool and potentially re-heat to achieve significant dehumidification. This process is very energy-consumptive and limited to the freezing point where the cool coil frosts and becomes a block of ice. Most mechanical dehumidification systems have low ambient control and will not operate below 45º.
Many facility owners have discovered that desiccant dehumidification can more cost-effectively solve the humidity problems in a building, provide a more comfortable environment for workers and improve product quality by removing unwanted moisture.
Desiccant dehumidifiers eliminate fog, condensation, and mold and mildew while reducing operating expenses. Desiccants allow facility managers to run fewer compressor hours while reducing condensation in the building, which also has a potential savings in structural repair and painting. The desiccant system maintains superior indoor air quality without sacrificing system performance.
Another major advantage is the ability to deliver very low dew points necessary due to the high ambient temperatures and moisture experienced during summer. The system achieves lower dew points because the desiccant removes water in the vapor phase and is not limited by temperature. It removes moisture continuously without needing a defrost cycle.
In the past, refrigeration cooling/re-heating units in a particular facility were not equipped to condition fresh air required under today’s building codes. Now, outside air is requested by current codes, such as BOCA 93, ASHRAE 62-89, that require central treatment of fresh air to meet the intent of the Indoor Air Quality Act.
Typical HVAC systems use cooling coils to control humidity. That approach has limited capabilities and can cause many problems. Humidity cannot be controlled independently of temperature, so cooling-based dehumidification can result in over-cooled, clammy buildings during spring, summer and fall. This approach cannot maintain the low dew points required to optimize the energy usage of the refrigeration system. Overflowing drain pans and saturated ducts result, promoting biological growth that can lead to health problems.
For example, in an ice arena, the energy peaks of the refrigeration system generally occur simultaneously with the peak outdoor ambient. This adds to peak demand charges and an increase in operating costs for rink operators. Using a less expensive natural gas desiccant dehumidification system can solve this problem.
To illustrate that point, a recent Concord, Mass., facility study that compared mechanical and desiccant dehumidification in an ice rink operation revealed an immediate improvement in humidity upon desiccant dehumidification installation and implementation. Conditions before activating the desiccant dehumidifier were 43º and 96% RH inside the facility. Six hours after initiating the desiccant dehumidifier, the temperature rose slightly and the humidity lowered to the desired set point of 50% RH. The dryer removed 800 to 1,000 pounds of water from the air. In addition, the rink enjoyed a total monetary savings of $12,000 to $15,000 during summer season by reducing refrigeration run hours for the ice sheet and the mechanical heating and cooling systems.
Steps to Consider
No matter the type of dehumidification system used to maintain relative humidity in a facility, attention to other important can help maintain good moisture control during the summer months, and keep maintenance and operation costs from skyrocketing with the change of seasons.
Facility operators should conduct regularly scheduled maintenance. Regular surveillance of all HVAC and dehumidification equipment is crucial. The units need to be balanced and operating at 100 percent efficiency at all times. Don’t ignore the worn belts, high amp draw motors and warm bearings because those will be the weak points of the system when the heat and humidity return.
Keep the facility well-sealed. Ensure doors leading to the outside do not remain open. Tight weather stripping is important, as well as making sure there are no holes on the exterior of the building. Revolving doors instead of standard “open and shut” doors help reduce humidity levels. If building walls are constructed of cinder block, cover the porous surface with a coat of vapor-retardant paint to reduce the internal humidity load and keep the facility comfortable.
Reduce light. Light shining through walls and around windows and doors can cause moisture problems. If this is the case, seal in the area and minimize the source.
Reduce outdoor air. Outdoor air is required to meet IAQ standards, but it needs to be controlled. The best way to meet the standards and maintain control is through the use of a make-up air system coupled with a desiccant dehumidifier. An air quality sensor (CO or CO2) also is highly recommended. Monitoring the air in the facility is the most effective means of reducing operating cost while providing a quick response to the ever changing environment.
Abundant opportunities remain for use of temporary dehumidification technology in manufacturing, processing, and many other industries. Personnel would do well to consider its use whenever weather variations affect workers, production rates or product quality, when corrosion or condensation cause problems, or whenever product must be dried at low temperatures.