The remediation industry has long relied on traditional equipment like mechanical dehumidification and desiccant systems for the removal of excess moisture from flooded and fire damaged buildings. In many cases these are the better choice for drying out the high moisture situations in preparation for later renovations. Still a controversy persists whether or not air conditioning can be used as effectively as a dehumidifier. The answer is most definitely yes, but it depends on the unit type and application.
But moisture removal is only one of the reasons why portable air conditioning should be a serious contender for remediation projects. Just as important as moisture removal is space conditioning during the renovation phase of the project.
How Mechanical Dehumidification Works
Portable air conditioning is not just for cooling outside tents and temporary facilities. When the right type of portable air conditioner is used, it will not only dehumidify the facility, it should also be used to condition the space for the repair phase of the project.
In simple terms, dehumidification is the removal of water vapor from the air. This is accomplished by lowering the air temperature to its dew point, where it condenses and can then be removed.
Efficient dehumidification relies on two basic concepts. First, the air must be chilled as low as possible in order to effectively remove the moisture that is in the air. This is done through the refrigeration cycle of both dehumidifiers and air conditioners. Air is cooled as it passes over a cooling coil and a drain pan captures the moisture from the air as it condenses on the coil.
Second, the ambient room or space temperature should be raised as high as practical so that it can absorb the maximum amount of moisture from the space. This is accomplished by reheating the air as it returns to the room, and is done differently by air conditioners and dehumidifiers. This cycle continues until the space has reached the desired temperature and humidity levels.
Dehumidification Versus Air Conditioning Systems
A key difference between dehumidifiers and air conditioners is how the heat from the refrigeration cycle is processed. Dehumidifiers use the heat generated by the refrigeration cycle to immediately heat the air re-entering the space. This results in dry, warm air leaving the unit.
Air conditioners, on the other hand, reject the waste heat away from the space, usually to an external air-or water-cooled condenser. The conditioned air is returned to the space dry but cooler.
Since maintaining a warmer ambient is important for dehumidification, good quality portable air conditioners are available with supplemental electric heating coils or in heat pump models to reheat the cooler, dry air. The temperature can be controlled very accurately for efficient dehumidification, and the availability of heating and/or cooling can be used during the reconstruction or renovation phase.
Another key difference between dehumidification units and air conditioners is the way they control sensible and latent heat. Sensible heat is essentially the air temperature within the space and latent heat is the additional heat in the form of moisture in the air, the relative humidity (RH).
An air conditioner measures and controls temperature, cooling the space until the thermostat reaches its set point. A dehumidifier removes moisture until the humidistat reaches the desired RH level.
The sensible-to-latent heat removal ratio for a dehumidifier is 50-50 while an air conditioner is closer to 70-30. In other words, dehumidifiers ring out more moisture, but they generally have poor to no control of space temperature. Air conditioners have great control of space temperature but remove moisture at a lesser rate.
Which System Is Better?
If your only interest is maximum moisture removal in the shortest time, straight dehumidification is probably the better choice. But when moisture removal is lower and the space will require renovation or some type of post construction, a portable air conditioner should be your number one selection.
Portable commercial air conditioners can easily reach 2,000 CFM for a five-ton unit when in the cooling stage. However to improve the moisture removal characteristics, lowering the fan speed by up to 50% improves its dehumidification performance. By slowing the warm, moist room air traveling over the cold evaporator coil, additional moisture can be removed.
Portable air conditioners are available in a variety of configurations and sizes as high as 30 tons for even the largest of buildings. Smaller units can have wheeled bases making them easy to transport and position, and their narrow cabinet design will pass through a standard 3/0 door opening without modification.
The Additional Benefits Of Portable Air Conditioning
The key to any job site is to maintain Indoor Environmental Quality (IEQ) during reconstruction and renovation. Portable air-conditioning systems offer the restoration and remediation industry an excellent tool to assist in the safe and efficient completion of restoration projects.
It’s commonplace during renovations to seal the affected area by turning off the air conditioning and isolating the airflow from the rest of the building. The goal is to maintain a negative pressure in the workspace (or positively pressurize other areas) to prevent the migration of air contaminants from work areas to occupied areas.
Portable air conditioning units will retain a controlled environment by maintaining specific relative humidity and temperature conditions, and they can also effectively filter the circulated air. That means the same unit that removed the initial moisture can be used to provide an ideal workspace environment. Worker productivity is maximized and space conditions are improved through dust control.
Conditioned space is also critical for building materials and finish applications. The installation of hardwood floors and wood paneling require the materials be normalized at the right temperature and humidity to prevent warping or later expansion/contraction.
Controlled humidity will protect metal surfaces from oxidizing and help wall coatings dry faster and more completely. And renting a single unit for moisture removal and space conditioning is generally less expensive and requires less set up time.
Equally important is the prevention of mold and fungus. Molds like Aspergillums can grow on modern building materials such as gypsum board and ceiling tile if they are allowed to remain wet more than 72 hours. Spores become airborne during repair and/or disturbance of the building and have low settling velocities, remaining in the air for long periods of time. A portable air conditioner will continue to dehumidify the space and filter the return air as long as the space is being conditioned.
Selecting the Portable Air Conditioner That’s Right for Your Application
Portable air conditioning units are available in a variety of sizes and configurations while purpose-built dehumidifier units available through rental distributors are generally small in capacity. As an example, quality manufacturers like United CoolAir Corporation offer one of the largest selections of portable systems and capacities capable of conditioning even the largest of commercial spaces.
Portable horizontal air conditioning systems are the most popular and have the widest range of sizes and arrangements. These smaller horizontal units provide needed flexibility and can be used for indoor or outdoor installations.
Typical cooling capacities can reach as high as 15 tons and include the option for electric heating. Since mobility is paramount for these units, they are narrow in design to navigate doorways and entrances and include integral unit-mounted forklift pods or casters for easy mobility.
For the really large projects or where it makes sense to replace multiple smaller systems with a single unit, consider a larger, high capacity system. With sizes ranging up to 30 tons of cooling, these units can also be equipped with up to 80 kW of electric heating. Narrow in design, they are easily positioned using the built-in lifting pods and can be stacked if necessary. Trailer-mounted units are also an option for outside installation.
Also available are vertical portable air conditioning and heating units. While not as popular as the horizontal models, they offer both bi-directional free blow and ducted operation and find great application in large open spaces.
Typical sizes can range from three to 30 tons with up to 60 kW of heating. These narrow footprint units are easy to transport and move into position using the forklift pod. Installation can be inside or out as conditions allow.
With the right manufacturer, you can select from standalone in-line blowers and heaters that work in conjunction with larger tonnage portable air conditioners for more reheat capability and longer flexible duct runs.
Today’s portable air conditioners are easy to install with features like Camlock power connections, duct collars, built-in circuit breaker and more. Many include multiple ducting options with high static pressure for long duct runs. Quality units are also equipped with an internal thermostat and offer an option for remote control if required.
Always choose a reputable portable air conditioning brand with a proven track record of performance. They are your number one source for getting a unit that best fits your application. But not all portable air conditioning units are built to the same standards. It is not uncommon to find traditional building air conditioners, or even rooftop designs, adapted in some fashion for portable use. These units are built for stationary installation and cannot withstand the continuous movement and transportation requirements necessary for portable equipment. When used in portable applications, they are prone to refrigerant leaks, component failures, and reduced life expectancy.
Finally, it’s also important to evaluate the suppliers of portable air conditioning rental equipment available in your area. While most will be helpful in getting you started, choose one that will help you select the right size, type of equipment and accessories for your application.
Be sure to ask about technical support in the event of a malfunction, and if they carry an inventory of equipment should it be needed quickly.