Simply put, the goal of drying is to create rapid evaporation. Evaporation is the separation of water molecules created by the addition of energy to the water, and the absence of moisture in the existing air. There are three aspects to any environment that you can control and which make rapid evaporation occur: humidity, airflow and temperature. The most effective drying systems are those where all three elements are controlled.

Among drying professionals, humidity (H), airflow (A) and temperature (T) are commonly referred to as the drying pie and abbreviated as HAT. Each can be measured and evaluated in a number of ways, and each has a direct influence on the rate of evaporation that will occur when moisture and materials interact.

A common misconception is that adding airflow with fans or adding heat with the HVAC system – or both – will dry out a room after water intrusion has occurred. In reality, this typically isn’t enough. All three pieces of the drying pie should be considered in order to dry quickly and effectively, and to prevent further damage.

Adding airflow and/or heat may seem like it’s working, because surfaces appear to be getting drier. But you’re really just kicking up moisture into the air without actually removing it. This can actually lead to more damage, as moisture is added to other, unaffected materials.

Humidity plays an important role because the amount of moisture in the air directly affects the amount of moisture in materials. Humidity also influences the rate at which materials will gain or lose their moisture.

It is important to understand that the moisture in materials will always seek equilibrium with the surrounding humidity. For example, if an environment was to become more humid – say, up to 70 percent relative humidity – materials within that environment would actually absorb moisture until they were holding approximately 70 percent of their capacity. Therefore, the humidity in a room or area must be lowered in order to dry out the materials within it – building materials, carpets, furniture – and to prevent other materials from becoming wet.

Decreasing humidity in an environment will create an “absence” of moisture in the air, which will in turn promote evaporation. Humidity can be decreased by either natural or mechanical means, depending upon the situation. For example, if humidity is consistently lower outdoors than it is indoors, opening windows to create an “open” drying system may help. But mechanical means are frequently needed, and the right dehumidifier (or dehumidifiers) will help lower humidity quickly – and remove moisture from the air as it is evaporating.

Using air movers to direct airflow across a wet surface will help create evaporation. Airflow keeps moisture moving to the surface of materials (carpets, walls, etc.) and pulls that moisture into the air, where dehumidifiers can remove it.

In fact, air movement actually speeds up the process. It ensures that the warm, dry air created by other drying equipment (e.g., dehumidifiers) is quickly and continuously placed into contact with wet materials.

More often than not, a water intrusion or moisture challenge isn’t confined to one small area or corner of a room. When multiple adjacent areas or large areas are involved, airflow is especially critical because it creates air exchange among the affected areas. Without airflow, the humidity and temperature would greatly vary from one area to the next – and drying equipment would need to be installed in every affected air space. Clearly, this is highly impractical.

Airflow can be created easily by using air movers. A broad range of air movers have been designed specifically for promoting circulation and airflow across wet materials. The most common is referred to by drying professionals as snail-shell carpet dryers, and they can help tackle many drying challenges.

Other types of air movers are also available, including specialized dryers that offer face-down or angled positions for spot drying carpets or walls, and high-pressure blowers designed for drying under hardwood floors. Each air mover has its own unique set of features and benefits that can be targeted to provide a solution for each challenge.

One of the most overlooked factors indrying is temperature. But it’s a scientific fact: heat increases drying efficiency. Heat adds energy to water molecules, making them move faster and change in state from liquid to vapor – i.e., evaporation. It’s also true that warm air can suspend more moisture – it is more “thirsty.”

Heat has a significant influence when dealing with hard-to-reach, “bound” water that can exist deep within affected materials. In cold weather, well-placed heat can warm these materials and help avoid condensation.

When water intrusion has led to the growth of severe mold, work often requires shutting down the HVAC system in order to avoid spreading contaminants. In cold conditions, a lack of heat can make it extremely difficult to dry water-damaged materials (not to mention how a lack of heat can make occupants or technicians uncomfortable). In the same way, overly high temperatures can jeopardize some materials and cause building occupants to turn off heat-producing air movers and dehumidifiers, dramatically reducing drying progress.

Adding heat can greatly boost your drying system in several ways, with various types of jobs. However, too much heat or the wrong kind of heat can work against you. The key is to control the temperature and the drying environment to optimize efficiency. Heat can be added with a variety of equipment, including mobile furnaces or portable environmental control units. A unit that provides both heating and cooling options can provide the best flexibility to control temperatures in the drying environment.

The HAT system for drying is fairly straightforward: control humidity and add airflow and temperature to get the highest rate of evaporation and the most thorough drying success. But some water intrusions are less straightforward than others. Complicated moisture related challenges, as well as flooding from