Structural Drying and Moisture Control

Drying

The process of drying is managed through air movement, humidity level, and temperature. Fans, blowers, and carpet dryers are used to create air movement that increases the rate of evaporation of water from wet materials. It will be necessary to move chair pads and furnishings to allow air movement to reach all areas. In some cases it may be necessary to open venting holes in walls and cabinets to facilitate air movement. The relative humidity level is the primary factor in determining drying effectiveness. For small floods, the building's ventilation system may have adequate capacity to maintain optimal relative humidity levels. For larger floods, it will be necessary to bring in industrial dehumidification or desiccation equipment to manage humidity levels in the building. Temperature will help indicate which type is appropriate. Below 68° F refrigerant dehumidifiers can ice up and desiccant dehumidifiers may be a better choice. Home dehumidifiers are not up to the task. For optimal drying the relative humidity should be maintained below 40%.

Temperature influences evaporation rate, relative humidity, microbial growth rates, and occupant comfort. Higher temperatures increase the amount of water the air can hold, and speeds up evaporation. Higher temperatures also speed up the growth rate of bacteria and molds, increasing concerns of adverse health effects and odors. Cooler temperatures reduce the microbial growth rate, but can also cause condensation of moisture in the air. With very low temperatures occupant comfort becomes a concern.

Opening windows is not a good way to speed drying. Mechanically ventilated buildings rely on building pressurization to regulate the flow of air through the building. Opening windows will change the balance of the building pressurization, and upset the airflow. In the warm months an open window can allow humid air into the building. In cold months, the open window can rapidly cool the building resulting in condensation of water onto building surfaces. Open windows also present security concerns.

Structural Drying Calculations

CUBIC VOLUME OF AIR= Length x Width x Height {in feet)

ONE AIR CHANGE PER MINUTE= Cubic Volume of Air/ 60 = CFM (cubic feet per minute)

REQUIRED AIR CHANGES {Desiccant)=to 4 Varies with moisture  load and density

AIR MOVER SIZING= 1per 15 to 25 linear feet of wall. Varies with moisture load and density

DRYING TIMELINE = 3 to 21 days. Varies with moisture load and density