A drying environment is defined as one in which general environmental conditions are such that evaporation from damp or wet materials is encouraged, leading to rapid reduction in moisture content. A drying environment can be created and maintained in an entire structure, a portion of a structure that is isolated from the rest of the building, or even in an interstitial cavity.
The purpose of a drying environment is to dry materials quickly and efficiently to a predetermined drying goal. Controlling conditions and characteristics of the air in the environment is the primary way to accomplish this goal. Evaporation from materials is accomplished by managing airflow, temperature and humidity:
- Moving air rapidly across surfaces of wet materials is especially effective during the initial stages of drying, when evaporation is primarily from surface and free water, but less effective once surface moisture has evaporated.
- Increasing the temperature of the air provides the energy necessary for rapid evaporation and also, it inherently decreases relative humidity, providing more capacity for the air to hold moisture.
- Reducing humidity further enhances the moisture holding capacity of air. Humidity reduction and control are especially critical in the latter stages of a project when most surface and free water has evaporated and remaining moisture is more difficult to remove.
These three factors (airflow, temperature, humidity) interact with each other, and with other factors, in complex ways that determine the rate of evaporation. Different factors may be more important in different stages of the drying process, requiring modifications in procedures to promote maximum drying efficiency.