Airflow – Use in Building Drying
Air movement has shown to be very important for rapid building drying. It serves to remove saturated air from near the surface of materials, deliver dry air to all affected areas, and to stimulate more rapid evaporation of moisture from damp surfaces.
Airmovers are usually most beneficial at the beginning of a drying program, when the fastest evaporation is occurring. Materials that absorb water particularly quickly, such as carpet, underlay and plasterboard, also give up that moisture quickly particularly if high velocity airflow can be achieved.
“In many structural drying situations, one of the most difficult areas to dry is the lower part of the wall where it meets the floor”
As to how many airmovers should be used in a drying job, there is some guidance from IICRC (Institute of Inspection Cleaning and Restoration Certifications), which is that airmovers ‘…should be set up so that continuous rapid airflow is provided across wet surfaces. In many structural drying situations, one of the most difficult areas to dry is the lower part of the wall where it meets the floor. Restorers should install one airmover for each 3 to 5 linear meters of wall, with the outlet of each airmover pointing in the same direction…’
After the first 48 hours it would be expected that all surface water would be gone (assuming adequate extraction too place before drying equipment was installed). After this period, evaporation rate should fall and less airflow would be required.
A variety of studies has shown that during the initial period of drying, when a high velocity is required, airflow rates of around 3 – 3.5 meters per second should be achieved. After this initial period, as evaporation rates fall, a reduced rate of 0.5 – 1.5 meters per second is applicable. These figures can be measured with an anemometer.
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