According to the IICRC WRT body of knowledge, theinitial dehumidification capacity recommendationis determined by three primary factors:cubic footage of the affected area,class of water intrusion, andtype of dehumidifierbeing used. This calculation establishes a baseline moisture removal capability required to manage the anticipated evaporation load.
Cubic footage defines the volume of air within the drying chamber and directly influences how much moisture must be removed from the environment. Theclass of waterdescribes how much moisture has been absorbed by materials and the rate of evaporation expected. Higher classes (Class 3 and 4) require substantially more dehumidification capacity due to increased moisture loading and deeply absorbed water.
Thetype of dehumidifieris equally critical because different technologies (conventional refrigerant, LGR, desiccant) have vastly different operating ranges, efficiencies, and moisture removal characteristics. The WRT manual specifically differentiates capacity calculations for LGR versus desiccant systems, as they function under different psychrometric conditions.
Factors such as category of water, subfloor type, or air mover quantity influenceprocedural decisions, safety, and drying strategy—but they are not part of the initial capacity calculation. Likewise, grain depression is a performance outcome used for evaluation, not an input variable.
This structured approach ensures consistency, defensibility, and alignment with the ANSI/IICRC S500 Standard, enabling restorers to justify equipment placement using measurable, science-based criteria rather than guesswork or habit.
