Psychrometrics & Structural Drying Principles Flashcards

What are the three recognized phases of structural drying listed in the correct sequence?

Answer: Extraction, Evaporation, Dehumidification

The three phases are extraction (remove bulk water), evaporation (convert liquid to vapor at surfaces), and dehumidification (remove vapor from the air).

Which class of water damage is characterized by a slow evaporation rate and minimal moisture absorbed into materials?

Answer: Class 1

Class 1 water damage involves the least water absorbed by materials, a slow evaporation rate, and typically affects only part of a room.

What temperature range is generally recommended to optimize evaporation during a structural drying project?

Answer: 70°F to 90°F

Warmer temperatures in the 70–90°F range increase vapor pressure in wet materials, significantly accelerating the evaporation rate.

What is the primary function of an air mover in a structural drying setup?

Answer: To increase the evaporation rate by replacing the saturated boundary layer of air at material surfaces

Air movers create turbulence over wet surfaces, replacing the saturated boundary layer of air with drier air, which dramatically accelerates evaporation.

What is 'vapor pressure' in the context of structural drying?

Answer: The partial pressure exerted by water vapor within a mixture of gases

Vapor pressure is the pressure exerted by water vapor molecules; moisture migrates from areas of high vapor pressure (wet materials) toward areas of low vapor pressure (dry air).

What is 'equilibrium moisture content' (EMC)?

Answer: The moisture content a hygroscopic material reaches when balanced with the surrounding air's temperature and humidity

EMC is the stable moisture content a material reaches when it neither gains nor loses moisture to the surrounding air at a given temperature and relative humidity.

What relative humidity level is the accepted target for a restored indoor environment after water damage?

Answer: Between 30% and 50% RH

A relative humidity of 30–50% is the accepted restoration target, preventing both mold growth (above 60%) and over-drying damage to materials.