Applied Structural Drying key terms

The study of the physical properties of moist air and how temperature, pressure, and water vapor content interact during drying. It underpins decisions about airflow, heat, and dehumidification capacity.

The ordinary air temperature measured by a thermometer exposed to the air but shielded from radiation and moisture. It is one of two temperatures needed to plot a psychrometric state point.

The lowest temperature air can reach when water evaporates into it without added heat, reflecting evaporative cooling. The gap between wet and dry bulb indicates how much drying potential the air still has.

The difference between dry bulb and wet bulb temperature. A large depression means dry air with strong evaporative capacity; a small depression means humid air that is near saturation.

The percentage of water vapor in air compared with the maximum the air could hold at that temperature. It changes with temperature even when the actual moisture content stays constant.

The mass of water vapor carried per unit mass of dry air, often expressed in grains per pound. Unlike relative humidity, it does not change when air is heated or cooled.

The mass of water vapor divided by the total mass of the moist air mixture. It is closely related to humidity ratio but uses total air mass in the denominator.

The temperature to which air must be cooled for water vapor to begin condensing at constant pressure. Air at or below its dew point produces condensation on surfaces.

A graph plotting dry bulb temperature, humidity ratio, relative humidity, dew point, and enthalpy so a single air state can be read and drying processes traced.

The total heat content of moist air per unit mass of dry air, combining sensible heat and latent heat of the vapor. It is used to size heaters and compare air states.

Energy absorbed or released when water changes phase without a temperature change, such as evaporation or condensation. It is the dominant energy cost in structural drying.

Heat that changes the temperature of a material or air without changing its phase. It is measured by a thermometer and drives the temperature rise across heaters.

The moisture level a material settles at when exposed to air of a given temperature and relative humidity. Drying is considered complete when the material reaches this level.

The change of liquid water into vapor at the wetted surface, driven by a vapor pressure difference between the surface and the surrounding air.

The partial pressure exerted by water vapor in air. Drying occurs when vapor pressure at the wet surface exceeds vapor pressure in the surrounding air.

The change of water vapor into liquid when air is cooled below its dew point or contacts a colder surface. It can re-wet materials and is a common drying failure.

The amount of water in a material, usually expressed as a percentage of its dry weight. It is the primary measure used to judge drying progress.

An instrument that estimates moisture in materials, typically using electrical resistance or capacitance. Pin meters give localized readings; pinless meters scan larger areas.

An infrared camera technique that shows surface temperature differences caused by evaporative cooling or retained moisture. It guides inspection but must be confirmed with a moisture meter.

A scaled sketch or diagram of an affected area marking wet, dry, and affected zones along with readings. It documents the drying boundary and supports planning and reporting.

A method using a moisture meter in a known dry reference area and the suspect area to distinguish surface moisture from moisture within the assembly.

A recorded set of air conditions, typically dry bulb, wet bulb or relative humidity, and dew point, taken in affected and unaffected areas. It establishes the drying goal and verifies performance.

A record of readings, equipment status, and observations taken at set intervals. It proves the drying plan is working and provides evidence for scope and billing decisions.

The target moisture level or psychrometric condition that defines when drying is complete, usually based on dry standard readings from an unaffected area.

A moisture reading taken from a comparable unaffected material in the same building. It serves as the benchmark for judging when affected materials are dry.

A baseline measurement taken before drying begins or in an unaffected area, used to compare later readings and confirm progress.

The removal of water vapor from air to lower its humidity ratio and keep the drying gradient favorable. Common methods are refrigerant and desiccant systems.

A unit that cools air below its dew point so water condenses on a coil, then reheats the air. It works best in warm, humid conditions.

A unit that attracts water vapor onto a desiccant material and regenerates it with heat. It performs well in cool or low-humidity conditions where refrigerant units lose efficiency.

A fan or blower positioned to move air across wet surfaces, speeding evaporation and disrupting boundary layers. Placement matters more than raw airflow volume.

The volume and direction of air movement across and through an affected space. Adequate airflow carries evaporated moisture to the dehumidifier and reduces localized humid pockets.

The number of times the air volume in a space is replaced or circulated each hour. It is used to check whether airflow and dehumidification capacity match the space.

The thin layer of nearly still air clinging to a wet surface. Moving air thins this layer, allowing vapor to escape and accelerating evaporation.

A physical barrier that limits the spread of dust, moisture, and contaminants between affected and unaffected areas. It protects occupants and keeps drying conditions controlled.

A pressure condition in which a contained area is kept slightly lower than surrounding spaces so air flows inward. It prevents contaminants from escaping the work zone.

A device with filters, often HEPA, that circulates and cleans air in a work area. It is used with containment to protect occupants and equipment.

A written description of the drying tasks, equipment, and areas covered by the project. It anchors scheduling, customer expectations, and billing.

A classification of water damage by contamination level, from clean water through grossly contaminated water. It determines protective measures and whether materials can be dried or must be removed.

A classification based on the extent of water absorption and the amount of area affected, which drives equipment sizing and drying strategy.

Gear such as gloves, respirators, eye protection, and protective clothing worn to reduce exposure to contaminants, mold, and chemicals during inspection and drying.

The ongoing process of explaining findings, drying progress, timelines, and limitations to the building owner in plain language, reducing disputes and managing expectations.