Applied Structural Drying flashcards
Applied Structural Drying · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Specific humidity (humidity ratio)
- The mass of water vapor per mass of dry air, commonly expressed in grains per pound of dry air. It stays constant when air is heated or cooled without condensation.
- Relative humidity
- The ratio of actual water vapor pressure to saturation vapor pressure at the same dry-bulb temperature. Heating air lowers RH even when the moisture content is unchanged.
- Dew point
- The temperature at which air reaches saturation when cooled at constant pressure and humidity ratio. Surfaces below dew point collect condensation.
- Vapor pressure deficit
- Saturation vapor pressure minus actual vapor pressure at the current conditions. A larger deficit means stronger driving force for evaporation from wet materials.
- Equilibrium moisture content
- The moisture content a material reaches when its vapor pressure matches the surrounding air. Drying stops when material EMC equals ambient conditions.
- Evaporative cooling
- The temperature drop caused by water evaporating from a wet surface. A wet-bulb reading below dry bulb indicates active evaporation.
- Pin-type moisture meter
- An instrument that measures electrical resistance between two probes driven into a material. Resistance falls as moisture rises, so readings are relative and material-specific.
- Pinless moisture meter
- A capacitance or impedance meter that scans a field without penetrating the surface. Best for mapping moisture patterns, not for absolute moisture content values.
- Thermal imaging
- An infrared scan showing surface temperature differences. Wet areas often appear cooler from evaporative cooling, but findings must be confirmed with a moisture meter.
- Dry standard
- A reference moisture reading taken from an unaffected area of the same material and orientation. Material readings are compared to it to judge drying progress.
- Deep-wall probe
- A long probe used to test moisture inside wall cavities without full demolition. Often paired with baseboard removal to test the bottom plate.
- Moisture map
- A labeled diagram showing numbered test locations and readings. It lets each day's readings be compared to the same spots for reliable progress tracking.
- Drying log
- A daily record of date, time, temperature, RH, GPP, material moisture readings, and equipment status. It documents progress and supports billing and dispute resolution.
- Documentation of equilibrium
- Showing material readings returned to within tolerance of the dry standard and stayed stable across consecutive readings. This demonstrates the drying goal was met.
- GPP trend
- Grains per pound of moisture in the air, tracked over time. A falling GPP with rising material dryness indicates the drying system is working.
- Equipment runtime record
- Logged hours of operation and downtime for dehumidifiers and air movers. Performance depends on continuous operation and defrost cycles.
- Three drying functions
- Extract standing water, evaporate water from materials with airflow and heat, and remove vapor from the air with dehumidification. All three are required.
- Containment
- Poly barriers, zippers, and sealed doorways that isolate the drying chamber. It reduces the volume the dehumidifier must treat and controls moisture migration.
- Dehumidifier sizing
- Estimating gallons of water to remove and required pints per day, then selecting equipment with margin. Undersizing lets humidity rise and drying stall.
- Open versus closed drying
- Open drying exchanges outdoor air when outside vapor pressure is lower. Closed drying uses dehumidification when outside air is humid.
- Air mover placement
- Positioning air movers to sweep wet surfaces at an angle, creating turbulent high-velocity airflow. Avoid directing air into corners where it stalls.
- Refrigerant dehumidifier
- A unit that condenses water on cold coils. Most efficient at higher humidity and warmer temperatures; capacity is rated at specific conditions.
- Desiccant dehumidifier
- A unit using a rotating desiccant wheel to absorb moisture. Works well at low temperatures and low humidity where refrigerant units lose efficiency.
- LGR dehumidifier
- A low grain refrigerant unit designed to keep extracting water at lower humidity ratios than standard refrigerant dehumidifiers.
- Negative air machine
- Equipment that exhausts air from containment to maintain a pressure differential. It controls migration of dust, spores, and odors.
- HEPA filtration
- High-efficiency particulate air filtration used when the scope includes microbial contamination or when containment requires particle control.
- Defrost cycle impact
- Low-temperature operation triggers defrost cycles that reduce effective daily water removal. Monitor actual water removed rather than nameplate ratings.
- Scope of drying
- The defined boundary between materials that can be dried to standard and those removed, such as saturated padding or contaminated materials.
- Drying plateau
- A point where material readings stop falling. Low GPP means the goal is met; high GPP means the system is failing.
- Change order
- A written adjustment to scope and cost when hidden moisture, new affected areas, or extended drying times appear after the initial estimate.
- Asbestos and lead assumption
- Assuming older buildings contain asbestos or lead until tested. Suspect materials are not disturbed without assessment.
- Occupant communication
- Explaining equipment noise, power use, expected duration, and areas to avoid. Advising at-risk occupants about mold exposure and physician consultation.