Condensation becomes possible when moisture-bearing air reaches a surface at or below that air's dew-point temperature. Finding water is therefore the start of a pathway investigation, not proof that cooling equipment is the sole cause.
Literature summaryGCT field methodLimits statedPrimary sources
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Prepared and reviewed by Gulf Coast Technologies, LLC for ICY AC. No professional credential is implied by publication.
Literature summary: dew point is the temperature at which the existing water-vapor content would reach saturation during cooling at approximately constant pressure. Relative humidity changes with air temperature even when the amount of water vapor is unchanged, so dew point is often the clearer indicator of moisture available to condense.
Condensation requires both a moisture source or pathway and a sufficiently cold surface. Supply diffusers, chilled piping, cold ducts, glass and interior finishes can cross the dew point when humid outdoor air, ventilation air, infiltration or indoor moisture reaches them.
Moisture also moves as bulk water, vapor diffusion and air transport. A wet surface can result from plumbing, roof or envelope leakage, drain or condensate failure, capillary movement or condensation; visual similarity does not establish the source.
Surface temperature, air temperature and moisture must be measured at the same location and time. Conditions can differ across a room, inside an assembly and during occupied versus unoccupied schedules, so a single central sensor can miss the critical interface.
Field method
How to test the working explanation.
Record time, location, weather, occupancy and equipment state with every reading. Repeat the same method after a controlled change.
01
GCT field method 1 — Locate and time the moisture: record the exact surface or assembly, first observed time, duration, weather, occupancy and equipment state.
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GCT field method 2 — Measure coincident air conditions: record dry-bulb temperature and relative humidity, then obtain dew point with a documented method; identify the hygrometer, calibration status, stabilization time and position.
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GCT field method 3 — Measure the surface in °C (°F optional), recording material, finish, infrared emissivity setting or contact method. Treat reflective and low-emissivity surfaces with extra caution.
04
GCT field method 4 — Trace accessible drainage, insulation continuity, visible bulk-water paths and pressure-driven air pathways without opening hazardous assemblies. Separate observations from hypotheses requiring destructive or specialist investigation.
05
GCT field method 5 — Trend indoor and outdoor temperature, relative humidity or dew point, surface temperature and system state through the event and after any authorized correction. Preserve raw readings, gaps, sensor movement and uncertainty.
Interpretation boundary
What these observations do not prove alone.
A useful measurement narrows the possibilities. It does not automatically establish root cause, contractual responsibility, code compliance or the condition of inaccessible equipment.
Stop around energized wet equipment, suspected contaminated materials, damaged ceilings, confined spaces or structural hazards. Sampling, remediation, medical interpretation and invasive envelope work require the appropriate qualified professionals.
