WestCon Tribune

April 2009

Many construction professionals do not appreciate the ease and potential benefits of using temperature and relative humidity readings to calculate (with readily available psychrometrics software) the ambient moisture content within walls, rooms or buildings. Arguably, most building contractors and field inspectors remain intimidated by psychrometrics, the seemingly arcane realm of specialized engineers who speak knowingly of such esoteric subjects as enthalpy, sensible heat, wet-bulb temperature and sling psychrometers.

Westcon member Lonnie Haughton’s presentation will avoid the complexities of psychrometric science. Instead, the target audience (construction professionals like him with little, if any, engineering expertise) are introduced to only two perhaps-unfamiliar terms, relative humidity and humidity ratio, and then learn that the humidity ratio is simply another term for the moisture content of the air space within the wall or building that is being investigated. He then will show that the humidity ratio is easily calculated (by inexpensive software) if the ambient temperature and relative humidity are known.

Lonnie will present case studies in which portable humidity/temperature loggers were deployed to collect extended series of ambient temperature and relative humidity (RH) readings to assist investigations of problematic moisture within walls and buildings. He will use these case studies to demonstrate that in a manner comparable to using handheld moisture meters for exploratory evaluations of rainwater leakage at building envelopes, no advanced education or engineering expertise is necessary to use extended data series (e.g., RH and temperature readings taken every 5 minutes for 45 days) from the dataloggers to track humidity ratio trends and deviations that help confirm (or rule out) suspected mechanisms, pathways and origins of problematic moisture.

Lonnie will briefly explore the merits of qualitative (or comparative) evaluations of ambient humidity data (as opposed to the various quantitative calculations that might be made by air-conditioning engineers or similar professionals with more-advanced training and skills). The case studies will provide real examples of how humidity dataloggers can be used for highly informative comparisons over time of ambient moisture content levels within a building or its exterior walls.

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