Technical Papers

What is Psychrometry and how does it relate to structural drying?

Thursday, June 4th, 2015 by Bruce Carney

We are the experts in Psychrometry!

Psychrometry is the science and study of the relationship between temperature, relative humidity, grains per pound, vapor pressure, and dewpoint in the atmosphere. Another way of thinking about Psychrometry is that it is like indoor climatology.

Knowing how these physical properties work together indoors on various structural components will determine the procedures used for drying them.  

Two tools that are useful in the application of psychrometry are the Thermo hygrometer and the Psychrometric chart.  With these tools we can monitor our progress in drying out a structure.  Normal relative humidity in a room would be between 30% and 50%, anything above 60% increases the likelihood that mold will grow.

What is Psychrometry and how does it relate to structural drying - Image 1

After we have extracted the majority of the free standing water air movers are used to encourage evaporation of the remaining moisture which when airborne is also know as humidity or indoor clouds. The placement of the high velocity air movers is essential to this process as are the use of dehumidifiers. To remove humidity from the air we use two distinct dehudifiers:  Refrigerant Dehumidifiers and Desiccant Dehumidifiers.  Refrigerant Dehumidifiers are designed with cooling coils to trap the moisture in the air and generally work best in hot and wet environments.  The Desiccant Dehumidifier uses silica gel to capture moisture in the air, and works best in cool and dry environments.The air movers and dehumidifiers compliment each other in this process.

Moderating heat with air flow is an added means of drying. As the heat increases it increases the evaporation rate and, given sufficient dehumidification is in place, it will accelerate the drying process. Having a balance between heat, air flow and the right dehumidification capability is the key to quick and efficient drying with the added assurance that if done within 24-48 hours you will have minimized the likelihood of unhealthy biological growth.


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