Question: Our company recently made a change in the workflow that calls for a temperature reading at each moisture reading point. The reasoning is that there have been changes in the IICRC S500 that call for this. I have not heard of this, have you? I don’t understand why a temperature reading would need to be taken and recorded here, as the temperature and RH should have already been recorded. Any ideas on this?
Answer by Jeff Bishop, SCRT Technical Director :
By temperature reading, are you (they) referring to the atmospheric or material temperature?
If atmospheric, I would agree that this has always been standard practice (and required by S500), since it’s not possible to get to the humidity ratio (HR in gpp; formerly expressed as specific humidity or SH) without both temperature and humidity readings.
The temperature of materials impacts the absorbed moisture’s vapor pressure. As you know, moisture always moves from high vapor pressure to low vapor pressure (i.e., wet always goes to dry if it can). Therefore, if we heat a material (and its absorbed moisture), the absorbed moisture’s VP increases. Once the absorbed moisture’s VP is increased higher than the VP of moisture in the surrounding air, then evaporation is enhanced.
If they are suggesting that the temperature of a material be recorded, then it’s also essential to measure the temperature and RH in the surrounding air. That way, we can calculate the VP of both the absorbed moisture and the VP of the air. Of course, the higher VP of absorbed moisture and the lower the VP of the surrounding air, the higher the evaporation potential.
Obviously also, the dew point temperature on materials as well as the atmosphere is to be avoided as well.
Hope this helps; write if questions remain.
Follow up Question: Thanks for the response. I can see where this is going if it actually becomes part of the Standard. Opening some doors for the proponents of heat drying.
Of course you are right. Although heat or temperature control always has been a component of the principles of drying (i.e., remove excess, promote evaporation, dehumidify or ventilate, control temperature) for over 35 years in the IICRC S500 (1st edition in 1974), it seems that it’s been newly discovered by some who weren’t even born at that time. And it’s not just heating the entire structure; the emphasis today is on direct heat application in order to avoid corollary damage to unaffected (dry) components not involved in moisture absorption.
It’s also interesting to note that, in the early 70s, I was using livestock dryers (hair dryer on steroids) to blow hot air between double-jute-backed carpet and natural fiber (jute) pad – the first use of in-place drying. “Don’t worry ma’am, the musty odor will disappear in a week or so.”
Yipes! We didn’t know why, but we were getting things dry in two to three days, even without dehumidifiers. We might even have been killing or at least controlling microbial growth as well with 120-130°F under the carpet.
In annotating the Water Restoration Technician (WRT) exam for my course of instruction, I noticed more emphasis on heat as a drying tool.Primary tools for heat drying involve containing affected materials, followed by installing directed-heat units, ducted dehumidifiers (particularly desiccants, which combine heat with low-humidity air), or IR lamps for spot drying of wood, concrete, ceramic tile and other materials that aren’t particularly heat sensitive. “