A commonly followed practice within the industry is documenting Humidity Ratio (Grain Per Pound (GPP.) When the Restorer documentation shows the belief that the indication of a well-executed drying strategy is the gradual reduction in humidity ratio (GPP) observed within a given drying chamber. However, it is pertinent to question the integrity of this statement. Could there be instances where this may not hold true? And how would one evaluate such a scenario?
Environment
Day-1: 70°F/68% RH (GPP = 77.4) (Initial Site Arrival);
Day-2: 80°F/55% RH (GPP = 64.7) (What Phase/Stage); and
Day-3: 86°F/46% RH (GPP = 69.7) (What Phase/Stage).
We often try to demonstrate to multiple interested parties (MIPs) that our project is reducing its moisture impact. Grain counting indicates a well-established and effective drying strategy, as the numbers show an increase in air temperature from the initial start. However, one of the challenges we face in the industry is that we record numbers and present them without fully understanding their meaning as the author (“subject manager expert”). If we capture this information and cannot explain it, how do we get paid? If we used these numbers to build and apply to a drying process, we would simply be drying the air, which is not always enough to achieve our desired outcome for the project.
The project asks us an important question: What are you and the equipment here to do? Are you here to reduce the environmental moisture in the air or the moisture in the affected materials?
Ken Larsen wrote Leadership in Restoration in the book, which gives value to explaining that “the vapor pressure is only one-half of the drying methodology for the evaporation rate.” Let’s now explore a potential mitigation scenario. The exterior weather is cold and involves a standard crawl space with primary flooring made of 5/8″ plywood, which needs to be dried. Given the current weather conditions and the situation, do you think it would be advisable to modify the drying methodology?
Plywood Flooring Materials
Day-1: 51°F />30% MC (Initial Site Arrival)
Day-2: 46°F/>30% MC (What Phase/Stage)
Day-3: 42°F/>30% MC (What Phase/Stage)
The material has not dried at all, which is somewhat disheartening. So, now the project and the MIPs’ are starting to ask questions. The restorer responsible for counting the grains would likely be perplexed, as the conditions appeared to be quite favorable with warm air, lowered relative humidity, and decreased humidity ratio. Thus, one may wonder what the issue could be.
Have you managed to identify the root cause?
To solve this issue, it is crucial to determine the dew point temperature of the drying chamber’s surroundings. In this case, the plywood’s surface was cold enough to cause water to condense from the air, making it more humid despite the air becoming drier. Ignoring this situation could prolong the restoration process until the crawl space naturally warms up in the spring, raising the temperature of the plywood. Simply counting grains cannot assess our expertise and could result in ineffective drying techniques.
Grain counting is a valuable technique for determining the amount of moisture in an environment only. This technique is commonly used to calculate the moisture removal rate of dehumidification systems. By quantifying the vapor being processed through the system, it is possible to determine if there is a difference in humidity ratio (GPP) between the air stream entering and leaving the system. This difference is called “grain depression” and is a reliable metric for evaluating the system’s performance.
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