Letter to the Editor: The Industry Misunderstands Grain Depression

Publisher’s Note: We welcome dialogue and feedback on what you read in C&R! In the May/June issue of C&R, we published an article on grain depression – which drew a lot of support – and some counter discussions. Below is a “Letter to the Editor” response from two restoration instructors.

Have feedback of your own? Reach out to me directly at michelle@candrmagazine.com.

The restoration industry has an incorrect understanding when it comes to grain depression on dehumidifiers, and it’s time to set the record straight. 

To begin, unless there are strict and scientific conditions set to be reached within the drying chamber, there is no need to evaluate the performance of equipment like dehumidifiers or heaters. Before E3 (Enthalpy, Evaporation, Evaluation), there were none.

Our industry has taught us how to take the moisture content of materials at any given point on a water loss, that’s about it. 

This is a wakeup call to our industry! 

Think about what you are doing and why are you doing it. Then give evidence to back up your actions. 

Most restorers in our industry cannot do that. 

The industry has produced the IICRC S500 Standard of Care 5th Edition which leaves room for ambiguity to which all materially-interested parties need answers. Before E3, there have been no indisputable drying metrics available, leaving the restorer to consistently defend or be susceptible to the drying strategy being discredited.

As restorers, we are often evaluated on a metric such as grain depression which is not defined in our standards.

Chamber Conditions

The first metric to evaluate is the chamber conditions and where it should be on any given day, with any class of loss, during any outside conditions, and when using any drying equipment before you can establish the performance of the equipment. Unless we evaluate the evaporation ability of the air, there is no reason to evaluate the performance of the equipment used to achieve these conditions. Most of the industry is satisfied with demonstrating that there is some level of grain depression with the equipment versus knowing exactly what the grain depression should be. This is where our industry gets it wrong. 

With E3, in any condition, it will tell you how any piece of equipment should be performing based on the minimal performance of that type of equipment. The idea of “at least a 5-grain depression” or being satisfied with demonstrating some level of grain depression can be put to rest.

It is an unscientific evaluation and guessing is not acceptable!  

The grain depression of any DH might be 40 and sometimes it might be 2, and this can all be proven based on how a dehumidifier works scientifically. The math cannot be argued.  

It is very important to be able to evaluate the performance of any piece of equipment, but this is secondary to evaluating the chamber conditions.

The conditions achieved within the chamber are what directly affect the rate at which the materials return to equilibrium moisture content values.  

Once again, this has never been defined in our industry!  

All we know how to do is assess the actual moisture content and then look at the performance of the equipment and be satisfied with some level of grain depression or apparently in some instances, a minimum 5 grain depression. This behavior is exactly why the insurance industry pushes back on so many drying invoices!

To say that the performance of the equipment is not important to the conditions of the chamber is as wild as saying that the heat and airflow coming off a clothes dryer has nothing to do with the drying performance of the clothes. They go hand in hand and they both can and need to be defined. Until now, restorers are left wide open for ambiguous arguments that are based on either nothing or bad science. 

As a professional restorer, where should the chamber be in terms of conditions at any point within a job?

E3 is an evaluation of any given condition and its evaporation ability; E3 Targets are an evaluation of what any chamber should at least be based on all variables at any given point on the loss!

Once that is established, it is crucial to understand what is needed to achieve these conditions and the scientifically proven algorithms that dictate the performance of the equipment being used.  

It’s Not Arbitrary; It’s Math

The sensible and latent energy content of any DH or heater can be exactly defined within any condition to make sure it is working like it should be. If a dehumidifier (or however many on a job site) should have a grain depression of 35 and it is only 12, then the chamber conditions will not be achieved.

At the same time, if the conditions within the chamber dictate (based on the same math) that the DH’s should have a grain depression of 2, then that is what it should be. Sometimes the expected grain depression should be 0 and that should be based on the same math, and that cannot be disputed.  

It is very simple. If the conditions in the chamber are 85F/62%RH/115GPP, then the minimum grain depression of an LGR should be 29 in the case of a dehumidifier with by-pass, and 42 grain depression on a dehumidifier without by-pass. Those same conditions with a conventional dehumidifier, or HVAC unit should produce a grain depression of 26. In these conditions, if your dehumidifier is only producing an “acceptable” 5-6 grain depression, your dehumidifier is not functioning properly.

If the conditions in the chamber are 76F/27%RH/37GPP, then the grain depression should be 3 on a DH with by-pass, and 5 on a DH without by-pass. In these conditions, your dehumidifiers are below the ambiguous 5-6 grain depression, but are still functioning properly.  Just as simple, if the conditions being brought into the return of a desiccant are 82F/52%RH/87GPP, and the reactivation inlet of the desiccant coming from outside is 67F/55%RH/55GPP, then the minimum grain depression of the desiccant functioning properly should be 29 or higher. 

This is how equipment should be evaluated. It is not arbitrary; it is all math.

The performance of the equipment and the daily chamber conditions go hand in hand and they both directly affect the rate at which the moisture content of the materials is returned to equilibrium levels.

They both must be defined by math and until this happens, it is a waste of time to discuss grain depression of equipment.  To say grain depression is not important only works if you do not define what the chamber should be throughout the loss, and currently this is what our industry does.  Now that we can define what the chamber should be (with all variables factored in) it no longer holds any water.  

The performance of the equipment dictates the chamber conditions which also dictates the rate at which materials are returned to equilibrium. To say that the performance of the equipment is not important is absurd unless you don’t care how quickly the materials will be brought back to equilibrium.  

Stop Drying Backward

Grain depression has not been important to us because the chamber has not been important or defined by our industry. The chamber can now be defined, and so can the grain depression. One affects the other, and now we can get away from the ambiguous minimum of 5-6 grain depression in all conditions and quit saying that grain depression does not affect the materials. 

It is time to stop drying these buildings backwards as an industry, but more importantly it is time for the restoration industry to define to the insurance companies and consultants how these jobs should be dried, and not the other way around. This can now be done with E3 and before that it was not possible because everyone’s opinion could be enforced. Not anymore. 

When you think about it, this is where our industry is currently at!  It is time to remove the ambiguity within our industry and bring consistent, repeatable, scientific, and mathematical metrics to define our drying projects.  E3 does this for us and now is the time to integrate E3 into field management software systems to help all parties be on the same page before, during and after the project.   If you do your job correctly as a restorer, you should be paid in full, and if you didn’t then the bill should be negotiated, but both should be based on the same science and math!   

Chuck Dewald III and Chris Laney
Dewald Academy of Drying


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