By Jeremy Reets
“Nothing in life is to be feared, it is only to be understood. Now is the time to understand more, so that we may fear less.”
I find it interesting that there is a fear of using energy in restorative drying.
There are a multitude of articles that have been written cautioning restorers about the dangers of using energy to dry materials. Ultimately, as Marie Curie stated, it is the lack of understanding that allows room for this fear. It is time that as professionals we replace fear, and the conversations that play on that fear, with knowledge, understanding and insight.
Insight is an interesting concept. It is not simply knowledge. It is greater than understanding. Insight is the understanding of a specific cause and effect in a specific context. It is knowing what to do. There are really three steps to having insight in a specific context, including the use of energy or heat in drying.
The first step is knowledge. It means that we have some degree of education on a subject. Then understanding may come. This means that to some degree we are familiar with the logic of a subject. And then insight follows, meaning we know what to do with the understanding.
For example, knowledge tells us that a train is coming down a track. Understanding means that we realize that the train will hit us if we stay on the track, and insight tells us to get off the track.
It is the lack of insight that leaves us in fear.
Four drying principles
It is widely understood there are four basic principles that drive drying: Rapid air flow, humidity control, adding energy to the water and proper application of these to the water. I summarize this as hot, dry airflow to the water. Since this article is focused on energy, consider just a few basic rhetorical questions regarding air flow and humidity control:
Rapid air flow
Why does rapid air flow assist in the drying process? What affect does it have on the conditions for drying? Why is rapid air flow a necessary element? Why is merely using “sensible” air flow not as effective? How much air flow do you need to properly dry commonly found building materials?
While it would seem that these are questions that we should have answers for as an industry, the debate that rages over the use of air movement as suggested by the IICRC S500 Standard and Reference Guide for Professional Water Damage Restoration proves otherwise.
As you choose water damage education, these are questions to which you should expect a logical and proven answer. Unfortunately, the answers will not be found in most classes. You have the responsibility to search for the answers.
How does drying the air assist in the drying process? How does drying the air move water in the vapor phase? How does drying the air affect evaporation from the surface of wet materials? How low does the humidity ratio need to be to motivate a phase change of water from liquid to gas? What are the primary roles of humidity control in drying?
Again it would seem that we should have the answer to most of these questions readily at hand, but that is not the case. There are many opinions but few actual facts in the water damage restoration community, but they can be found. Without answers to these questions we cannot possibly move beyond knowledge into understanding or insight regarding humidity control and rapid air flow.
There is even less that is understood regarding the use of energy in water restoration than either of the preceding two basic principles we have discussed. It is a complex subject, but let’s just scratch the surface of the use of energy in drying. Consider this fact: You must add energy to the water on every water loss. This is not optional in drying, as energy is required for a phase change.
There are three phases of water that are found on earth. Solid, liquid and gas, also referred to as ice, water and vapor. Each of these phases is determined by the energy level of the individual water molecules. This is why in the winter you could find snow by an unfrozen lake with humidity in the air. All three phases of water can coexist in the same environment.
What determines the phase of the individual molecules is the energy level of each. If you want to turn the snow into water you add energy. Continue to add energy and you will convert the liquid water into vapor. It’s a quite simple and logical sequence of cause and effect. How does this observation affect drying? Again, quite simply, we motivate evaporation by adding energy.
This is how drying works on every water loss on which you work. Consider the last time you used an IR camera to view a water loss. What indicated potential moisture in the materials to you? The camera visually identified cool areas in the affected areas, and this indicated materials to check with your moisture meter. Why is it that we see those cooler areas and suspect potential moisture? Evaporative cooling — a loss of energy at the surface.
Why does evaporative cooling occur? When water evaporates from a surface, it takes some of the energy from that surface to go through the phase change from liquid to vapor. This apparent loss of energy is known as the “latent heat of vaporization.” The energy is not lost but is now at work in the vapor and cannot be measured as temperature. That energy will be released when the vapor condenses back to liquid and can again be sensed by a thermometer as heat, energy available to do work.
Latent heat of vaporization is observed when you are boiling water. At sea level boiling water will remain at 212 degrees Fahrenheit until all of the water in the pot is gone. It will never reach 218 degrees Fahrenheit. If the pot of water is on a heat source, there is certainly energy being added to the water, but it is not observable as temperature increases above 212 degrees Fahrenheit. All of the excess energy is carried away by the vapor leaving the surface.
One way to understand this concept is that each molecule of vapor is like a battery storing energy. How does knowing this lead to a better understanding of drying?
Evaporative cooling naturally slows the drying process as it removes energy critical to continued evaporation from the wet surface. This is observed each time we use an IR camera as a cool surface. If left unchecked, the surface would cool until the vapor pressure of the water at the surface of materials and the air reached equilibrium and evaporation stopped.
If you enter a new water loss that has been sitting for many hours or a few days and the air is very humid, you may notice that your IR camera doesn’t show you any water patterns. The water and air are at or near equilibrium. Turn on an air mover, add energy to the surfaces or open the doors and windows, and you will see the wet areas show up on your IR screen as evaporation starts again.
In order to prevent this equilibrium from occurring, restoration professionals add energy, perhaps not even knowing that they have. Dehumidifiers add energy to the environment. HVAC can add energy to the environment. As the temperature of the environment increases, the amount of energy available to the water increases. Where energy was lost due to evaporative cooling, energy is replaced and evaporation can continue.
The understanding we gain from this knowledge of energy, then, is that in all cases we have added energy to the water where evaporation continued. By replacing this energy lost from wet surfaces during evaporation, we prevent the water and the air-vapor pressures from reaching equilibrium. The result is that porous materials dry. There is nothing to fear besides not adding energy to the water.
Insightful application of energy in drying
Now that we have a bit of understanding of energy in drying, how can we make insightful use of energy in drying? There is a human tendency to believe that, if a little of something is good, a lot must be better. While that is true of evaporation, it is not true of restorative drying. This is why often when the subject of energy in drying is addressed there is an immediate leap to the dangers of heat. These improbable dangers are highlighted instead of the value of proper energy usage.
So what is acceptable energy usage without the dangers so prominently featured? When making application of energy, there is no place for heating the ambient air of the drying environment to 110 degrees Fahrenheit, 115 degrees Fahrenheit, 120 degrees Fahrenheit or more. Ambient temperatures of 85 to 95 degrees Fahrenheit will make significant, yet safe improvements to drying conditions.
In addition to ambient temperature increase, there are ways for you to make direct application of energy to motivate evaporation. Directing heat to targeted areas is the most effective way to utilize energy when drying. To employ this technique, use specifically designed directed-heat drying equipment to blow heated air under containments for wide distribution of the energy to wet surfaces. Or direct the outlet of the unit at a wet surface much like you would use a hair dryer. These units are typically designed to increase surface temperatures 15 to 35 degrees Fahrenheit above ambient temperatures. You may also use the outlet of a dehumidifier in much the same way, but the energy output will be lower.
You can measure the effect of the energy application to the wet surface by calculating the vapor pressure differential of the air and the water. (There are calculators available for this calculation.) As the vapor pressure differential increases, so does the potential for evaporation. The rate of evaporation cannot be determined from this calculation because of additional variables including porosity, moisture content, surface area and availability of surface moisture. We can conclude that regardless of these factors, the potential for evaporation of moisture from those materials has increased.
This is just a very brief address of only a small aspect of energy use in drying. While there is wisdom in being cautious, living in fear doesn’t make sense, and there certainly isn’t any reason to fear the proper use of energy in drying. Additionally make certain that the answers to all of the questions we asked about air flow and humidity control are also at your ready. Seek out opportunities to learn more so that you can make insightful application of energy, air flow and humidity control in drying.
Jeremy Reets operates Sharpsburg, GA-based Reets Drying Academy, www.reetsdryingacademy.com/devs, where he hosts and instructs IICRC WRT, ASD and Restoration Estimating Courses. He produces ReetsTV, a 130-module online water damage restoration training series. Reets is the innovator behind the Reets Evaporation Method, the Evaporation Potential Formula and the TES drying system. He can be reached at Support@ reetsdryingacademy.com/devs.