Being aware of the ambient air temperature of the room you’re trying to dehumidify is another tool in your toolbox of combating any humidity problem. The relationship between temperature and humidity is more complicated than you might expect. Instead of showing you charts and graphs and having an extensive discussion explaining this relationship we’ll simply highlight its end result – the lower the air temperature, the less amount of moisture needs to be in the air for the same humidity reading. You might have heard before that “the lower the temperature, the less moisture the air can hold”. While this isn’t technically true (air can’t actually “hold” moisture) what it implies is correct. You see this phenomenon in action every day when you take a shower. You’ve probably noticed that the warm moist air created by your shower condenses onto cold surfaces in your bathroom such as your bathroom mirror. The cold air surrounding the cold surface can’t “hold” nearly as much moisture as the warm moist air surrounding it. What it cannot “hold” condenses as liquid water on the mirror.
Relative to the current discussion, the important point here is that a block of air at 50% relative humidity and 50° F “holds” much less moisture than that same size block of air at 50% relative humidity and 90° F. To further explain this phenomenon let’s imagine two different scenarios. In one scenario you have a moisture problem in which the ambient air is at 80% RH and the ambient air temperature is 90° F. You turn your dehumidifier on and set it to a desired humidity level of 40% RH which it reaches after a few hours of operation. In another scenario the initial ambient air temperature is 50° F. The starting RH is again 80% and again you set your dehumidifier to a desired humidity level of 40% RH. Again it achieves this desired humidity level in a few hours. Which scenario results in more moisture removal?
The answer here is that much more moisture is going to be removed in the first scenario because the warm air at 80% RH “holds” much more moisture (that can be removed) than the colder air at 80% RH. Thus, you can expect the dehumidifier’s condensate collection bucket to fill up with much more moisture in going from one extreme humidity level to another at higher temperatures than you can at lower temperatures.