How temperature and humidity relate

Arctic Bowl

Arctic Bowl

Well-Known Member
We're doing a post for everyone to help understand just how temperature and humidity work together and what we can expect to happen from any changes we make in our grow rooms. We're going to start with a single molecule, a single molecule that we are going to say is at 70 deg F, this single molecule at 70 F we are going to say is at 50% RH. This single molecule that we are saying is at 70F and 50% RH can be pictured like this.

image18940.jpeg


Now we know that as temperatures rise and drop most things expand and contract. Molecules follow this and as temperatures rise they expand and as temperatures fall they contract. So, let's say that we take this same single molecule that we pictured above and do nothing more to it than raise its temperature 5 degrees F. What happends? Well, the single molecule expands because of the rise in temperature. That expansion of that single molecule also caused something else to happen during its expansion. It caused the RH of that single molecule to decrease from its original 50% RH to a lower RH, the RH in our single molecule is now closer to 42% RH. Now let's say we take our single molecule that is now at 75F and 42% RH and we lower its temperature to let's say 65 F, we did nothing more than drop its temperature, we didn't add anything else just subtracted temperature. What happends? Well, our single molecule contracted and during this contraction the RH has now increased from the 42%RH it had at 75 F to closer to 58%RH.

How do we know this is what our single molecules RH will be at 75F and 65F? By using the Psychrometric chart. The Psychrometric chart will give us more information than most of us will ever use in or grow rooms but it is a handy chart to use to see where we are it as far as our environment in the grow room is concerned.
 
So, what can we do with this information and how can it help us in our grow rooms? Well let's take a few readings from our grow room, let's get our temperature reading from our grow room, we're going to use our single molecule beginning temperature of 70F, we follow along the bottom bold line until we reach the 70F point and place a dot on our chart

image18945.jpeg
 
Once we have this second point ploted on our chart it unlocks the rest of the information that can be obtained from the chart. We can now find the dew point, an important temperature to know for humidity removal in high humidity locations and also if your dropping night time temperatures in your space to bring out colors. If we go straight to the left of our last ploted point of 70F and 50 RH to the dew point arched line it shows us about a 50F dew point. So any surface at or below this 50F temperature will cause our little molecule to contract to the point where it squeezes out some of its moisture ( condensation)

image18947.jpeg
 
So you can see that we can change our humidity by raising or lowering our temperature by a few degrees or we can lower the humidity by dropping our temperature below its dew point an then warming its temp back up to our 70F point. This same single molecule represents the million of molecules in our grow rooms and they will all behave in the same manor as this single molecule.

You can plot your grow rooms temperature and humidity and know for a fact what will happen by raising and lowering temperatures, know what cooling surface temperature is required to remove moisture to get your rooms humidity at the point you desire. There is much more information that can be extracted from the Psychrometric chart such as BTU's, wet bulb temperature,volume cu ft per pound of dry air, pounds of moisture. All information that can be useful to us depending on what we are trying to accomplish in our spaces.

We hope you find this information helpful for your grow rooms and have a better understanding of the relationship of temperature and humidity.

Blessed Buds our friends and be well :passitleft:
 
Posting to sub - and re-read when I'm less tired and stoned. Your pics are too low-res for me to read the numbers, but maybe that's not important.
Will be back. Thanks.
 
Weaselcracker said:
Posting to sub - and re-read when I'm less tired and stoned. Your pics are too low-res for me to read the numbers, but maybe that's not important.
Will be back. Thanks.
Click to expand...

We are so sorry for our photo quality, it's an old iPad so I'm sure it is part of our issue and me being the other part :-) not being so great at taking pictures. We appoligies for that :-(. Yes the numbers are important to see we will have to find a better camera one day soon.

Blessed Buds our friend and be well :passitleft:
 
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