One of the most commonly overlooked parts of setting up your indoor garden is accounting for the amount of moisture that will build up in your room from your plants transpiring.
Plants transpire about 97% of the water they receive, so the amount of water you remove from your room with a dehumidifier should be roughly equal to the amount of water you give to your plants each day.
Sizing your dehumidifier correctly from the start is very important to the success of your garden. Choosing an undersized dehumidifier will lead to mold, pest problems and powdery mildew among other serious issues.
Properly Sizing Your Dehumidifier For Your Grow Room
To determine what size dehumidifier your room will need to do some basic calculations. First, how much water are you giving to your plants each day?
For example, if your garden has 20 plants and you are watering with 1 gallon per plant per day, you will have 20 gallons of moisture to remove from your room.
Since dehumidifiers are rated in pints you need to multiply the number of gallons you give to your plants each day by a factor of 8 to convert to pints, which for this example is 160 pints of moisture you will be needing to remove.
If you are growing in soil and you only water every other day you will need to divide the total pints by 2 to get the average per day.
Sizing Your Dehumidifier For Hydro Systems
If you are using a hydroponic system you simply need to follow the same equation as above taking into account the water capacity of your system and any reservoirs that do not have a lid. The only difference is you'll divide the figure you get by 7 (days in a week).
This is because your plants won't be consuming all the water in your reservoir, so sizing your dehu under the impression that they would is going to be overkill.
Because you'll be changing out or topping off your reservoir every 7-10 days, you'll have to do some division to get a more accurate sizing. Our team has found that the above equation results in a better fit for hydro systems.
We recommend covering all reservoirs to prevent contamination and any additional humidity being added to the room.
Factors To Consider Along With Your Dehumidifier
Are you running a air-conditioner? If you have a sealed room with a/c, the a/c will remove some of the moisture itself.
Check your a/c to see how many pints per day it removes, and subtract that from your daily dehumidifying needs.
But, remember that your a/c will only be running occasionally. So when calculating size, make sure to play it safe and get a larger dehumidifier than you think you need. Under sizing is a common mistake newer growers tend to make.
If using CO2 in your room, it will increase the humidity levels. Also, if you are exhausting air from your room, the effectiveness of the dehumidifier will decrease. In either situation, consider to increase dehumidification performance.
Sizing a dehumidifier for a drying room
If you are sizing a dehumidifier for your indoor drying room, you may be under the impression that finding a huge dehumidifier can speed up the drying process.
You may be right, a dehumidifier will certainly dry out your buds fast. But this actually isn't what you want!
When it comes to drying your cannabis, low and slow is the mantra you should live by. Trying to dry out your buds as fast as possibe will suck the flavor, potency, and enjoyment from them.
But, if you have a decent sized drying room, you may need some level of dehumidification. You need to know the wet weight going in, and the dry weight coming out. Then, simply divide by 2. Here is an example:
If you bring in 1,000 pounds of wet cannabis, you can expect it to weigh around 800 pounds dry (200 lbs of water weight).
Dividing this figure by two gets you 400, which is the pints/day needed from your dehumidifier.
Then, you need to know the condition you are drying in, which should be around 65-70 degrees Fahrenheit. If you don't want to take any risks, reach out to us and we can make sure you get exactly what you need.
Final thoughts on sizing your grow room dehumidifier
Remember, sizing your dehumidifier is about how much water your room receives on average per day.
This will be approximately how much you will need to remove per day.
If you have additional questions or need help determining what dehumidifier will best fit your needs, don't hesitate to reach out.
If you haven't already, we recommend you check out our complete guide to grow room atmosphere and ventilation. It will give you a better understanding of whether or not you need a dehumidifier in the first place.