The biggest perk to growing in your basement is using the cold air to keep your tent cool. We can even manipulate the cool, somewhat humid air and simply heat it up to dry it out for dehumidification. We can use the geothermal cooling qualities of the earth to condition our grow tents!
Tent Conditions
The typical conditions for your tent vary between Vegetative state (70F,60%) and Flowering state (80F, 60%). Most un-insulated basements (no drywall) stay around 50F-60F, with the Relative Humidity varying all over depending on the basement. My basement typically stays in the 55-60F range and 45%RH. Because the basement is cooler and drier than the grow tent, you can use that air to cool your tent with just a couple of fans.
Cooling Strategy
To move the air from the basement into your tent, you can buy the fancy in-line fans like this AC Infinity fan that will regulate themselves and do a very nice job. Or, you can do what I do with computer fans for half the cost. I pick fans with 200-300 CFM and at least 0.5″ static pressure (ESP) to pull air through a carbon filter. Then I use a second fan with lower ESP to push air into the tent.
I use the two fan strategy to ensure I always have negative pressure in the tent to ensure the smell is removed by the carbon filter. To make this strategy work, you will need a decent filter with low pressure drop. I use the iPower Carbon Filters and they have been working great. I put each computer fan on a simple speed controller so I can balance them. Start with the exhaust fan, turn it on then slow it down until the tent is slightly getting sucked in. Then turn on the supply fan and turn it down until the tent walls are just slightly caving in again. Doing this ensures the airflow in the tent is slightly negative, meaning there is more exhaust air (through the carbon filter) than intake air and the odor will be controlled. This slight flow of air is enough to ensure there is “fresh” air with some CO2 in the tent at all times.
Controlling fans
Once the ratio of supply and exhaust air is balanced, put the supply air on a humidity or temperature controlled power strip like the Inkbird Temperature and Humidity Controller. This simply turns the supply fan on and off to maintain your set point. This isn’t the most precise way to control the climate in your tent, but it a very power efficient way to do it. It will be “good enough” to get the job done. This is especially true when you realize these two fans running together only consume about 20 Watts per hour. For comparison, an air conditioner consumes around 350 Watts per hour (assuming 4 plants using 1200 Watt HPS lights).
This is my favorite part of growing in the basement. We get a very small cooling bill, and the conditions around the tent are pretty consistent. This makes temperature control a piece of cake. If you would like help picking fans, comment below I and will help you pick some. I typically get mine from www.mouser.com, but picking the correct fan can get complicated and intimidating if you don’t know what to look for. I will explain more techniques for fine tuning temperature control in future posts, so stay tuned!
Thank you!!1