Think about taking a walk in the park or hiking a mountain: all of the plants around you will be moving in the wind. This is a kind of natural ventilation. However, in an indoor gardening room or tent, we need to recreate natural conditions that won’t be possible without the right equipment and planning. We’ve talked a lot about LED grow lights but we also want to cover the specifics of ventilation in a grow tent.
Using grow lights can create a lot of heat in a small space like a grow tent (although LEDs create less heat than HPS or MH bulbs!). Sometimes, the inside of a tent can reach above 80 degrees, which can be very harmful to your plants. Further, lights produce both convective and radiant heat so you may find that your tents get a lot hotter than you planned—this is why we also recommend picking up a thermometer when growing in a tent.
Plants are constantly emitting water vapor along with Oxygen and CO2 as byproducts of photosynthesis. Since you are growing in an enclosed space with stagnant air, the built-up moisture can attract pests and encourage mold. Good ventilation can effectively reduce the humidity inside the tent, and a high CFM fan helps control it.
This might be the most important role of a fan!. Plants need a lot of carbon dioxide-containing air for photosynthesis, but a confined space obviously adds any extra CO2, so fans solve this problem by bringing in outside air and forcing old air out of the tent.
OK! Now we know why a fan is important for your tent, but how often should we run it? There are a couple of things to consider.
Different sizes of grow tents require different amounts of ventilation. Divide the tent’s volume by 3 to get the desired CFM (cubic feet per minute). If you own a grow tent about 720 cubic feet in size, you need a fan with 240 CFM.
In general, growers estimate the following equipment to add higher CFM requirements to your fan:
Ducting: For each 90° bend in your ducting your CFM requirement will increase by about 40-60%, so try to minimize the number of bends in your ducting.
Carbon Filter: A carbon filter will increase your CFM requirement by about 60%.
Grow Lights: Due to heat output, your CFM requirement will increase by about 50% for LEDs.
Now, with all of this information, we can measure the approximate CFM required for our fan. The equation will be:
(cubic feet of space) x (ducting) x (carbon filter) x (grow lights) = CFM required.
107 x 1.6 x 1.6 x 1.5 = 410CFM
Tent size CFM required 24” x 24” x 36” ~46 CFM 24” x 24” x 48” ~62 CFM 32” x 32” x 63” ~135 CFM 36” x 20” x 63” ~95 CFM 36” x 36” x 72” ~207 CFM 48” x 48” x 80” ~406 CFM 60” x 60” x 80” ~634 CFM 48” x 48” x 72” ~369 CFM 60” x 60” x 72” ~576 CFM 96” x 48” x 72” ~737 CFM 96” x 48” x 80” ~811 CFMOnce the light is on, the best practice is to have your fan running. Luckily, most fans come with some kind of speed controller so you can adjust the CFM according to your needs—how hot your tent is, how much airflow your tent has naturally if you’re using oscillating fans (we’d recommend using them at max speed), and how humid your tent is.
During the night cycle when your light is off, the temperature inside your tent will gradually decrease as the light is no longer producing heat. Yet, you’ll still need your fan to run for a while to help circulate air. If you are using an inline fan, we recommend you begin to reduce the speed of your fan 20 minutes after you have turned off your lights, and, over the next few hours, continue to reduce the fan speed until after about 3 hours, you can turn it off entirely.
For oscillating fans, we recommend that you slow the fan speed down during the night cycle, but keep it on overnight.
When plants are in their seedling stage, they tend to be fragile.
At this time, we recommend you run your fan 24/7 to maintain temperature, humidity, and fresh air inside the tent.
In addition to an inline fan, we also recommend having a gentle oscillating fan in your tent. Do not point the fan directly at the seedlings, they are fragile!
The goal during the seedling stage is to have a very gentle breeze while keeping the air humid enough for your seedlings. If you are doing it right, your seedlings should not really need to be watered, just misted, and you can provide them with a gentle breeze during this early period.
At this point in your plants’ growth, they should be strong enough to withstand proper, heavy airflow—this encourages stronger, more resilient plants! Keep your inline fan speed on max so that airflow passes through your plants’ canopies. During the night cycle, try the slow-down technique we outlined in the Light/Dark hours section. During this stage, we still recommend using an oscillating fan.
The final stage of growth is a little different than the vegetative stage. We recommend you run your inline fan all the time during the day, and turn it off an hour dark after you turn off the lights. This will allow your plants to bloom undisturbed.
In short, ventilation and air circulation are crucial to improving the health of your plants. Your ventilation cycle can vary by plant, but we hope this guide can save you a bit of time when first starting out.
As always if you have any questions you can message our Instagram or Facebook and we’ll be glad to help you out! We’re happy you’re on this journey and we want to help in any way we can.
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VIVOSUN AeroZesh: Fully Controllable Ventilation
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All You Need to Know! VIVOSUN Smart Grow System FAQs 2022
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If you've ever had to deal with a bathroom that lacks a working fan or window, you know exactly how unpleasant the experience can be. Odors, normally whisked away in just a few minutes, may linger for much longer, whether from poop or powerful bathroom cleaning products.
But moisture is the real enemy. Humidity from showers fogs up the mirror and leaks into walls. As the warm air cools, it turns into water, and gets trapped in the walls.
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"Indoor condensation can lead to mold growth," says Dave Bayne, CEO and owner of A1 Mold Testing & Remediation. "Drywall is porous and paint is breathable, so the moisture can seep into the drywall and create fungal growth," often in places where you can't see it.
If you're exposed to mold long enough (or if your body is allergic or sensitive to its spores), the Centers for Disease Control and Prevention indicates that you may suffer a laundry list of ill effects, from allergies to coughing to skin irritation.
Excessive moisture may also cause peeling paint and wallpaper and even contribute to warped doors and rusted fixtures. Dampness also fuels bacterial growth and other nasties.
By simply turning on the bathroom fan, you minimize a lot of those problems. "You should turn the fan on each time you run water in the bathroom and leave it running for about 20 minutes after you open the [bathroom] door," says Bayne. The most important time to do this is after you shower. If you're continually forgetting to turn it off, install a fan timer. And though it's seldom done, the fan should be cleaned at least yearly.
If you're a homeowner, be sure that your fan is properly vented directly to the home's exterior via an insulated duct. "It was common in the '70s and '80s for it to be vented into the attic space," says Bayne. "Building codes today require that the exhaust is vented outside through insulated ducting to a roof vent that goes directly to the exterior." Otherwise, you may be contributing to moisture and mold problems in your attic or wall spaces.
If you don't have a bathroom fan, most building codes in the U.S. specify that there must be an operable window to allow for better airflow.
Now That's Interesting
Bathroom fan noise isn't rated by decibels; instead, it's rated in sones. A 1-sone fan might sound like an average refrigerator, while a 5-sone fan might sound like a jet aircraft is about to burst through your medicine cabinet. So if your fan is too loud you may be able to find a quieter one that can still do the job.
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