Grow Room Ventilation 101

Ed Wike
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Why Do You Need to Ventilate Your Grow Room?

It’s important to properly ventilate your grow room as fresh air exchanges are beneficial to plants.

The primary reason behind this is that fresh air contains carbon dioxide. CO2 is what helps the plants grow and various factors can decrease it levels in your grow room.

Here are a few reasons why proper ventilation is important:(1)

Carbon dioxide levels can get depleted due to drafts. Excessive wind in the room can reduce the CO2 levels because it’s forcing the air in the room to move, thus pulling CO2 out.

Carbon dioxide levels can also drop as the plants release the gas. Even if you only have a few plants, they will still release some carbon dioxide.

Too much air in the grow room can dissipate the CO2 as well. There are various factors that cause this such as air evaporating on the plants, air coming from an air conditioner, and heat from lights.

Remove Excess Heat

Heat from your lights, the room itself, and your grow lights will cause your temperature to rise. If it gets too high, it will kill your plants. You may want to consider using carbon dioxide generators to increase the air's CO2 content.

Your grow lights create a lot of heat, and the heat builds up in your grow room. You want to get rid of this excess heat in a way that protects your plants. If you don't, you risk your plants getting stressed. If they get too warm, they'll start to cook. That will cause your plants some serious problems.

Control Humidity

At this point you’ve got a weed farm that’s set up and you’re ready to start growing some marijuana. Now let’s take a look at some of the ventilation options for your grow room!

Prevent Pests and Diseases

If your grow room isn’t temperature regulated, you need to ensure that you’re not using the same ventilation system to cool your crops as you are to oxygenate them.

Note that 95% of your indoor marijuana plants need air that is at least 25% carbon dioxide to germinate. Most of the CO2 that indoor marijuana plants get is produced by plant respiration.

It is important to avoid getting too much air movement near your plants or you can create turbulence that can damage the plant’s trichomes.

Another important reason to control the temperature of your grow room is to help you fight off pests and diseases.

Having a slide in thermostat installed on your air handling unit means you can program it to keep the temperature inside your grow room at the desired temperature and within a few degrees of accuracy.

You should bear in mind that especially for seedlings and young plants, an excessively hot or cold environment can make the difference between life and death.

Control CO2

One of the most important things to get right for a successful grow is ventilation. It’s important to keep the temperature in your grow room well regulated. This enables your plants to flourish and have that sweet sticky THC resin that we all want.

The two main functions of ventilation are temperature and air movement control. The more movement you have, the more CO2 your plants will consume, but the more exhaust and heat your room will create.

If you have too little air movement, your plants will succumb to poor ventilation and stale air, which can trigger a myriad of nasty conditions and health ailments. That being said, you want to avoid creating a draft that will cool off and/or dry out the floor surrounding your plants. You want to create a comfortable environment for your plants with the perfect amount of ventilation. If you live in a humid area, you’ll need to run humidifiers to offset the dry air you introduce into the grow room.

Manage Wind Stress

Cannabis plants require lots of ventilation and CO2 management, and as the grower you have to decide how much ventilation is enough.

Without proper ventilation, cannabis simply won’t grow. Much debate and disagreement has broken out about the optimum amount of ventilation needed for cannabis to thrive. Over-ventilation is often maligned by the cannabis community and growers alike, while under-ventilation is somewhat overlooked, or even worse, accepted. This is a huge issue for indoor cannabis growers because proper ventilation is essential to obtaining huge yields and preventing harmful bacterial buildup. Under-ventilation will lead to plants more susceptible to disease, slow growth, slow flowering, and smaller yields. Properly managing the amount of ventilation allows you to achieve the best yield with the least amount of stress.

How to Ventilate Your Grow Room

Ventilation is an important part of your grow room equipment. Ventilation that's too powerful can dry out your plants and create a draft. A ventilation that's insufficient can cause your plants to suffer from mold, mildew, and rot.

Your goal should be a tight and efficient system that maintains the temperature and humidity levels you're seeking. A good ventilation system will also minimize additional stressors, such as sound and light leaks.

You can achieve this by considering the following:

The circulation of air in the room must be increased. By increasing the air circulation and creating positive air pressure, air will be forced into the room, rather than trying to escape.

The temperature and humidity levels must be kept within a comfortable range. Even with an exhaust fan, it's easy to keep the temperature and humidity out of balance. Make sure the air is being vented out of the space and not brought back into the space.

Keep windows closed to reduce the amount of air exchange in the room. It's best to avoid bringing in any unfiltered air. Allowing outside air to enter the space may get in pathogens, pollen, and other airborne pollutants.

You will also need to know how to size the fans properly. Overpowered fans can cause speeding within the grow room which can be as damaging as stagnant air. The exhaust fan size should be about 100% – 130% of the size of the intake pipe.

Place Oscillating Fans in the Grow Room

Ventilation is something which is related to the temperature of a room. It is imperative to have an optimal temperature in the grow room, so the plants don’t get burnt in the beginning and the temperature doesn’t go down by the end. It requires careful planning and management.

As your plants grow in the grow room, they will keep producing CO2. This causes the room to heat up. So you need to have fans that point to the wall so the air flows out.

You can also place oscillating fans in the grow room which help cool your plants. You can point them towards the grow room.

Air Extractor Fan System

The air extractor fan is one of the most important pieces of grow room ventilation equipment and it is usually the largest piece. In fact, for the machines that extract air at 120° F–upwards of 300 feet° F, the air extractor fan is a solid metal construction with a durable powder coat finish.

As for the size of the air extractor fan, it depends on the size of the grow room where the fan will be used. Mostly, the sizes you can choose from are 600, 800, 1,000, and 1,500 CFM. These numbers usually refer to the maximum voltage and airflow capacity of the equipment.

The most common size for small rooms is 1,000 CFM. Larger ones tend to be 1,500 and 2,000 CFM. Again, these are just recommendations. Depending on the size of the room, you can decide whether a smaller or larger air extractor fan is appropriate.

Regarding the operation of an air extractor fan system, the flow of air goes like this.

The air comes from the vent, the duct, or the exhaust fan.

It passes through one or more filters, which then passes through a fan, which then passes through the duct, and finally to the grow room.

The fan has a duct that carries the air from the extractor to the plant.

Controlling Humidity

If you're a pothead and you're growing weed under lights, then you know that a good grow room needs proper ventilation.

You may even know that you need to sweat the room and not ventilation with an exhaust fan alone.

But did you know that the direction you ventilate your grow room will affect your humidity?

[SAL] The Basics:

You let hot air out and cold air in. The cool air gives your plants a comfortable environment to grow.

There is more to it than that, however.

Humidity is the most important factor in growing marijuana.

You know the environment too dry may stunt the growth of your marijuana plants. But you might not know that a room too humid can also stunt the growth of your marijuana plants.

So let's learn how to control humidity when growing weed under lights.

[FILL]Since you are reading this, you probably have some experience in growing pot under lights.

So you know too much carbon dioxide can lead to disaster for your marijuana plants.

[FILL]You have probably also learned that your newborn marijuana babies must be protected from any and all light.

[FILL]You are probably also aware that you must keep the air inside your grow room fresh.

All of your marijuana plants require a proper CO2 level, proper PH level, and proper air circulation to thrive.

CO2 Injection

One of the most important factors that control the growth and yield of plants in a grow-room is fresh air. After that comes good light, and after that comes the quality and the quantity of the water and the nutrients you give the plants.

For watering purposes, plants have their natural root system and you have this system of pipes connected to a water pump and you pour water into a tank and it goes up the pipes to the plants. They have this natural place to take water from. Now the air is another matter entirely. You have to pump air into the grow room in order to allow the plants to breathe.

To achieve proper ventilation of your grow room, you'll need a fan and a filter to remove the air. This is usually done in such a way that when the fan is switched on, it blows out warm, stale air. This air is then pushed out of the grow room, and new, fresh air is drawn in to replace it.

Depending on the size of your garden and what type of plants are growing there, you'll need to have a very large fan capable of moving many cubic feet of air out of the room every second.

Grow Room Ventilation FAQ

Ventilation is a must for any grow room. All of the best LEDs and grow lights in the world won’t make up for a lack of good circulation and ventilation. CFM (cubic feet per minute) is the measurement to use when researching your grow-room ventilation. CFM is the amount of air circulated per minute and is a standard unit of measurement of the interior airflow.

You can calculate CFM using the following formula:

CFM = (square footage x noise percentage) / exhaust fan efficiency

The size of the exhaust fan and overall efficiency are important factors, since you will of course be running it more often. Here are some helpful guidelines:

1-2 plants (low humidity): 1,000 cfm and below

2-3 plants (medium humidity): 1,300 cfm and below

3-4 plants (high humidity): 2,000 cfm and below

5+ plants (high humidity): over 2,000 cfm

You can use a 1,000 cfm for each square-foot of your grow room, but the last thing you want to do is over-exhaust your plants. Your cannabis plants are holding their breath and panting to make as much energy as possible. Over exhausting them will disrupt their photosynthesis, stunt their growth, encourage vegging and make it difficult to flower the buds.

Go Forth and Ventilate!

Lighting and air flow are the two most important factors in the production of healthy marijuana. Ventilation is one of the most important elements to consider. There are a few reasons why you must always have a vent on your grow room. The first is security (not everyone is as awesome as you are), and another is to provide life-giving air to the ecosystem. The second is to prevent the growth of mold, fungus, and bacteria.

The first step to setting up a venting system is to measure the ventilation you'll need for all your fans. The main goal is to have a well-ventilated grow room. Make sure that the system you have in place gets as much fresh, cool air as possible. Fresh air needs to be brought in constantly. If you regulate the temperature, you'll want the air to be cool, and if you keep the temperature steady, you must keep the air fresh. Make an overlay of your grow room and over that lay out push pins. These push pins need to measure the location of your air inlets and outlets.