Grow Room Ventilation 101

Grow Room Ventilation 101

You may be motivated to have your own grow room. It may be that you want to grow your own produce at home. You probably have an interest in plants and their growth cycle. Whatever your reasons may be for starting a grow room, it can take some time effort to set up the grow room.

It is important that you set the best conditions for your plants. It is also important to do it in a safe way. Part of that includes a ventilation system. The size of your grow room determines the types of equipment you need as well as their various sizes. Keeping these things in mind can help you create a productive grow room.

Grow Room Ventilation 101

What is the Right Room for Your Grow Room?

When finding a space for your grow room, there are a few things to consider. The first thing you want to figure out if the space is big enough for your needs. You can use almost any space as a grow room. You can choose a room in your house, a cupboard, or a tent. The next thing you should think about is the power supply.

If you are only using one or two lights, two double wall sockets should be sufficient. You can even use an extension cord. You also want to think about your water supply. Avoid unfiltered rainwater because you don't know what is in the water. Instead, use filtered water.

Noise is another issue to think about. Your grow room setup can cause some noise. You have to think about how to cut down on the noise. Having the right flooring is essential for your grow room. Carpets can hold moisture. Bugs and bacteria can also thrive on carpets.

If you have a window in your grow room, you want to block it out. No natural light should be filtering into your grow room. Plants can get confused by inconsistent light.

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Grow Room Ventilation 101

Is It Necessary to Ventilate a Grow Room?

When plants are in their natural habitat, they are exposed to sunshine and wind. They also experience precipitation and evaporation. Although you may use fans, grow lights, and a watering system to replace these things indoors, you are still forgetting air circulation. When plants grow outdoors, they are experiencing air circulation as well.

This is necessary for keeping fresh air in your grow room. They are a few factors that keep the air in your grow room from remaining fresh. In order to make this possible, it is important to have a fan and an air extraction system.

Extracts Excess Heat

While grow lights are necessary tools in having a grow room, they can also emit heat. Although the amount of heat may seem negligible, a difference in temperature by a few degrees can mean a crop that is not as successful as a previous one. Some grow lights may even produce more heat than other grow lights. Regardless of how much heat is emitted from your grow lights, the heat they emit requires ventilation.

Keeps Humidity in Check

Humidity can cause issues with the plants in your grow room. Throughout the day, plants release water vapor. This causes the humidity levels in your grow room to increase. Left unchecked, high humidity can cause poor conditions for your plants to grow. It can also lead to your plants developing disease and attracting pests.

When you have good ventilation, some of that water that is released will be removed from the room. Not only will this make it possible for your plants to take in more water, but it will also increase the growth of said plants.

Keeps Diseases and Pests at Bay

Mold and mildew prosper in humid conditions. Gnats, spider mites, and fungus also do well in these conditions. Pests tend to use damp topsoil as a nest to lay their eggs. A fan will keep the topsoil dry. This can cause pests to slow down their reproductive cycle. It can also prevent them from establishing themselves due to the constant breeze from the fan.

Supplies a Constant Level of CO2

The main reason why plants need ventilation is because of CO2. CO2 is an integral part of a plant's nutrient cycle. If your grow room is sealed off, the CO2 level in the room will decrease. As a result, the growth of your plants will be limited. When you have good ventilation, fresh air and CO2 will circle into the room and push the old air out. Your plants will thrive because of this and increase their yields.

Strengthens Plants

Plants that grow outdoors are constantly being exposed to wind. Exposure to wind builds strength in the plants' stems. This is especially important for plants that bear fruit. When plants are weak, they will break from the weight of their yields. Creating good ventilation for your grow room will strengthen your plants.

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What are the Materials Needed for Making a Ventilation System?

Oscillating Fans

Oscillating Fans

Oscillating fans are not only affordable, but they are effective. You can use them to blow air all around your plants. They can be set up easily. You can also move them around. You can try different placements of the fans to see what is most optimal for growth. They keep the room cool and promote air circulation.

You want every part of your grow room to be exposed to the fans. So, you need multiple fans. It is important that the fans are not pointed directly at the plants. This can cause damage to your plants. You want the fans to emulate a gentle breeze.

Oscillating fans also help to control the humidity and temperature of the room. They are, however, just one component of keeping plants healthy in the grow room. An air extractor system is also beneficial for keeping the air fresh in your grow room.

Air Extractor Fan System

Air Extractor Fan System

With the air extractor fan system, old air is being pulled out and fresh air is being brought in. This process will allow your plants to thrive. You can set your system to extract air every minute, every three minutes, or every five minutes. It really depends on the fan size you choose. Pick one that is appropriate for your grow room.

Designing your grow room set up at the same time as your ventilation system is a good idea. Take the time to learn about ventilation systems before spending money on your grow room setup. You want to install your ventilation system at the same times as your grow room setup. This is so you don't have to change your grow system or work around plants.

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Grow Room Ventilation 101

How to Make the Calculations?

Fan Strength

When calculating the strength of the fan, some math is required. The ratings of fans are calculated by cubic feet per minute(CFM). In order to find out the CFM, you first need to figure out the grow room's volume. You can calculate this by multiplying the length, width, and height of the grow room. Once you have the CFM, multiply the efficiency drop by the CFM.

The make and age of the filter as well as the duct length from the fan to the filter determines the efficiency. There are some other factors as well. You basically want to multiply the room's volume by 25%. If your duct path is long, you want to multiply by three. For a short path, multiply by 2.

So, basically, this is the formula:

volume x efficiency drop = minimum CFM

Once you have the CFM, you want to find a fan that is higher than the CFM. High-intensity discharge (HID) lights, like HPS and Metal Halide, will increase how much ventilation is needed in the grow room. For each HID light, you want to add 5% to the CFM. This is only if the light is air-cooled. If it is not, you should add between 10% and 20% for each one.

If you are using a carbon air filter in your exhaust system, you should take into account that this will add to the friction in your system. You should add 20% to the minimum CFM. If your grow room tends to be hot, add 25% to the minimum CFM. If yo live in a hot and humid climate, you may need to add 40%.

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Grow Room Ventilation 101

How to Bring Air into the Room?

Passive Intake

When you rely on passive intake for ventilation, you are using negative pressure and passive airflow. So, the air is being blown out by a fan, but the air is not blown in. You put in an intake hole for new air to come in passively by the differences in pressure between the outside and the inside.

In order for the passive system to work, the intake hole needs to be three or four times bigger than the exhaust hole. The reason for this is so your fan won't overwork itself. It will also give the ventilation system the opportunity to attain proper suction. It also possible for you to have another intake hole.

Active Intake

With an active intake system, a fan draws air into the room. So, you have a fan to blow the air in and a fan for blowing the air out. It doesn't really matter how big the intake hole is. If you an intake hole that is the same size as the outtake hole, you may want to install an active intake system.

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Grow Room Ventilation 101

Why are Humidity Levels Important?

Humidity levels are an important part of plant health. When the grow room is too humid, disease can thrive there. It can also impede plant growth. Therefore, it is important to monitor the humidity in the room.

Humidity is caused by transpiration. Transpiration is when plant leaves release water into the atmosphere. Transpiration allows nutrients to be pulled up through the roots. This causes the plant to release water vapor.

This explains why plants that dry out stop growing. When they don't get an adequate amount of water, they are also not getting the nutrient they need to grow. Excessive humidity can also pose this problem. It creates the right environment for pests and diseases to grow. It also stops evaporation from occurring which also reduces transpiration. You, therefore, need to be able to easily adjust the humidity levels in your grow room.

In order to lower humidity, you can use the exhaust system to vent out the humid air. This requires that the new air you are bringing in has less humidity than the air in the grow room. You can put a dehumidifier in the room.

There may be times when your plants require more humidity. In order to increase humidity levels, you can seal your grow room. You can also turn off the exhaust system. This will increase the humidity in the room pretty quickly.

To find out what humidity levels are appropriate, you may have to do some research into what levels allow your crops to thrive and keep them within those levels. Keep in mind that large plants will release more water vapor than small ones. So, as your plants continue to grow, you will have to watch the humidity levels.

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Grow Room Ventilation 101

What About CO2 Injection?

Since plants need CO2 for transpiration, it makes sense to inject CO2 into the grow room as a way to boost plant growth. Although this is true, there are some things to consider before injecting CO2 into the grow room.

You will have to first seal your grow room. The reason behind this is efficiency. In order for the injection to work, the CO2 needs to be at a very high level. Sealing your grow room will allow the concentration of CO2 to get high enough, making it worthwhile.

The next thing you need to consider is safety. A high level of CO2 can be dangerous for humans. You want to make sure the CO2 is not leaking out of the grow room into the rest of your home because this can cause risk to yourself and your loved ones.

You also want to make sure you have bright grow lights before adding the extra CO2 so that your plants can really use the CO2 most efficiently. With strong LED lights and MH/HPS lights, you will have enough light for your grow room. If you have FLs or T5s, they are not bright enough for the results you want.

When deciding to inject CO2, you will have to consider if it is really something you can or should do. If the pros outweigh the cons, then do it. If you are happy with the number of crops you are already producing and your budget is limited, you don't need to do CO2 injection.

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Grow Room Ventilation 101

How to Deal With Noise Pollution?

Using fans in your ventilation system will cause some noise. If you are working in your grow room, you may find the noise irritating. You may also annoy your neighbors with the rumbling of the fans. Choosing the right components and taking other measures, however, can help keep the noise in your grow room to a minimum.

Choosing a fan with a CFM rating that is 25% higher than what you require will allow you to run the fan at a slower speed. Not only will it be less noisy, but you are still getting the performance required to keep your grow room at healthy humidity levels. You can also install soundproofing to deaden the sound made by the fans. For your active exhaust fan, add a silencer to reduce the sound of intake. Using insulated ducting as oppose to regular ducting can also reduce the noise made from the wind.

What are Some Things You Can Use to Make Life Easier?

Fan Controllers

Although the basics for a grow room have been covered, there are some other tools and materials you can use to help with efficiency and make your life easier. Fan controllers are a good tool for making your grow room more automated. When the room gets too hot, the fans will speed up. If the grow room is too cold, the fans will slow down.

When the lights are on, you want to aim for temperatures between 75°F and 80°F. If the lights are off, the temperature should be between 69°F and 75°F. Make sure you are extracting enough air to keep the CO2 levels in the grow room and the humidity under control. You also want to make sure the negative pressure is maintained. Keeping the fan speed between 10% and 30% is good for most grow rooms.


Extracting air in the winter can cause your grow room to become too cold. Using a grow room heater can mitigate this. Some heaters are made to heat large areas in a rapid amount of time. They may even have a thermostat built-in so you can heat the grow room automatically.

Humidity and Temperature Meter

Having a meter that monitors the humidity and temperature in your grow room will also make things easier for you. It will also let you know the conditions your plants are growing in. For humidity, you want 70-85% in relative humidity (RH) during propagation. As it is growing, it should be 65-75% RH. Once your plants are flowering, it should be between 45% and 65% RH. When the lights are on, the optimal temperature should be between 75°F and 80°F. When the lights are off, you want the temperature to be between 69°F and 75°F.


High humidity is beneficial for plants during the propagation and vegetative growth stage. Extracting air may be necessary for keeping the temperature and CO2 level in the grow room under control.

However, this can cause the humidity to drop to a level that is too low. Summer is usually the season when this happens. A humidifier can help with this situation. You may also want to mist your plants with a sprayer.

Grow Room Safety

Grow lights, for the most part, are safe. Like most electrical items in your home, they only require a couple hundred watts. You just need some common sense. Cable ties are a great tool for keeping wires tidy. They also keep the wire out of the way so you don't trip on them.

You also want to make sure electrical devices aren't exposed to water unless they are supposed to. Any equipment should not be accessible to children or pets. Read all instructions and safety manuals. Have a fire extinguisher in your grow room. Unravel reflector cable as they can get hot.

The Wrap Up

Setting up your ventilation system in the right way can help improve the health of your plants. The best this is to set up your ventilation system at the same time you are setting up your grow room. You also want to figure out if you want to set up a passive intake system or an active intake system.

You also want to think about if CO2 injection is right for you. Choosing the right size fans can also help with transpiration and reduce noise pollution. When you take these necessary steps, you will have successful yields.