When you’re planning an indoor garden, there are some important things you should consider, one of them is ventilation system. Regardless of the growing space you use, whether a grow room, grow tent or even a grow box, it will require a ventilation system. The ventilation has an important role to create a perfect and suitable growing environment for your indoor plants. And in this article, “Grow Room Ventilation System”, we’ll help and guide you to setup a good ventilation system in your grow room or tent.
Imagine this: What will happen to your indoor plants if you have a bad ventilation system or no ventilation system at all in your grow room or tent?
That’s right, your indoor plants won’t grow healthy, and eventually they’ll find it hard to survive. No doubt about it!
If you’ve read this article, ‘Indoor Grow Supplies’, you certainly know how important the grow room ventilation system is. Because besides the lights, the indoor plants need fresh air, carbon dioxide (CO2), proper temperature and humidity to grow and thrive. Those elements will be available if you’ve a good ventilation system in your indoor grow room or grow tent.
But before building or setting up a grow room ventilation system, let’s learn the basics first.
Table of Contents
- 1 What is Ventilation System?
- 2 Grow Room Ventilation System, It’s a Must!
- 3 4 Benefits of Having a Grow Room Ventilation System
- 4 2 Types of Grow Room Ventilation Systems
- 5 The Right Fan for Grow Room Ventilation System
- 6 Grow Tent Ventilation Setup
- 7 Grow Room Ventilation Setup
- 8 Grow Room Ventilation Tips
- 9 Conclusion
What is Ventilation System?
Definition in indoor gardening — A system that allows air circulation inside the grow space to keep it fresh and cool. This means the system will replace stale, smelly and hot air inside the grow space with cool and fresh air.
Here’s the thing:
The grow room ventilation system in this context basically consists of 3 to 4 components only. Here’s the basic equipment for ventilation.
- Intake fans
- Exhaust fans
- Oscillating fans
However, sometimes some growers need additional equipment (advanced ventilation system), such as air conditioners, dehumidifiers and CO2 enrichment equipment. This is because they have a different indoor grow room or tent setup.
We’ll discuss it further later.
Grow Room Ventilation System, It’s a Must!
As we’ve mentioned earlier, the grow room ventilation system has a vital role when you are growing indoors (indoor gardening). In other words, you must have a ventilation system in your grow room or grow tent, a good one. Why?
Your plants that are in the indoor garden, whether it’s a grow room, grow tent or grow box, need the elements that we’ve mentioned earlier. The ventilation system controls those elements, which it brings in fresh air along with CO2 regularly into the grow space. Your indoor plants then use it to support their lives, including photosynthesis.
The bottom line: Grow room ventilation system will provide fresh air, CO2 and breeze for your indoor plants. While those elements are freely available when the plants grow naturally outdoors.
Great things will happen if you have a good ventilation system in your indoor garden.
4 Benefits of Having a Grow Room Ventilation System
Here are the main reasons why the indoor grow room or tent must have a good ventilation system:
Just like humans, plants need the elements that exist in the air to survive. If humans need O2, then plants need CO2 instead. When you grow plants in enclosed environments, you must provide them with CO2 in the right amount regularly. If not, the indoor plants will stop respiring and they’ll die slowly, just like us without O2.
The first benefit of having a grow room ventilation system:
As we mentioned earlier, the ventilation system will bring in fresh air along with CO2 from outside into your indoor garden. With the continuous supply of CO2, it can ensure the plant’s photosynthesis is not compromised.
Here’s an interesting thing:
The use of indoor grow lights may affect the use of CO2 in plants. If you’re using HID or LED grow lights (bright and intense lights), the indoor plants will be able to absorb more light and CO2, which will increase their photosynthesis. This means allowing the plants to produce more energy to grow faster and provide greater yields.
If you need a reference about indoor grow lights, please take a look at ‘Indoor Grow Lights’ section in this article: ‘Indoor Grow Supplies’.
Control Heat and Temperature
As we know, we use indoor grow lights instead of direct sunlight when growing plants indoors. Without us knowing it, those lights produce heat, even though the amount of heat emitted by the lights may vary. For example, HID lights will emit more heat than LED grow lights. While fluorescent lights will emit less heat than those two lights.
Here’s the problem:
If left unchecked, the indoor grow lights will slowly increase the temperature and heat up your indoor garden. Remember, indoor plants will grow and thrive in a certain temperature range, which is between 68°F (20°C) to 84°F (29°C) — a comfortable range for most plants.
The second benefit of having a grow room ventilation system:
The ventilation system will remove the excess heat produced by indoor grow lights. Moreover, it will also help you control the temperature and prevent lights from overheating your indoor garden.
For measuring the temperature of your indoor grow room or grow tent, you can use analog or digital thermometers. It will be great if you’ve some thermometers and place them in various locations of your grow space.
Control Humidity and Pests
While the indoor lights emit heat, it turns out that the plants also emit something, water vapor. This means the humidity level in your indoor garden can increase. Humidity is good actually, if at the right level. But if the humidity level is too high, it can lead to the development of mold, mildew and fungus.
It’s not only that, high humidity will also attract pests apparently. As you might know, pests multiply in the damp or moldy environment, which they lay their eggs in damp topsoil.
The third benefit of having a grow room ventilation system:
Besides removing the heat emitted by the lights, the ventilation system also removes this moist air from inside your garden. The dry air will replace the moist air, which prevents the development of mold and mildew, and the reproduction of pests in your indoor garden.
You can also increase or decrease the humidity level in your indoor garden by using a ventilation system.
For measuring the humidity in your indoor grow room or grow tent, you can use analog or digital hygrometers.
Strengthen the Stems of Indoor Plants
When you’re growing plants indoors, of course you want your plants to grow healthy and strong. Strong on every part of the plant, including stems, which are indispensable for tall plant. As you know, when plants grow outdoors, the natural wind hit them continuously. The wind makes their stems stronger so that their stems can bear the burden of flowers or fruits later on.
The fourth benefit of having a grow room ventilation system:
You can strengthen the stems of your indoor plants by providing a gentle breeze from the oscillating fans. With the hope that your indoor plants will grow upwards without bending.
2 Types of Grow Room Ventilation Systems
In this context, there are two types of ventilation systems for indoor grow room or tent that we know so far.
Let’s break it down.
Passive Intake Ventilation System
This type of grow room ventilation system relies solely on negative pressure and passive airflow in your indoor garden. That’s why it’s called the ‘passive intake ventilation system’.
Here’s the kicker:
This system uses only one exhaust fan to remove smelly and hot air from inside your grow space. And there is no intake fan to bring in fresh air from outside into your grow space.
You may be wondering: How to supply fresh air into the indoor garden then?
In this system, you’ll use an intake hole to bring fresh air into your grow room or grow tent passively.
This passive intake system will work if:
You have a larger intake hole, maybe 3-4 times larger than the exhaust hole in your grow space. Moreover, you can have more than one intake hole in your grow space, not just a single hole.
But keep in mind, you must calculate the pressure differential you have between inside and outside the grow space. This is because the pressure inside and outside the grow space will keep the balance of airflow into the grow space.
The bottom line: You must understand how negative pressure works in your indoor garden.
Active Intake Ventilation System
We think you already know this system.
This type of grow room ventilation system uses two types of fans for air circulation in your indoor garden, exhaust and intake fans. The exhaust fans will remove the excess heat and stale air from your garden, while the intake fans will bring fresh air into your garden. These fans will actively pull in and pull out the air, which is why it’s called the ‘active intake ventilation system’.
Here’s the best thing about this active intake system:
Unlike the passive intake system, you don’t have to worry about the size of the holes you have in your grow room or grow tent. Even if you’ve holes with the same size, this system can still work very well and efficient. In addition, this system will also reduce the amount of negative pressure in the grow space. This means allowing much more air to pass through and reducing the exhaust fan workload.
This active intake system is very often used by indoor growers and easily found in any indoor garden these days. Therefore, this system will be our reference for building or setting up the ventilation system in this guide.
Here’s the deal:
In order for this ventilation system guide to be clear and detailed, we’ll setup a ventilation system for two types of grow spaces. The first is 4×4 grow tent ventilation setup and the second is 6×6 grow room ventilation setup. We believe this ventilation system won’t cost you too much, which is practically ‘a cheap ventilation system’.
Sounds good, right?
And do not worry because we’ll discuss them one by one, layer by layer. Once you understand the role of all the ventilation equipment, this will make it easier for you to build or setup a grow room ventilation system. You can combine these components together according to your ventilation design to create a good ventilation system in your indoor grow room or tent.
Wait, still don’t have a grow tent for indoor growing? Check out this article: ‘Best Grow Tents’.
Before going to the interesting part of this guide, we want to show you some important points about the intake and exhaust fan.
The Right Fan for Grow Room Ventilation System
According to the above definition, you need a good ventilation system to create air circulation in the indoor garden. This means you have to provide a steady supply of fresh air for your indoor plants on a regular basis.
The question: How often you have to change the air (air circulation) in a grow room or grow tent?
In our opinion, ideally, you should replace the air inside the indoor grow room or tent every 1-3 minutes. However, we tend to replace the air every minute since we live in a pretty hot place. So in order to create a good ventilation system, first, we need at least one strong exhaust fan for the exhaust system. This system has a function to remove the stale and smelly air from inside the grow room or tent.
Now you may be wondering:
What size of exhaust fan is needed for an indoor grow room or grow tent?
How to calculate exhaust fan strength (CFM) for a grow room or tent?
The Size of Exhaust Fan
For the size of exhaust fan, we often use a 4″ or 6″ fan in small and medium setups. For large setups, especially a large grow room, we often use 6″ and 8″ exhaust fans.
But to be more sure, you have to calculate the CFM of your indoor grow room or grow tent. The calculation results can determine the size of the exhaust fan you need for your grow space. Take a look at the section below.
How to Calculate Exhaust Fan Strength (CFM)
In order to calculate the strength of exhaust fan (CFM), indoor growers usually have their own calculations. If you type “grow room ventilation calculator” in search engines, you’ll find several different formulas to calculate CFM for an exhaust fan.
In this guide, we’ll use a simple formula, which is calculated by multiplying the volume of the grow space with efficiency drop.
So let’s get into the detail.
First, calculate the room volume in cubic feet by multiplying length x width x height (L x W x H) of your grow space. After you get the number, the next step is to multiply that number by the exhaust efficiency drop. Here’s a good rule of thumb for the exhaust efficiency drop:
- Multiply the room volume by 2 — if you have a short and efficient duct path, which air goes through a short, straight path after leaving the fan.
- Multiply the room volume by 3 — if you have a long duct path, which air goes through a long, twisting path after leaving the fan.
The above formula will look like this:
Room volume x Efficiency drop = Total CFM
That’s it! We have a total CFM rating now. The next step is to choose an exhaust fan that has a CFM rating higher than the total CFM. This is because we need to compensate for air resistance in ducting. That’s why it’s always better to over-spec exhaust fan.
Here’s another formula if you want to calculate the strength of exhaust fan (CFM) in a different way.
You can use the Dan’s Method to calculate the lowest CFM rating needed for the exhaust fan.
Using too many formulas to calculate the CFM rating, it might confuse you. This is because each formula will produce different CFM numbers.
The Size of Intake Fan
For the size of intake fan, you can use a fan that has the same size as your exhaust fan. But the intake fan strength should not be equal to the exhaust fan strength. The intake fan you use should have half strength of your exhaust fan.
If you use a 6″ exhaust fan with 440 CFM, then you should use a 6″ intake fan that has a rating of about 220 CFM.
Grow Tent Ventilation Setup
Please note, as we mentioned earlier, this is a step by step guide to building or setting up a ventilation system in a 4×4 grow tent. For larger or smaller tents than this, the grow tent ventilation system or setup may be different.
For your information:
In this case, the indoor grow tent size is 4′ x 4′ x 6.5′ (L x W x H). We have 2 x 150W HPS lights and 1 x 800W LED light. So we have 1100 watts in this 4×4 tent. We want the air in the tent to change every minute. Lastly, we have a pretty long duct path.
Based on the calculation or formula above, we get a total CFM rating, which is 312 CFM, to ventilate this grow tent. In this situation, we’d choose a 6″ exhaust fan with 442 CFM, iPower Inline Fan. Then we combine this fan with a 6″ 442 CFM carbon filter, Amagabeli, to create a complete exhaust system for this grow tent.
Here’s an example of a complete exhaust system in the grow tent:
If you use non-air cooled lights, which they don’t have a hood (air-cooled reflector), such as T5 and LED grow lights, the exhaust system will look like this:
This is what we get when running the grow tent ventilation system as above:
- When the grow lights are on, the ambient temperature is in the range of 77°F to 79°F.
- When the grow lights are off, the ambient temperature is about 74°F.
- The humidity is around 50 – 60%.
Here are the pictures of this grow tent ventilation setup:
Complete Grow Tent Ventilation Kit
Here’s a complete list of ventilation system equipment for the above 4×4 grow tent.
- 1 x 6″ Exhaust fan : iPower Inline Fan 442 CFM + Fan speed controller
- 1 x 6″ Carbon filter : Amagabeli 442 CFM
- 6″ Flexible aluminum ducting + clamps
- 1 x 6″ Intake fan : Urban Farmer Inline Duct Booster Fan 240 CFM
- 2 x Clip oscillating fans
Additional equipment (optional):
- 6″ HEPA filter
- Bug Screen
For a complete guide on how to setup a grow tent from the beginning, please take a look at this article: ‘Grow Tent Setup’.
Grow Room Ventilation Setup
Please note, as we mentioned earlier, this is a step by step guide to building or setting up a ventilation system in a 6×6 grow room. For a larger room than this, the grow room ventilation system or setup may be different.
Here’s the thing:
As you might know, there are two types of indoor grow room: vented and sealed grow room. Unfortunately, each type has a different grow room ventilation system, as well as the equipment to be used. In this case, we’ll setup a ventilation system for the vented room.
For your information:
The indoor grow room size is 6′ x 6′ x 7′ (L x W x H). We have 1 x 1000W HID light (air cooled light). We want the air in the room to change every minute. Lastly, we have a short duct path.
Based on the calculation or formula above, we get a total CFM rating, which is 504 CFM, to ventilate this grow room. In this situation, we’d choose a 8″ exhaust fan with 745 CFM, Hurricane Inline Fan. Then we combine this fan with a 8″ 730 CFM carbon filter, Vivosun, to create a complete exhaust system for this grow room.
Here are the pictures of this grow room ventilation setup:
Complete Grow Room Ventilation Kit
Here’s a complete list of ventilation system equipment for the above 6×6 grow room.
- 1 x 8″ Exhaust fan : Hurricane Inline Fan 745 CFM
- 1 x 8″ Carbon filter : Vivosun 730 CFM
- 8″ Flexible aluminum ducting + clamps
- 1 x 6″ Intake fan : Hydrofarm Active Air 400 CFM
- Duct reducer 8″ to 6″
This will allow you to hook the 6″ fan with 8″ ducting.
- Duct wye branch 8″ x 8″ x 8″
- 2 x Oscillating fans
- 1 x Dehumidifier
For a complete guide on how to setup a grow room from the beginning, please take a look at this article: ‘Grow Room Setup’.
Grow Room Ventilation Tips
Here are some tips for ventilation system in grow room or tent that might be useful to you:
- Large grow room or tent will heat up more slowly than the small one. The same thing applies to the CO2, which CO2 in a large grow space will tend to last longer than the small one.
- Using an air-cooled reflector on the HID grow light will help in reducing the heat emitted by the light.
- Always place the exhaust system at the top of grow room or tent, considering the hot air moving upwards.
- It will be great if you use an air filter combined with a bug screen on the intake fan. It will prevent pathogens, insects and dust in the air from entering the grow room or tent.
Strictly speaking, setting up a grow room ventilation system is not an easy task. Even some advanced growers have experienced several failures before they finally get a good ventilation system in their indoor grow room or tent.
From that lesson, you know that you must totally understand your indoor garden, whether it’s a grow room, grow tent or grow box. Once you understand it, you can determine which type of ventilation system is best for your garden. And more importantly, you can understand how the ventilation system works in your indoor garden.
We hope this article can help you build or setup the right ventilation system for your indoor garden. Please don’t hesitate to let us know by leaving a comment below if you have any questions or suggestions on this topic. We’ll be very happy to answer your questions and hear your feedback. And lastly, don’t forget to share this article if you enjoyed it and let your friends know. Go Green and Happy Growing!