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How To Build A Grow Room for Cannabis Plants? (Part 2)

Added 4 February 2020

How To Build A Grow Room for Cannabis Plants? (Part 2)

If you’ve missed the first part of this series, this article won’t make sense. Thus, go ahead and read the first part of how to build your own grow room. In the previous part, we discussed important stuff including lighting and space, and we will cover a lot more here.

So, now that you’ve got the lighting down to at, let’s get to the most important part – temperature. 


If your grow room is too hot or too cold, the plants simply won’t grow. You can have the most sophisticated grow room in the world, but it’s all moot if the temperature isn’t moderate. Cannabis plants grow well within a range of 22°C to 31°C. Some autoflowers grow even when the temps dip to 18°C, but the plants begin to struggle if it dips further.

On the other hand, if the temps rise above 32°C, you’ll notice that the leaves look burnt. Also, temperature control is important because you don’t want the grow room to be so hot that it catches fire! Yes, you’ve got water, electricity, and heat in there, and things can go wrong at times. Thus, ensure that you have a solid temperature control system before you finish building your grow room.

Firstly, focus on the air exchange. All the hot air that collects inside the grow room should exit somewhere, and cool air needs to be pushed into the room again. Also, plants consume carbon dioxide and in turn release some moisture. Stale carbon dioxide needs to be sent out while fresh air comes in.

In other words, there must be an inlet for air to come in with an exhaust for the air to exit. If your budget allows you, using a good carbon filter will also allow you to mask all the smell emanating from the room. For growers that fit in too many plants, a carbon filter is a must. It will also work really well if you attach the filter into the exhaust.

Technically, it makes sense to place the air inlet at the bottom of the grow room. This is because air rises as it becomes hot. Some growers punch in holes through the fabric of the grow room. Although this does help to an extent to remove hot air, your grow room will no longer remain discreet. Plus, you’ll have to deal with the light escaping the grow room.

Installing powerful exhaust fans will help to create a good airflow in the room. If you don’t have too many lights, controlling the temperature won’t be an issue but if you have more than 300W lights, creating a good setup for air exchange is critical.

All you need to do is create an environment that makes plants feel like they growing outdoors. This means the temperatures should be the same outdoors and indoors. The faster the fans pull out all the air, the more efficient the cooling will be. Some people try to do this with air conditioners, but it will cost you a bomb because electricity isn’t cheap.

But, how many fans would you need? And how would you calculate it?

It’s pretty simple actually. First off, determine the square footage of your grow room and multiply that with the height. For instance, if you have a 4X6 ft room with 8ft height, then it’s 4X6X8 = 192 cubic ft. Now, you’ll need powerful fans, so go for anything that’s above 700 CFM. CFM or cubic feet per minute refers to the airflow, so the higher the better.

You can also install oscillating fans just to make the plants feel like they are outdoors. Plus, it helps further to cool down the hot air and increase airflow as much as possible


The next important topic is humidity. Cannabis plants grow very well if the humidity is just right. If it’s haywire, a lot of things can go wrong. Also, the ideal range of humidity differs from one stage to another. Basically, you need to consider humidity based on the seedling, vegetative, flowering and late flowering stage.

During the seedling stage, a range from 65 to 70% is recommended. While it can increase to 40 to 70% during the vegetative stage, the flowering stage will be smooth if the levels are around 40 to 50%. Do not ignore the humidity especially during the flowering and late flowering stage and reduce it to 30 to 40%.

You can control humidity easily with a dehumidifier. If the humidity is high, it encourages leaf growth whereas low humidity helps the buds to develop well. You could also use hygrometers to detect the humidity levels.

Setting up the grow room

If you’re keen on using a grow tent, you don’t need to build anything. However, if you want to build the grow room yourself, you will need:

1. Wood for the top, bottom, and side frames. Depending on the size of the grow room, the frames will differ too. All you have to do is construct a rectangular box with 3 sides and the top as the roof. The higher the space, the better. Make sure you provide some sort of support and install vertical beams so that the grow room doesn’t collapse.

2. Use material like blackout canvas or any thick polyester fabric to cover the box completely. Of course, you’ll need to leave some space to open the grow room. For the door or any opening, use Velcro and stitch it along with the fabric with the exact measurements of your grow room for a snug fit. Or, you can use a huge zipper and stitch it too. Ensure that the material is thick enough to prevent light from escaping.

3. Use mylar sheets to cover the inside of the grow room so that the plants use as much light as possible.

4. Use thick plastic to cover the bottom of the room so that the wood doesn’t get wet when you water the plants.

5. Fix all the oscillating fans, lights, dehumidifier and exhaust fans. Attach a carbon filter to the exhaust to suck the smell out. Also, purchase a timer because you’ll need to switch on and switch off the lights depending on the type of plants you’re growing.

6. If there are any holes or gaps in the setup, there will be a lot of light leakage. Use duct tape to cover the holes and use as many strips as possible to make sure the light doesn’t escape.

And, that’s about it! You have created a grow room where you can grow plants.

Safety Tips

Since the grow room is a combination of electricity, water, and heat, you need to be careful. Make sure that there are no loose wires lying around because you can trip and fall. Secure wires with cable tags and keep them out of your way. Secure the lighting equipment properly so that it never comes in contact with water.

Do not leave your grow room unattended for a long time. Check out how the plants are growing every 1-2 days even if you install an automated system. Lastly, bring in the pots along with the soil. Fill the containers outside so that the grow room is clean. Make sure you regularly clean the debris as the plants start growing.

So, now that you have your own swanky grow room, choose your favorite strains and get growing today!



Thanks for the tips!


Great tips! Also +1 on the diagrams.


:smiley: Thank you for another great article.


Some great tips here! Thanks for sharing