Growing your autoflowering cannabis indoors is the best choice if you want to have full control over all the environmental variables as well as be near your plants to check on them and adjust their growing conditions.

Autoflowering plants usually are grown by beginners and are used for personal use so there is no need for large grow rooms and massive light and ventilation systems. And that means a couple of plants in a grow tent or a grow box can be enough to supply your personal needs.

Even if you want to share the harvest with a couple of friends a small autoflower grow room can give you a decent harvest every two to three months and in that way giving you 4 to 6 harvests a year. When you grow your own medicine you will be certain that it is grown organically and will most likely be pleasantly surprised how good a homegrown bud tastes if you compare it with the ones that you can buy on the street or in a dispensary.

After deciding to start growing your own cannabis and choosing the right strains you will have to design your grow room from the ground up or buy a pre-made grow box.

Of course, the easiest way is to buy a pre-made tent or grow box but that is a whole different story and there are many different options available on the market. But because usually, people want to design their own growing environment, so I created this guide so you know what to look for when designing your grow room and what things you need to create a great growing environment.

There are many aspects that go into a grow room and it is not as easy as buying lights and planting your seeds under them so before you start your grow at least consider all the points in this guide.

Grow room size

The size of your grow room is the first thing that you need to consider and that size will depend on factors like:

  • Space constraints: The first thing you have to take into account is how much room you have to build this grow room? Grow closets and boxes come in various sizes starting from a PC grow box to a complete and dedicated grow closet. If you have the room then you can build a built-in closet anywhere in your house but if space is an issue you can transform a mini cupboard or even a mini refrigerator into a great grow box.
  • Budget: Budget also is a big issue because you will not be able to complete a dedicated built-in grow room on a couple of bucks but building a small PC Grow box or a small grow tent won’t cost more than a couple of hundred dollars. If you have the funds you will be able to buy the best materials and equipment but usually, beginners are on a budget and make do with DIY things.
  • Expected yield: And the expected or required amount of dried buds is also a big issue because you will not be able to harvest a dozen ounces from a small closet grow but you can definitely pull out more than 20 ounces of dried buds from a dedicated built-in closet grow with HID lights.
  • Stealth or not so stealth: And the last factor to consider is if you want to create stealth grow environment or unwanted eyes is not an issue. If you want to completely seal all the light leaks and mask the odor then there will be some additional space needed and that will decrease the actual grow area.

When you are designing your grow room you need to consider all these factors and only then start to build your room. Cannabis can grow in almost any environment and autoflowers especially can be very small for small grow boxes but super autoflower strains can grow to heights more than 1 meter and can yield you close to what the photo-period plants will give you.


closet growing lamps with text

When you know what size grow room you will be using for your autoflower grow operation the next step is to consider what light sources and how many lights to get.

There are many options like Fluorescent lights (T5, CFL, PLL), LED lights, or HID (HPS, MH). The good news is that cannabis can grow under all of these lights but depending on your growing conditions you should choose the most suitable grow light for your environment. Here are some tips to get you started:

  • Cost: The most obvious starting point is your budget as that will most likely determine what grow light can you afford and will greatly decrease your search options. If you are on a budget then you can get any regular CFL bulbs from your home depot store and grow cannabis under it but if you have money to spend you can get more expensive grow lights like T5, HID, or even the newest addition and the most technologically advanced LED lights. You should also consider not just the upfront costs of your lights but how much electricity they will use (their efficiency) and they’re lifespan and combining all those measurements you can calculate the most efficient light that you can afford. For example, LED lights are the most expensive but they are also the most efficient and can last up to 50000 hours so if you plan to grow a lot of autoflowers in your grow box then that can be a very good investment into the future. But if you are on a tight budget you can use those, previously mentioned, CFL bulbs that will chew up a bit more electricity but will be with very low up-front costs.
  • Heat: If you are growing you plants all year long then in the summer months heat can become a big issue with some HID light as they produce a lot of excess heat, so be sure to take the heat output into your calculations. Of course, every light source will produce some heat (even LED lights) but the more efficient a light source is the more energy it transforms into light not heat. If you have a small growing area your best bet is to go with fluorescent or LED grow lights but if you plan to get good ventilation and maybe even an air conditioner then you can use any light source you want. And sometimes if you live closer to the poles you will need to heat up your grow room and here those HID lights can come in handy whereas LED light will not give off enough heat to properly heat your grow room.
  • Grow room size: And the last thing to consider is your grow room size and how much light will you need for optimal growth. A good rule of thumb is to get at least 2000 lumens per square foot of growing space. But the optimal range is somewhere between 6500 to 7500 lumens per square foot. That means that you need a lot of light to create optimal growing conditions for your cannabis plants. Every light source has a different efficiency. For example, if you have10 square feet of grow space (around 1 square meter) then you will need at least 65000 lumens of light to get good growth. And depending on the light source that can mean a couple of dozen CFL bulbs, 200 to 300 watts of LED lights or one 400 watt HPS grow light.

Electricity and wiring

Another crucial thing to keep in mind is that you are working with electricity in close proximity to water and putting bulbs in a confined space so you have to be extra careful about your wiring and safety procedures.

If you have a friend that knows how to properly wire a light source and ventilation equipment then it would be best if you could get professionals to help but if you have a very stealth grow operation you should be extra careful not to leave any loose wiring that can create short circuits and start a fire. If you are using heavy lighting equipment you should check if your circuit breakers are able to withstand that load and be sure not to use cables that are too thin as they can heat up with high loads. All electrical components should be installed as high as possible so there is less chance of any water getting on those wires and electrical devices.

Another great thing to do is to keep a fire extinguisher close to your growing area so that if anything bad happens you can quickly step in and fix that hazard.

Ventilation & Heat


After you have installed your lights the next thing you need to think about is the ventilation system that will circulate the air inside your grow box as well as push out the hot air and pull in the cool air that will lower the temperature from those hot grow bulbs.

Air circulation is very important not just to lower the temperature but also to replenish the used up CO2 that plants need to create energy.

  • Air exhaust: The most important thing to install in your grow box is an exhaust ventilation system that will pull or push the Hot air outside of your grow closet. No matter what light sources you would use they will create some additional heat and if that heat is not ventilated out of your growing area then it can build up and damage your plants. Autoflowers usually don’t like temperatures that are higher than 33-35 C and if the temperature inside you grow-box exceeds that threshold your plants will start to wilt and struggle. The exhaust system has to be installed as close to top as possible because the hot air rises to the top and the exhaust system will be more efficient at getting rid of that heat in this way. This exhaust fan should be strong enough to pull all the air inside your grow room out at least once every 60 seconds but preferably once every 30 seconds. That means that you will need to calculate the volume of your grow box and find a fan that can move that amount of air several times a minute (and keep in mind that adding a filter decreases a fan’s performance).
  • Air intake: To pull in cold air from outside the growing environment you need an intake fan or opening depending on what intake system you use. For most grow rooms that are not sealed air-tight it will be enough to just install a more capable exhaust fan that will pull the cool air from the surrounding room. But for larger grow closets and grow tents you will need an active intake fan that will blow cold air inside the grow room and decrease the temperature as well as replenish the CO2. Just be sure to set up this intake fan to be smaller than the exhaust fan so there is a negative pressure forming inside your grow box.
  • Negative pressure: Negative pressure is a low-pressure area where the air density is lower than in the surrounding area and because of that the air will be pushed towards the lower pressure area. When we talk about autoflower grow closets and negative pressure the thing that you need to understand is as soon as you install an exhaust fan it will blow air out of your grow room and create a negative pressure area inside the grow box and air from all the cracks and crannies will flow inwards. This is great for odor control and for air intake because as long as you have a strong enough fan sucking the hot air outside of your grow room there will be enough negative pressure forming that you will not need an intake fan. But if you have a grow room that is almost or completely air-tight then you will need to install this intake fan but keep in mind that it should be smaller and weaker than the exhaust so that this negative pressure will still work to your advantage and will not create any odor leaks.
  • Air Circulation: And the last thing that you need is also an air circulating system inside your grow room. When you are growing cannabis outdoors there are winds and rainstorms that toughen plants but indoors there are no wind and no rainfall so your autoflower plants will be weaker. And at the first glance it does not sound like a problem but when you consider that as the plant grows it will produce dense and heavy flowers then you can understand that these flowers can easily break those weaker stems. And another function that wind does is it replenishes the CO2 that plants use by constantly circulating the air. If you imagine a leaf using up all the CO2 around itself and forming a bubble with fresh oxygen then you can start to appreciate why an air circulation fan is necessary. And you don’t need a massive fan but any old oscillating ventilator will be sufficient!

Reflective materials

reflective materialsWhen you are creating your grow room another thing you need to think about is the reflectivity of your room and reflections are needed to increase the overall efficiency of your grow lights because dark walls and materials usually absorb light but white materials reflect it. That means you can increase the overall light efficiency just by putting reflective materials around your grow room that will direct more light on your cannabis plants. It is said that you can get up to 30% light to your plants with proper reflective materials around your grow room walls and additional grow light reflectors so that means more and faster growth and more yield at harvest time. These are the most common reflective materials:

  • Mylar: One of the best reflective materials you can get as it reflects around 95% of the light that shines upon it and that means more light to your plants. Mylar is cheap and is the most common material growers use for reflecting light!
  • White paint: One of the easiest methods to do is to just paint all the walls and ceiling as well as the floor with white “matte” paint that will reflect around 90% of the light. Just be sure not to buy the glossy paint as it is less reflective!
  • Emergency blanket: Another great and cheap option is to line your grow room walls with emergency blankets that can be bought in drug stores and any home depot. These blankets have around 75% reflectivity because they are very thin and usually growers line the grow room with multiple sheets to get the best result.
  • Black and White Polymer: Black and White Polymer sheets or also known as panda plastic is a great reflective material that can reflect as much as 90% of the light but this sheet can be quite expensive.
  • Aluminum foil: Aluminum foil is the go-to material for many growers but contrary to popular belief it is not that reflective (only around 60%) and all those creases and bends can create hot spots that can burn your plants so use this material only as the last resort.

And another thing you need to consider is your grow light reflector as usually grow light bulbs (except LED lights) are creating light in all directions and that is inefficient so a reflector can direct all that light toward your plants. You can increase your lamp’s efficiency by as much as 50% by just getting a proper reflector and that obviously means more growth and bigger yield from the same light with little up-front costs.

Measurements & data

When most of your grow room is done and you will start your growing you will also need to keep track of all those environmental conditions and that means installing various devices like low and high thermometer and hygrometer so you can keep track of the temperature range during the day and night.

You would also need a light meter, humidity meter, and a PH meter to get the most accurate data about the growing conditions and act according to that collected data. The more data you collect the better will be your judgment on what is going on with your plants and if something is going wrong then you could act accordingly but if you have no data then you can just guess what could be the problem and often misread your plant and do more harm than good.

There are many different measurement devices but for complete beginners, it will be enough to get just the thermometer and hygrometer to measure the temperature and the humidity because all those other measurement devices will need specific knowledge so you could understand what are you looking at.

Growing method

Before you start germinating your seeds you should start researching various growing methods as there are many ways to grow cannabis starting from a simple soil growing to some advanced soilless mixes that require more precise nutrient solutions and even some hydroponic and aeroponic systems that require pumps, nutrient solution tanks and some specific knowledge to get started.

If you are just starting out the best way to learn is starting with regular organic soil that has a correct PH and maybe even some small amounts of nutrients that will let your plants have a great start in their life. But if you will be using hydroponics or aeroponics you will need more room and more equipment that will use more space so keep that in mind when constructing your grow environment.

Water barrier – When you are planning what growing method to use be sure to keep in mind that you have to create a so-called water barrier where under one concrete horizontal line you won’t install any electrical appliances as there is a possibility of water spilling and creating short circuits. It is best to place all the electrical components as high as possible so there is no fire hazards.

Stealth growing



Autoflowering plants usually are grown by newcomers and people who want to grow cannabis but do it stealthy and without anyone knowing what they are doing. This is why you should also consider some aspects of stealth growing like odor control, light leaks and sound leaks that can be a huge sign for any strangers that something fishy is going on in hour house.

  • Odor control: The first thing that can give away the fact that you are growing cannabis is the smell of your flowering plants as marijuana usually produce a distinct odor that can be instantly recognized. That is why you need to install a carbon filter or an ozone generator that will get rid of that cannabis smell. Of course, all these methods are not 100% efficient and you can add some more electrical deodorants that spew out a great perfume every now and then to mask all that growing cannabis smell.
  • Light leaks: The next thing that you need to keep in mind is that your grow box will most likely create some light leaks that will be noticeable if you have visitors. But if you want to create a box that is 100% light-proof you will have to do some clever engineering as you will need materials that are light proof and also the grow closet doors will have to be sealed so no light can escape. But usually, light leaks are not that big of a problem because inviting friends to your room where you are growing auto-flowers is not a great plan in the first place.
  • Sound: If light leaks and odor can be masked and dealt with then the sound of your fans blowing air is the hardest to mask because there is just nothing you can do to decrease the sound of those fan blades. Of course, you can get the quietest fan but it will still create some sound vibrations and the only thing that you can do is to get an adjustable voltage fan speed controller and turn your fan to the lowest possible setting that won’t overheat your plants. Of course, you need to install your fan with great insulation and you can put it in the farthest corner of your room but you will still hear that humming sound.
  • Heat: If you are using huge HPS lights then they can emit a lot of excess heat and the room where your autoflower grow box is located can get quite hot. Of course, you can tell your guests that you like warmth and that is why you use electric heating and that is why that excess heat should not be that big of a problem for stealth growing.

Advanced Grow room elements

And then there are some advanced grow room elements that usually are used by experienced growers that can be considered experts and that want to maximize their yield as much as possible from the same energy usage.

These methods usually are not feasible for beginners and they can get quite expensive and you really need to know what you are doing before you start to use them.

  • CO2 enrichment – One of the more advanced growing methods that is used by a lot of experts is CO2 enrichment that basically means adding additional carbon dioxide in your grow room to promote more growth from the same lights. Plants use carbon dioxide to create sugars in that photosynthesis process and the more CO2 the better. But if you want to add additional CO2 then you need a pressurized carbon canister and a mechanism that will automatically enrich your grow room with that CO2 a couple of times every hour. Some growers say that with this method you can get up to 30% more yield but I think you should start thinking about CO2 only when you have maximized your grow room and mastered the art of growing.
  • UVB radiation – When cannabis plants are growing outdoors they get the full spectrum light from the sun and that also includes the natural UV and UVB radiation that is usually harmful to humans but with cannabis, it could be in fact beneficial to them. The thinking goes that UVB radiation promotes more THC production because your autoflower plant wants to protect its seeds from these harmful rays and by suppling small amounts of UV radiation to your autoflowers you can get better THC concentration and frostier buds. Some experienced growers say that you can get much more resin on your buds but those UVB bulbs are quite expensive and they are also dangerous to humans so it is best to start experimenting with them only if you are an expert and know what you are doing!

And so we have reached the end of his Autoflower grow box guide. I hope it will be a great start for any beginner because here are all the main points that you need to consider when planning and designing your grow closet or an autoflower grow tent!


  1. Moondude on

    Has anyone used “The Exhale” homegrown CO2? In a bag that you open and leave in tent.

    I have a friend that told me not to do this. Any input?

    Thanks Fellas,


    • I havent used those CO2 bags myself but have heard some polarizing reviews where some say that they work great for autoflowers but others say that they don’t work at all.
      I would also be interested to hear some real life reviews.

  2. Arron Lopez on

    I’ve used the co2bags n so far no issues and can’t seem to see if it works since I’m still new to this and after a few grows I’ll know more but try the surgery and yeast method it’s cheaper

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