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Indoor marijuana growing has many pros: Your plants are always safe, you control their environment, and you can customize your crop as you see fit. However, this convenience requires a little bit of initial effort and planning, as you will need to build an indoor grow room for your plants. Although it might seem hard at first, many options can make your life easier. With this detailed guide, we want to help you have a seamless experience and realize that grow room building is fun (and easier than you thought)!

Planning and Calculating

Before you start building a grow room, you must be able to know what you want to get from it. To be more precise, you need to know:

  • How many plants you want
  • How much time you have available
  • How good you are with a set of tools
  • Your budget

Luckily, you don’t have to be a pro handyman to build a good grow room. The wide assortment of tools and components at your disposal will make your life easier. However, since this is a beginner tutorial, we’ll be preparing a grow room assuming you don’t know anything about building. You don’t have to be an expert to build a beautiful grow room, as long as you have patience and perseverance.

Find A Suitable Location For Your Indoor Grow Room

The obvious first step of your planning should be to decide where you’ll set up your grow room. This can be anywhere, as long as:

  • There is an electrical outlet nearby
  • The floor has no carpets (wood and tile floors are the best)
  • There is space for fans, vents, and other components
  • A water supply is within a reasonable distance

Unused attics, garages, basements or even spacious cupboards are prime areas for your grow area. Any enclosed room that has an entry point and is sealable will work like a charm. Make sure that you and only you have access to the grow room. No one else must know about it, even if you live in legal states. Also, you want the location to be entirely under your control so that you can control the environment (like a little god of sorts). Nothing goes in or out without you knowing.

Cellars and basements are best because temperature control is easier underground. If no alternatives are available, you may want to consider getting a grow box, or a grow tent to place your plants and grow lights. Many offers frequently run on Amazon and other online retailers, so you won’t have a hard time finding a reliable unit.

Grow boxes and tents are self-contained mini-rooms, designed explicitly for indoor vegetable growing. They are internally coated with a reflective material for better light distribution and usually come with all the necessary components for your first few grows. If you don’t have the time or the patience to build a grow room from scratch, take a look at some of the best cannabis grow kits for beginner growers.

Dimensions

Measure everything before you start building your grow room. Scale the room on paper and write down where the lights, exhausts and electrical supplies will go. Make some room for the entrance and always leave some wiggle room for yourself. Mapping everything out will save you a ton of time in the long run, as you’ll avoid easily preventable mistakes. It’s simple, it’s practical, and it’s fun!

When calculating the dimensions of your grow area, keep in mind that your plants will double in size as they develop from the vegetative to the flowering stage. Therefore, the roof of your grow room should be high enough to accommodate the grow lights, the plants, and your head.

Clean Up!

I hate to sound like your mom, but you must thoroughly clean up your room before turning it into a marijuana nursery. And by cleaning, I don’t only mean sweeping, mopping, vacuuming or sterilizing. Remove any unnecessary junk from the area, as well as any carpeting or fabrics that tend to accumulate dust and attract mold and pests. Then you should sterilize the area thoroughly to remove all possible sources of infection.

Also, it goes without saying that pets and marijuana don’t mix. Their curiosity might get your plants in trouble, as bacteria can infect them and kill your crop in an instant. I know from personal experience that cats go crazy over marijuana plants, so try to keep their fuzzy paws away from your grow area. They will nibble on those plants without a second thought! 

Pick a Growing Medium

This an essential choice you must make before operating your grow room. Your plants must grow on something, and there are a lot of options for the aspiring horticulturist.

Soil

Cannabis Grow Soil

Soil is a tried and tested method when it comes to growing (after all, people have been using it for thousands of years). Special potting soil mixes are super easy to find in garden stores. Overall, soil offers more autonomy regarding nutrients, as it is usually packed with them. On the downside, you need to be more careful with watering, especially at the earlier stages of plant development.

Soil-less/Hydroponic

Cannabis Grow Hydroponics

Soil-less mediums like coco-coir, rock wool, expanded clay, etc., are lighter and give the plant more breathing space; however, they hold no nutrients, like soil.  There are many types of hydroponic systems available to the casual grower. The most popular are:

  • Deep water Culture (DWC) / Recirculating Direct Water Culture (RDWC)
  • Bubbleponics hydroponic system
  • Continuous Flow / Top Feed Systems
  • Nutrient Film Technique (NFT)
  • Drip irrigation hydroponics
  • Ebb and Flow hydroponics
  • Wick

In soilless mediums, you must supply your plants with liquid nutrients and manually add them to the water in which the plants’ roots are submerged. Soilless mediums are more expensive than soil-based mediums, but they offer a cleaner experience and higher quality buds. However, growing with a hydroponic system will take some getting used to. If that’s your first grow and you don’t plan on growing a lot of plants, go for a soil garden and when you feel more confident, move on to more advanced techniques!

Equipping the Grow Room

So, the first step is complete! You have decided where you want to build your first grow room, you have the blueprints, and you know all the details. Everything is ready for the hard part: the actual building of the grow room. Now that the very basics are all covered, it is time to get your hands dirty!

Light-proofing the Room

The first step you should take is to ensure that your growing room is light-proof. In previous articles, we have stated the importance of light in the course of marijuana life cycles. When you are growing marijuana indoors, you are essentially simulating the actual sunlight that your plant expects to receive at any given season.

At the start of marijuana life, the sunlight cycle should be much longer than the dark cycle. As the seasons go by and sunlight naturally decreases, the plant realizes that winter is coming, and focuses its energy solely on flower production. This is why the flowering period needs at least 12 hours of uninterrupted darkness and why flowering will never come if you don’t change the light cycle. When you are in the flowering period, it is crucial that no natural light is allowed in your grow room.

The reason for this is that light leaks during the dark period can mess up your plants badly and reduce yields or lead to the development of male plants (that can devastate your whole crop, by pollinating the females). Even the slightest amount of light can confuse your plants, as their natural tendency is to stretch out to light. Indoor varieties are even more prone to these fluctuations, as they are far more sensitive to stimuli.

Light Reflectivity

Equal light distribution throughout your plants is important, as your goal should be to get as much light as possible directed to them. This can be especially tricky for the areas underneath the canopy. It is, therefore, necessary to use all the available light that would otherwise get “lost” in the process. Covering your grow room walls with reflective material ensures that no plant stays in the dark and can increase the amount of usable light by at least 30%.

If you are looking for the easy way out, grow boxes and grow tents come internally coated in reflective material. If you are the DIY type, there is a wide variety of materials available on the market.

Mylar

Arguably, the most popular choice among growers. It comes mainly in two sizes (1mm and 2mm in thickness). Although it is potentially more reflective than foylon, it is also harder to clean. Its reflection levels are about 92-97% for light and 85% for heat. If you go for mylar, try to use the 2mm version, as it is more difficult to wrinkle.

Foylon

It is made of spun polyester fabric and reinforced with foil laminate. Although it is costlier than mylar, it makes up for its cost, by being more durable and easily maintained in the long run. It reflects nearly 95% of light and about 90% of heat energy. So, before you go further, make sure that your ventilation system works perfectly!

Matte white paint

Cheap, effective and readily available! Flat white paint can be an excellent option if you plan to turn a whole area into a permanent indoor setup. It is also a great option for warmer rooms as it absorbs a lot of heat while reflecting almost 80% of the light energy.

Panda plastic

Panda plastic is a great short-term solution that can also be easily cleaned. It is called “panda” plastic because of its color pattern (white on one side, black on the other). The premise is that the white side is used to reflect light and the black one to trap it during your dark cycles. However, you have to keep it at a reasonable distance from your grow lights because it can melt if it gets too hot. Its reflectivity is about 80%. Opt for the 6mm version for best results.

Orca Grow Films

Orca grow films are pretty similar to panda plastic regarding design, hence the name (orcas are famously the second most popular black and white animal). However, Orca Grow films are more expensive, thicker, easier to clean and mold resistant. All these features make it shine –literally- among its lesser counterpart. It uses a sophisticated crystalline reflective system that distributes light evenly at about 90-95% reflectivity.

How to adequately cover your walls with reflective material

  • The material must stay flat. Wrinkles and creases disrupt the reflection of light;
  • Try to soften the edges and try to avoid sharp angles as they tend to hold light;
  • Keep your reflective material absolutely clean;
  • Try to spread your reflective material on something smooth, if your wall is somewhat rough, try to use Velcro on it first and then proceed.

Eliminate Smells

Your house smells. The only reason you don’t realize it is because you are used to the way it smells. Well, guess what: Your marijuana plants smell too, and you can get used to their stench. So much that you might not realize it until a friend or -worse- a neighbor points it out.

Especially during the flowering period, marijuana plants produce a stench so overpowering that can become bothersome. If you care at all about stealth, investing in an odor control system should be a priority. The cheap and easy solution is to get a deodorizer gel for your grow room. However, the best solution is to fit a carbon filter in your exhaust fan so that the stinky air gets cleaned up before exiting the grow room.

Ventilation

Ventilation is essential for a successful grow room, as it ensures the constant circulation of fresh air in and out of your grow room. To ensure proper airflow within your grow room, you need some oscillating fans to circulate the air within the grow room and overhead exhaust ducts to guide warm air outside.

The trick is to place the exhaust fan at the top of the room so that it can suck away as much warm air as possible. Make sure that your input fans are smaller than the exhaust vent. Many growers find that pointing your oscillating input fans towards the grow lights helps with temperature issues. Using horizontal airflow fans can help even further with temperature and humidity levels.

Useful tip:

A good rule of thumb for measuring your ventilation needs is to keep in mind that 450CFM (Cubic Feet per Minute) of ventilation is good for a 1000W HID lighting setup and about 3/4ths of the air intake. For the first couple of lights a grow room fan will suffice, but if you plan on larger crops, you might want to take things more seriously.

Controlling the Humidity

Humidity is one of the factors that determine how fast your plant metabolizes nutrients. Too low humidity levels can block the proper nutrient intake, while on the other hand, abnormally high levels can lead to mold and pest problems. The thing is, your plants need different humidity levels according to their growth phase and if you manage to do it correctly, you will be rewarded with better yields.

Manipulating the humidity levels in larger grow rooms might be a challenge, but an air humidifier is a wise -and cheap- investment for your grow room, as long as you take good care of it and clean it frequently. Also, they come with in-built hygrometers that can measure the humidity levels of the environment.

Temperature

Optimal grow room temperatures should ideally hover around 72-80ºF (20-25ºC) at all times. Any fluctuations should always be within that scale, always depending on the growth stage. The tricky part is to balance the temperature by taking factors as the heat emitted by lights, heat trapped by insulation, and air circulation into account. Getting to the sweet spot is pretty much trial and error but it is not difficult to get there nonetheless. It goes without saying that a thermometer is one of the essential gadgets of the aspiring grower.

Always remember that grow lights cause most of the heat and their proper placement is essential. You will need about 3750BTUs of air conditioning power per 1000W of lighting in a properly insulated grow room. This rating is taking into account other sources of heat too, like CO2 generators or ballast heat. If you can afford it, go for a powerful, quality A/C unit that is capable of operating at a much higher setting than the one you are after. In such cases, it is better to be safe than sorry. Besides, there is a huge selection of A/C units that you can choose from and some market research could pay off.

Necessary Appliances and Gadgets

Growing marijuana indoors demands a lot of attention to detail and careful calculations. Thankfully, nowadays we are presented with a wealth of possible choices to help us automate the most menial tasks that are involved in the process. So, be sure to add all of these electronics to your shopping list. They can (and will) save you from a world of trouble.

Shopping List

  • Cooling thermostat;
  • Lighting control relay and timer;
  • High temperature shut down;
  • Reliable max/min temp and relative humidity monitor;
  • Humidity controller;
  • Night/day temperature control;
  • Carbon dioxide monitor & control;
  • Extension Cords (always useful).

These little gadgets might seem insignificant at first but will become your best friends when it comes to the actual growing part. The cost might seem daunting at first, but –hey- nobody said it is going to be easy or cheap!

But wait, there’s more. On the next page we will show you a step by step guide!

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