Cannabis can be grown just about anywhere, including indoors in small spaces. However, there are some difficulties you might run into when growing inside if you don’t have the right environment controls in place. Cannabis needs to stay within a certain humidity and temperature range to be healthy, and lights and regular watering can make that hard indoors.
Setting up a successful small indoor grow takes some planning, but it’s not hard. Here’s how to set up your cannabis grow environment for a healthy, happy crop.
Cannabis Environment Overview
Cannabis evolved to fit certain conditions, and it grows best when you replicate them. Ideally, you should keep your indoor grow at the same temperature and humidity levels cannabis enjoys in the wild. The easiest way to do that is through a well-designed ventilation system.
Ventilation systems also have some other benefits, like minimizing the smell of your crop and preventing mold from growing in your garden. Even the most basic grow can benefit from having a basic ventilation system.
The first and most important aspect that a ventilation system will control is your grow’s temperature. Just because cannabis plants like it warm doesn’t mean they like it too warm. Cannabis plants grow best when temperatures are kept between 68-78 degrees Fahrenheit. If you’re comfortable, so are your plants.
The problem is that cannabis plants need a lot of light to grow to their full potential, and most grow lights are warm. Even LED lights produce some heat, despite how efficient they are. This heat builds up in an enclosed space, and before you know it, your cannabis plants are wilting in a 90-degree sauna. A good ventilation system prevents this by blowing hot air out of the room and pulling good, cool air in.
Humidity is another common problem that growers face. Outdoors, excess water is part of the water cycle – it evaporates away and turns into clouds that get blown away. Indoors, however, the water evaporates and just hangs out. It has nowhere to go. While you do want some humidity, too much is bad. Cannabis thrives in humidity levels between 40-50%. That’s about where humans are comfortable, too.
Excess humidity encourages mildew and mold, as well as all sorts of other pests. Moldy buds must be thrown away, because smoking them can poison you. Keeping your humidity in check can save your crop.
Ventilation systems take care of this problem the same way that they take care of excess heat. The air that your ventilation system removes is the wet air from inside the grow room. It then pulls in fresh, dryer air from outside the room, lowering the overall humidity.
There are two other major problems that ventilation systems control. First, your plants benefit from having some air movement in the room. Spider mites and other tiny pests prefer environments where everything stays still. Having just enough airflow that your plants’ leaves rustle helps keep mites from making themselves at home.
Second, the distinctive smell of cannabis can build up over time. By keeping your ventilation system running, you can vent the smell out before it builds up to noticeable levels. This helps avoid annoying neighbors and roommates.
How to Install Vents
The most basic type of ventilation system has four parts: an intake vent, an outflow vent, a thermometer/humidity reader, and a fan. The fan is usually attached to the outflow vent, pushing air out of the room. The intake vent should be far away from the outflow vent, so that the air coming in is fresh. The intake vent doesn’t need a fan; it passively allows fresh air to replace the old air.
Many grow tents come with vents already prepared. In this case, you just need to place a fan next to the outflow vent, plug it in, and turn it on. However, if you’re using a closet or small room, then you may need to install vents yourself.
Despite what you might think, windows are not the best place to install an intake vent. Windows are perfect for outflow – the heat and humidity leave your building entirely, and they are no longer your problem. If you have windows, save them for the outflow vent.
Outflow vents should go outside if at all possible. If that’s not possible, you can also consider connecting to your building’s normal ducts. In particular, connecting your outflow fan to a laundry room vent is useful. Steam and warm wet air are expected to come from a dryer vent, after all. This will likely require installing ductwork, though, which takes your grow to the next level.
The actual ideal place for an intake is the door. Plenty of doors come with grates built into the bottom. The simplest way to install an intake for a room that doesn’t already have one is by changing the door to one with that vent along the bottom. This is especially true because your intake vent should be three or four times larger than the exhaust fan, so you don’t wear out the fan too quickly.
If changing the door isn’t an option, it’s time to consider using ducting in your grow.
How to Install Ducts
Ducts are the next step in creating a great indoor grow ventilation system. Some simple ductwork can help you pull in clean air and vent old air wherever you want. It’s not the stealthiest option, but if done right it’s not hard.
The first duct that should be added to any grow is one that connects directly from your light’s exhaust fan to the outflow vent. Since ventilation is primarily about heat, connecting the heat source directly to the outflow vent is efficient. If you regularly raise and lower your lights for different grows, get flexible tube ducting and leave some slack. You can gather this slack together with binder clips when it isn’t needed. You just need to have enough available to connect the light and the exhaust vent when they are as far apart as they will go.
Adding ductwork to the exhaust equation gives you more options. If you’re growing in a room without a window, for example, you can use ductwork to send the old air out the window in another room. A small grow doesn’t require wide ducting, so you can route it under furniture until it gets where you want it.
The next ducting you might add is some intake ductwork. Getting to a clean air source might be a little tricky, depending on where you’re growing. Again, you can use ducting to connect to a guaranteed clean air source. If you add an intake fan, the intake vent can be the same size as the exhaust fan. That means you can connect the intake fan by ducting to any AC grate or another air source in the room to guarantee clean air.
When installing ducting, use tape intended for ductwork – real duct tape. This helps keep your ducts air-tight. If your ductwork leaks, it’s not as efficient, and you’ll start running into temperature and humidity problems.
Set Up Filters
After you’ve made the step to ductwork, you should strongly consider adding filters. A carbon filter is a great way to minimize the scent of your crop. Cannabis has a potent scent, and there are plenty of smokers out there who don’t want to smell it all the time.
You can find carbon filters online or in many large hardware stores. These filters should be placed just before the exhaust fan. The point is to force as much air through the filter as possible before it makes its way outside.
You’ll need to change carbon filters regularly. After a while, the carbon will reach the limit of what it can absorb, and smells will start escaping. Remember to always read the instructions for how long your filter lasts, and be sure to change it regularly.
Cannabis Humidity Controls
If your ventilation system isn’t removing enough humidity, then you should consider adding specific cannabis humidity controls. A good dehumidifier can be your friend. When looking for a dehumidifier, look for one that allows you to set the humidity level, as you don’t want to go from one extreme to the other.
You should also look for humidifiers that can remove enough water. A small grow room should be fine with a capacity of 15-20 pints. The rule of thumb is that the amount you water your plants a day should be the same amount your dehumidifier can handle.
Rarely, a climate will be dry enough that you’ll run into low humidity in your grow room. In that case, you can usually fix the problem by leaving a bucket of water underneath your lights next to the plants. The heat of the light will evaporate water and raise the general humidity level in your room.
Ventilation can help keep your plants happy and healthy, even in small grow rooms. It isn’t complicated to install – if you can put Ikea furniture together, you’re overqualified. You can install ventilation into any space, as long as you understand how it works.