Part 1: Environment

Our latest publications on actionable growth advice for the home grower.

Temperature and Humidity

Grow room setup is the least talked about subject in home growing, and maybe the most important. A properly designed room can be the difference between being able to produce ample amounts of exceptional Cannabis, and dismal returns of inferior flowers.

Lights produce a lot of heat, and plants transpire a lot of water! We need to deal with these issues so our plants can thrive, and reach their full potential.

At Back Room Grow you have an advantage.

We will help guide you through the expansive, rapidly changing, and often confusing world of cannabis growing. When you start to calculate how much wattage is needed to produce in your space. Please remember when done properly we can get you growing WAY MORE Cannabis! By investing in the right equipment the first time around, you can grow the same amount as those using outdated technologies yet at a fraction the amount of money.

When Building a room there are a few key points that go a long way when it comes to maintaining your gardens environment. We need to, Insulate, Vapour Barrier, Light Proof, and seal the room off so we can control air movement both in and out of the room. The more insulation your garden has the easier it will be to control the temperature inside the space regardless of the conditions outside of the garden. This can be a make or break difference during the depths of the frigid winter, or blistering summer weather some may encounter.

If in a room, we need to seal the room off so we can control air movement in the room. A drywalled room is a good start, using a green wall is even better. Without a hard surface, this it is very difficult to seal. If the walls are properly taped, no cracks or holes, we can then seal around the baseboards. Run a line of latex causing above and below the baseboards effectively sealing the wall to the floor (concrete is great here).

Even better though is sealing the room with vapor barrier. You can line the interior of your room with “Panda film”, or black and white poly. This provides some reflective benefits, anti fungal properties and can be used as a vapor barrier.

Windows should be completely covered, plywood and caulking. Close all heating vents and seal with thick plastic (Panda film). You may have to affix (drywall screws work) and then seal around edges.

Doors need to be tight fitting, with weather stripping to seal and a “wipe”at the bottom. Basically anywhere air can come in we need to seal it up. Now we can control our grow room environment and move air around effectively.

Our home needs some environmental help!, moisture removal is first. A dehumidifier is really important for our plant and home health. Plants are going to thrive in your flower cycle at a humidity of around 50% or less. Our home in the winter, depending on window efficiencies, may require a humidity of less than 40% to prevent harmful molds from forming. These molds can be harmful to humans and your plants.

The most common failure of a grow room is inadequate de-humidification!

A traditional residential dehumidifier can work here, they are less expensive than commercial units, but also much less efficient and won’t last as long. For bigger operations a commercial unit or ones designed for professional growers maybe required. These can be expensive but protecting your home and having happy plants is really a must. A rule of thumb with de-humidification is for every gallon you water there is 0.8 gallons that need to be removed.

You can get professional advice here but always remember that too small, it will be overworked and likely fail at the worst possible time. Over size a little and the unit can have a better cycle with cool down periods, prolonging the units life.

Now we have to cool our grow space. Plants really like temperatures below 80 Deg F (27 deg C) with lights and dehumidifiers creating heat. So we need to cool, but by how much and with what equipment?

This the most complicated part of setting up a grow, how to cool a home. Number of lights, size of de-humidification and even the number of people in your home affect this. So what you need to ask first is (if you have central air), can I keep my home cool on a hot July night. If you can, and your garden is on the small size (4 plants or less) you might be able to use your central air to cool your garden, but consider the costs of more cooling if this doesn’t work. In larger grows we need to bring a lot of cool fresh air into our grow from our home. We discuss fans and air intake below

If you need more cooling, to find out how much you can talk to a HVAC (air conditioning) professional, they can calculate home much cooling is required for your set up. They can calculate the heat produced by your lights, dehumidifier and the people in you room.

A good rule of thumb though is you need 400 BTU’s of cooling for every 1000 watts of lights in a good sealed room.

Deciding on what type of air conditioner is really important. A in room air conditioner, or portable, won’t work, unless it has hoses that you can duct out of the room These units put out as much heat as they do cooling in your home, cool one area, heat another.

Any air conditioner for this purpose must send the warm air outside. A window unit can work (we worry about mold on the unit and smell going outside), a portable air conditioner, with hoses to get rid of warm air, is also a possibility.

The best way to cool a room is with a mini split air conditioner. These have the cooling unit outside, and a room specific heat exchanger in your grow room. So we can set temperature in our room and control that separately from the rest of the home.

ventilation for indoor cannabis growing

Mini splits are more expensive than other units but really provide the best answer for cooling a grow room in a home. You can even get mini splits with more than one indoor unit so you can cool different rooms to different temperatures. My room stays at 77 deg F(25 deg C) and my home is 70 deg F (21).

Some basics of cooling:

Every watt of electric used no matter what for produces that same amount of heat in the room. All electricity utilized eventually produces heat. You can see the math here (hyperlink to science page). So we need to take into account all lights (yup led’s follow the same law) dehumidifiers, fans etc. Anything that uses electricity we need to have cooling.

Air Movement

Now that we have the right temperature and humidity for our room we need to make sure we get fresh air in our room and move it around really well.

If in a tent the ports for ducting are already there and set up is fairly straight forward, please follow manufacturer’s instructions, but generally we want air intake near bottom of tent and the extraction ducting at the top The cool air is both CO2 rich and heavier. This is slightly inefficient, as cool air sinks, but is the best for keeping cool air flowing through the plants.

Cannabis plants like all living things require a lot of carbon to grow. Cannabis gets its carbon through respiration of carbon dioxide. So to keep fresh carbon dioxide coming in a room we need to keep fresh air coming in. So we need ducting, a fan and a filter.

We can add extra carbon dioxide to a room, but the room must be sealed and we have to change some of our processes, how we run things. If you think you want to generate carbon dioxide you can see if here.

The size of the filter is calculated by this, We want to bring in air from another room. Set up looks somewhat like this.

The fan is actually sucking air out of the room, through the filter (keeping plant smell out of the rest of your home) and drawing fresh, cool air in. This brings fresh source of carbon to your room, but now we have to make sure we get that carbon dioxide to the plants.

Here we install fans, whether in a tent or room, we need to move the air around the space, and over our plants. Fans provide two functions, removing heat from between your plant canopy and light and bringing fresh carbon dioxide into the room. The fans also “mix” the air meaning that the cold fresh air is mixing over our plants and not just “passing” straight through the room.

In a room where there is more space than a tent, we can have the cool fresh air come to the top of the room. Cool air falls so we want to have it come through a duct just below the ceiling of you room. We can then place a fan near that where air exits the duct. This will effectively mix the air so that the cool air just doesn’t drop to the floor.

The air exit (where the filter is) should also be at the top of the room and as far away (opposite side of room) from where the air is entering the room.

Now we have fresh, carbon rich air coming to our plants, feeding and cooling them.

Electrical and Plumbing

Electrical hook ups, lights, pumps, fans etc. should always be installed by a professional or a competent home owner. Mixing a wet environment with a lot electrical devices is well lets say it, DANGEROUS.

Please make sure all outlets are grounded properly, GFI receptacles or better (some equipment cannot run off a GFI circuit) . If you don’t understand that last statement then you really need a professional. My room was wired by a professional and it means that is one thing I don’t have to worry about.

Read about the lighting advantages of properly utilizing “every other phase” when using 220v power.

For plumbing things still must be done to high standards, but you are less likely to harm yourself. We talk more about the plumbing requirements in the Coco Hydro set up page, but generally you want to keep standing water out of your room, anything that adds more humidity. Nutrient make up tanks and water tanks should be outside your grow room, this also helps keep the liquids cool, which we need for our plants.

Also keep in mind you are likely to overflow some water at some point, it happens. you need to think about is going to happen to that water, protect your home. A simple pond liner covering the floor and running a couple of inches up the wall, even at the entry door, can act like a bathtub and hold that spilt water. When it happens and it will you will be so happy you thought about this first. I didn’t, but I learned.

I know that there is a hesitation to bring outside individuals into your grow room. I understand this and have gone through it. You want good people but want your privacy.

So here is what I did and it worked for me. I didn’t know any trades people in the areas I needed and frankly I was hesitant in the beginning to bring in anyone I knew. Was afraid of social chatter. I found some trades people, that were not the well know but more like the small entrepreneur. They all had some experience in this area, were discrete and knew what I was looking for.

Like with gardening “everything is timing”, it is best to seek out these tradespeople before you have an issue and are forced to start chatting up the grow store staff. Check them out online, look for referrals and if doing a project, contact them a couple of months in advance. I have done it the other way, needing to get something done quickly, and I paid dearly for that urgency.

Hope you can find your own tradesperson “hero”, I have found a few.

If you follow these basic principals your room will be set up and allow for successful growing.

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