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Building Your own Cannabis Grow Room

So, you have decided to grow your own cannabis at home. Nice one! Growing your own cannabis not only guarantees a continuous supply of wonderful weed, it also leads to a greater appreciation of the herb and the sense of a job well done. It is well documented that time in the garden is as beneficial as meditating, increasing one’s sense of well-being and even helping combat anxiety and depression.

Growing cannabis at home means having somewhere dedicated to growing. To produce enough weed to last from harvest to harvest, a minimum of 1m² is recommended. This will accommodate a number of smaller plants or one or two well-trained, or even scrogged, larger plants. All this is up to you; the yields in the end are similar, it just depends on whether you want a lot of variety with smaller yields per plant, or less variety and larger yields per plant. It is entirely up to the individual.

The height of the grow room is dictated by available space and lights being used. A single square metre is easily covered by most styles of grow light. Less height is required when using fluorescents, as lights can be kept closer to plants throughout the grow, whereas HID lights need more distance to avoid light burn and excessive heat buildup. You might want to blast your babies with a 1000W HID, but without appropriate height, this just isn’t possible.

SELECTING A SPACE

Everyone can find an easily accessible spare square metre somewhere in their home or apartment. Spare rooms, attics, basements, cupboards, and walk-in robes can be used to set up a grow space. Discretion is a key factor; fan noise, light buzz, and odour control each need to be considered when selecting a space to set up a grow room. An oscillating fan attached to a shared partition wall, for example, will drive your neighbours crazy with the noise and sympathetic vibrations.

  • 1. Light proofing
  • 2. Airtightness
  • 3. Air movement
  • 4. Air exchange
  • 5. Climate control
  • 6. The build
  • 7. Collection rack
  • 1. Light proofing
  • 2. Airtightness
  • 3. Air movement
  • 4. Air exchange
  • 5. Climate control
  • 6. The build
  • 7. Collection rack

LIGHT PROOFING

An entirely light-proof grow room is absolutely necessary. In the first instance, light leakage can be annoying because grow lights are extremely bright. Light leakage can keep you awake at night if your grow room is a bedroom cupboard or set up in a spare corner of any inhabited room. At worst, it will advertise that you are growing weed to your whole neighbourhood.

Secondly, light leakage into the grow room can adversely affect plant performance. Once plants have been flipped to the 12-12 day/night cycle to induce flowering, light leakage can confuse plants and lead to a lower yield, hermaphroditism, or even failed crops due to light stress. All growers keep a keen eye out for male plants, but missing a few well-hidden bananas on females can ruin a whole crop by sending it into seed production.

Once your grow space is set up, do a test by turning on the lights and inspecting for any light leakage. Any cracks or holes that let light out will certainly let light in. When and if discovered, patch the holes with light-proof tape available at hardware stores or with at least two layers of gaffer tape—gaffer tape is semi-translucent, even the black stuff, so just one layer won’t do the job.

Most electrical equipment kept in a grow room, such as dehumidifiers, have quite bright micro-LED lights, which can do the same plant damage as environmental light leakage. Place a piece of tape over any lights on these types of appliances to ensure nights are the darkest of dark. Outdoors, the subdued light of the full moon has beneficial effects on plant growth, but this effect is difficult to translate to an indoor grow.

AIRTIGHTNESS

As it matures into resinous, fat buds, good cannabis smells—it’s as simple as that. Some weed even overpoweringly reeks and can stink out a whole room, a whole house, or even a street. It is easy to become used to that luscious aroma when visiting your plants often, and become convinced that the smell isn’t going further than your grow room—but nothing is further from the truth. A well-sealed grow room prevents aromas from disturbing neighbours or your fellow inhabitants.

A well-sealed grow room also makes climate control easier to maintain. Temperature control and dehumidifying/humidifying air rely on a sealed environment without any drafts. A stable environment is very important for optimum plant performance. A well-sealed room also acts as a quarantine cell for your plants, preventing any bugs, vermin, or airborne pathogens from entering. A single mouse can do a lot of damage to cannabis in only one night, especially to young plants, as they are voracious for nutrient-dense cotyledons and young stalks.

It should be noted that an airtight grow room is a low-budget solution. Spending more to set up an air exchange system will benefit your weed substantially and will pay itself back in the long run. However, airtight grow rooms are the ideal environments for experimenting with CO₂ enrichment for added plant performance.

AIR MOVEMENT

Healthy cannabis requires moving air. Any grow room will require at least one oscillating fan to ensure air is continually in circulation. Moving air has a number of benefits for the cannabis plant.

At a minimum, moving air should ruffle all the leaves on a plant to ensure fresh air is available to the leaf stomata. In still environments, stale air can build up on the undersides of leaves around the stomata and hinder efficient gas exchange. This has the undesirable effect of inhibiting plant growth; stems will become weak, leaves will droop, and plant performance will be poor.

Moving air strengthens plants considerably; stems and stalks become thicker and more robust, and end yields will be higher.

Moving air also helps with the wet-dry cycle of the growing medium by supporting evaporation. Moreover, it prevents pathogens caused by moisture buildup on leaves as they transpire. Moulds like nothing more than a moist, warm environment.

AIR EXCHANGE

With a higher budget, introducing an air exchange system stimulates better growth. Air exchange requires an inlet for fresh air and an exhaust for depleted air. With a higher budget still, incorporating a carbon filter into the exhaust system will keep the stink factor to a minimum.

Air inlets are passive and can take a number of forms; however, they are always situated in the lower part of the grow room, either in the floor if the floor is raised, or in a wall. The main consideration is light control when putting perforations into a grow room. A simple slot, vent, or series of holes will provide ample air intake, but can be indiscreet with light. Using a piece of ducting with a bend in it, or configuring a double wall arrangement, stops light escape. The easiest thing to remember is that light can’t go around corners, so introducing an arrangement with a bend of some kind keeps your grow discreet. Also, provide some kind of vermin barrier to dissuade any critters that want to get in and feed on your precious weed.

An air inlet means there will also be an air outlet or exhaust system, ideally with a carbon filter attached. Exhaust systems remove depleted air and heat from the grow room and draw fresh air in. Where possible, it is desirable to exhaust to the outdoors to prevent heat buildup in closed spaces, or to recirculate the same air back into the system. This can often be a challenge, but ducting is your friend when solving air distribution problems.

The capacity of an exhaust fan is dictated by the volume of the grow room. Length × width × height will give the volume of the grow room, and the manufacturer will recommend what fan will be right for the job. It is recommended to go up a size to ensure proper air exchange, and to accommodate any potential increase in the scale of your grow.

CLIMATE CONTROL

Cannabis thrives when the climate is controlled in regard to humidity and temperature, with certain parameters ideal for vegetation and other parameters ideal for bloom.

Humidity can be easily controlled with a dehumidifier; these are also available as double-action units that will add or subtract humidity as necessary. During vegetation, a humid and warm environment increases the rate of growth, while lower humidity and temperatures increase bud development.

Temperatures can be controlled with small, portable, reverse cycle AC units. Many humidity-modifying units and heaters come with built-in thermostats and hygrometers, so they switch on and off as the environment demands. Just set them, and rest assured your weed is booming at every stage; automating the whole thing makes growing life a lot easier.

THE BUILD

Now that you have selected a space that satisfies the demands for a healthy and discreet grow, it’s time to actually build your grow room. There are a number of solutions to create a grow room at home on a budget. This method uses a number of plastic-lined wooden frames to form the walls, base, ceiling, and door. When including a ceiling, supports for the grow lights will need to be incorporated. When dealing with existing walls and ceilings, BE ABSOLUTELY CERTAIN OF THE LOCATION OF ELECTRICAL WIRING. Also, tenants will need to consider the future repair of any surfaces that might be affected when building their grow room.

What you will need:

• A saw
• A stapler that can staple to wood
• Doubled-sided plastic sheet: one side black, the other side white or reflective like Mylar
• Screws
• 4 small hinges
• A drill with a drill bit and a screwdriver bit
• Scissors
• 26 angle plates
• Plastic corner protectors (optional)
• Timber to suit: 4x4cm (or close enough) pine or similar softwood is easy to handle, strong enough, and cheap; your local hardware shop will certainly have this available in a variety of lengths

INSTRUCTIONS

1. To create the top and bottom of your frame, you will require 4x 1.0m + 5x 92cm laths of wood.

– To create the sides of your frame, you will need 7x 192cm laths.

– To create the door, you will need 2x 1.0m laths + 2x 192cm laths.

2. For the top: To affix the laths, drill holes 2cm from each end, and one in the middle for the spax. Do the same to the bottom.

For the door: Drill holes 2cm from each end in the 1m laths. Spax together with the vertical beams.

3. Now that you have created the bottom frame, take one of the 192cm laths, place it in one corner, and affix it with two angle plates. Repeat in each corner.

4. Now that all 4 are in place, place the top and affix all vertical laths to it with angle plates.

5. Measure out the middle between the vertical laths and affix your stabilising beams with 2 angle plates (3 for where they meet the supportive beam of the top frame).

6. Using scissors, cut a piece of plastic/Mylar that will overlap every edge of each frame. Staple the plastic into place on the overlapping edge using plastic corner protectors.

7. Locate the door and screw the 4 hinges into place.

8. Voila, your grow room is now ready to be fitted out.

COLLECTION RACK

Building a collection rack in the floor of the grow room helps keep things neat and tidy. The plants in their pots are placed in this rack so that dirt spills and dead leaves and water runoff are collected then easily removed. When the grow is over, the collection rack is easily swept out and sterilised before the next grow.

To do this, you will build a frame that sits 15cm-deep inside your grow room and is lined with the same plastic used for the walls. This stops the actual floor of the room from becoming filthy and encouraging pathogens.

It is customary to flush plants at regular intervals during the grow, primarily to wash away any fertiliser salt buildup and to keep the medium in a cannabis-friendly nutrient range. Although there is no nutrient buildup in an organic grow, there is always some runoff. However, at the end of the flowering phase prior to harvest, all growing methods require a final flush to increase bud quality. The collection rack will catch all the runoff water, where it can be easily sopped up.

A collection rack can also act as a passive watering system if you are going to leave your plants unattended for a few days. Adding fresh water to the collection rack acts as a de facto reservoir, and plants will wick water up and not dehydrate while you are gone.

GET GROWING

You have now created a space that lets you grow your own cannabis at home. It lets in fresh air for healthy exchange of carbon dioxide, oxygen, and heat; it is light-tight for optimum plant health and discretion, and is clean and easy to maintain. Now, all you have to do is decide on whether you are going to grow organically or with nutrients, and select some killer strains to bring you joy!

For a start, we need to ensure that the space is made completely light-proof. In order to bloom to its peak the cannabis plant needs 12 hours of undisturbed night and 12 hours light.

Complete Ventilation Guide for Your Cannabis Grow Room

While it is often overlooked, proper ventilation is a key aspect of running an efficient and clean grow room. In fact, most cannabis pests and plagues are caused by ventilation issues. Here’s how to properly ventilate your cannabis grow-op for happy plants and hefty harvests!

Read our in-depth guide on cannabis ventilation.

Contents:

Ventilation is a super important yet often overlooked part of indoor cannabis growing. Without proper ventilation, your plants can suffer from stunted growth, disease, and pest infestations. In this guide, we’ll walk you through everything you need to know about properly ventilating your cannabis grow room/tent.

Why Is Ventilation So Important for Growing Cannabis?

Cannabis plants need fresh air for two main reasons:

  • To photosynthesise: Plants need fresh air to fuel the process of photosynthesis, which allows them to turn atmospheric light, water, and carbon dioxide into food.
  • To breathe: Plants respire to turn glucose and oxygen from photosynthesis into energy to fuel their growth.

Without fresh air, your cannabis plants will literally starve to death. But, before this happens, a lack of fresh air in your grow room will create a breeding ground for pathogens and pests. Without proper ventilation, stale, warm air builds up around your plants, creating a hot, humid environment that many pests and plagues love.

Understanding Grow Tent Ventilation

Many beginner cannabis growers get confused or overwhelmed when it comes to ventilation. However, the basic principles of ventilating your grow space are simple; get old, humid air out of your room/tent, and replace it with fresh, cool air from outside.

As you’re reading this, you might be wondering what causes the air in your tent/room to grow warm and humid in the first place. Let’s break it down:

Transpiration

Cannabis plants naturally transpire (or sweat). In fact, this process is essential for plants to move water and nutrients from the soil up into their branches, foliage, and flowers. Cannabis plants transpire through the stomata and cuticles in their leaves, and lenticels (pores found in outer plant tissue such as stems), which creates a pull that draws water up from the roots to the rest of the plant. The water that your plants transpire naturally evaporates into the air in your grow space, gradually driving up relative humidity.

Warmth From Grow Lights

All grow lights emit some form of heat. And, while modern LEDs tend to run cooler than classic HIDs, many growers still opt for the latter (either metal halide, high-pressure sodium, or both) as they tend to produce bigger yields. Without proper ventilation, your grow lights will naturally drive up the temperature in your tent/room.

The best way to keep your grow space ventilated is by using an exhaust system that draws old, warm air out at the top of the room/tent, and draws cool, fresh air from the bottom of your grow space up through the plant canopy. Depending on the size of your space, you can also use simple fans to move air around. Keep reading for more info on how to use extractors and fans.

Essential Tools for a Better Ventilated Grow Room

Here’s a list of all the essentials you’ll need to properly ventilate your grow space.

Extractor Fan

Extractor fans pull old air out of your grow space. Because hot air naturally rises, you should instal your extractor at the top of your room/tent. Some grow lights or reflectors come with an attachment for an exhaust system.

Keep in mind, there are many different extractors on the market, and you’ll need to match the power of your extractor to the size of your grow space. The power of indoor extractors is typically measured in CFM—cubic feet per minute. Here’s how to calculate the CFM you’ll need to properly ventilate your grow room/tent.

Understanding CFM

To calculate the volume of your grow room/tent, multiply its length, width, and height (ideally in feet). For an average 4 × 2ft hobby grow tent, for example, the calculation would look like this:

4ft (length) × 2ft (width) × 5ft (height) = 40ft³

For a grow tent of this size, you’ll want to pick an exhaust fan with at least 40 CFM. As a general room of thumb, we recommend picking a fan with a CFM equal to the volume of your tent/room. This will ensure your fan completely replaces the air in your grow space every minute.

The metric equivalent of this equation is cubic metres per hour, which you can figure out using this handy converter.

Carbon Filter

Carbon filters are designed to scrub contaminants from the air. When attached to your exhaust system, they also absorb the terpenes given off by your plants to cleanse the air you extract from your grow room. Because carbon is very dense (a single gram of activated carbon has a surface area of 3,000m²), activated carbon filters are very effective at dealing with the smell of a cannabis grow room.

Oscillating Fans

Oscillating fans are the final piece of the ventilation puzzle. While they might seem simplistic and cheap, strategically placed fans can encourage efficient airflow around your grow room. Not only will the breeze strengthen the stems of your plants, but it’ll help prevent the build-up of stagnant air around your space, reducing the risk of pests or plagues ruining your crop.

Choosing Between Passive and Active Intake

Air intake basically refers to how you bring air into your grow room. Passive intake relies on natural airflow through holes or vents in the walls of your room/tent. Active intake, on the other hand, works by pulling air into your grow room using an intake fan. This ensures much higher air circulation, making it, by far, the best way to ventilate your grow room. The CFM of your intake fan should be slightly lower than that of your exhaust to ensure negative air pressure in your room/tent.

The Importance of Negative Air Pressure

As indoor growers, it’s our job to recreate Mother Nature’s conditions and give our ladies the best possible growing environment. Measuring the air pressure in your grow tent gives you extra control over your plants’ environment and, more precisely, helps ensure optimal airflow.

Ideally, you’ll want the air pressure in your grow space to be negative; this indicates that there is more air leaving your room than there is coming in, which will make it easier for you to control the temperature, humidity, and CO₂ in your grow-op, while also minimising the smell of your operation (as old air isn’t building up around your room).

Different Extractor and Carbon Filter Configurations

As you might expect, extractor and carbon filter systems can be configured in different ways, all with the end goals of keeping plants healthy and odour at a minimum. Let’s examine the different options and their pros and cons.

Carbon Filter > Extractor > Exhaust

This is arguably the most common way to instal an exhaust system, fan, and filter inside a grow tent. Installing the carbon filter at the beginning of your exhaust system scrubs the air before it’s pushed through your ducts and brought outside.

  • Air is filtered before it reaches your fan, preventing damage from airborne contaminants.
  • Takes up a lot of space and may not be well-suited for small tents/rooms.

Carbon Filter > Lighting > Extractor > Exhaust

This is for growers with an enclosed venting system on their lights. Instal the filter before your grow lights, and your extractor and exhaust fans after your light fixture.

  • Makes for an easy, compact exhaust setup.
  • Only works with grow lights with enclosed venting.

Extractor > Exhaust > Carbon Filter

Some growers opt to instal their filters right at the end of their exhaust system. This way, the air from their room/tent is scrubbed just before it’s blown outside.

  • Good solution for growers working with limited space, as the carbon filter can be installed outside the grow room/tent if necessary.
  • Pulls contaminated air through the fan, which may cause damage.

Should You Instal Your Extractor Fan Inside or Outside Your Grow Tent?

This is a common question amongst rookie growers. In general, we recommend installing your extractor fan and all parts of your exhaust system inside of your grow tent to minimise noise pollution. If you’re low on space or struggling to manage the heat inside your tent, however, feel free to instal your fan outside the tent. Wherever you choose to instal your extractor, it’s crucial your exhaust system is airtight.

How to Ventilate a Grow Tent

Most indoor home growers opt to grow in tents. Luckily, most modern grow tents have vents or ports to accommodate a ventilation system. Here are the basics on installing an exhaust system in your grow tent.

Set Up Your Filter and Exhaust Fan

Instal your carbon filter, followed by your exhaust fan. We recommend installing both prior to installing your grow lights, as setting up ventilation around your lights can be tricky.

Instal Your Grow Lights

Once you’ve installed your filter and fan, instal your lights using rope ratchets.

Connect Everything With Ducting

Once your lights, filter, and fan are installed inside your tent, connect everything with ducting. Remember to use ducting clamps to hold everything in place, and keep some duct tape handy to cover up any tears in your system.

Pull More Ducting From Your Tent Outdoors

Outside your tent, use ducting to bring air from your fan to a window (or wherever you’re going to exhaust the hot air). Keep the ducting path as straight and short as possible to maximise efficiency.

Use Active or Passive Intake to Draw New Air Into Your Tent

If you’re relying on passive intake, remember to ensure that the intake vents in your tent are open. Also, keep a window open near your grow room to help replace the hot air being vented out of your tent.

If you’re using active intake, instal your intake fan at your tent’s intake vent.

How to Ventilate a Micro Grow

Micro-growers cultivating a plant or two in a cabinet or wardrobe can keep ventilation very simple. In fact, ventilating a micro-grow can be done for next to no money. Opening a window near your tent/cabinet/wardrobe a few times per day, and using oscillating fans as necessary, can be enough to properly ventilate your grow. Growers using LED, CFL, or low-power HID systems (250W or less) shouldn’t have issues with heat. Meanwhile, dealing with humidity in a micro-grow can be as simple as using a dehumidifier.

How to Ventilate a Greenhouse

Greenhouse growers should make sure they have multiple vents that can be opened and closed as required. Most basic, plastic-covered greenhouses have ventilation flaps that can be opened and closed manually. Worst case, you can open up the doors a little or remove a windowpane from glass greenhouses.

Letting the breeze in makes all the difference. A greenhouse can get really humid, especially when it’s packed with lots of leafy cannabis plants transpiring. Indoors or outdoors, as plants mature, they will expel more water vapour and increase the relative humidity in the space. Good airflow is essential in every growing area. During late bloom, most greenhouse growers with fat flowers will open up all vents, and maybe even DIY a few extra to avoid bud rot.

How to Be Discreet When Ventilating Your Grow Tent/Room

It’s advisable to invest in some wicker blinds and secure them in front of the window you plan to use for ventilation. It will cover up what’s going on in the grow room and still let air in. Then, you can start connecting up your ducting. Many will just board up the window by drilling some plasterboard or plywood onto the window frame with a cut-out hole for the ducting to pass through. A quick tip is to cut out the hole first!

Odour Control

The tried and trusted trio when it comes to eliminating cannabis odours are hands down the intake fan, exhaust fan, and carbon filter combination. If you are already investing in fans and ducting, it just makes sense. For the grower that wants to be certain odour is under control, this system is the best.

However, there are some promising odour-eliminating devices that dispense neutralising agents round the clock. That being said, these products are currently unproven technologies.

Final Thoughts on Managing Airflow in Your Cannabis Grow-Op

While managing airflow in your cannabis grow room might seem tricky, it doesn’t have to be. As long as you follow the tips in this guide, and focus on constantly replacing the air inside your tent or room, your plants will have the perfect conditions to flourish in.

Is your grow-op properly ventilated? Click here for an in-depth guide on cannabis grow room ventilation, so you can grow bigger, healthier weed plants.