Open vs Closed Loop Grow Rooms: Which Setup Is Superior?

open vs closed loop grow rooms

­­Growing indoors provides you the power to influence all necessary inputs for growing big, healthy, cannabis plants. This includes lights, nutrients, water and humidity, ventilation as well as temperature.

Instead of being dependent on weather and soil, you can optimize your production for maximum yield and who doesn’t like a good fat thicc MAXIMUM YIELD!

how to grow cannabis in home beginners

Benefits of Growing Cannabis Indoors

If you’re on the fence about growing your own weed then let us help you make up your mind! Here are some of the multitude of benefits you can reap when you sew your own seed!

  • High-quality: Although it’s more resource-intensive than growing outdoors, you can control every aspect of your environment and what you put in your plant, so growing indoors will allow you to dial in your setup.
  • Adaptability: Live in an apartment or a small house? You can grow cannabis practically anywhere, even people who don’t have a backyard or a lot of extra space.
  • Multiple harvests: Unlike outdoor growing, you aren’t tied to the sun and the seasons. You can let your plants get as big as you want, flip them into flower, harvest, and then start another batch right away.
  • Privacy and security: You may want to conceal your crop from judgmental neighbors and definitely from potential thieves. Growing indoors allows you to grow discreetly.

If you’re still not convinced, check out our 10 Reasons You Should Grow Your Own Supply of Cannabis article here to finally give you that kick in the butt you need to go all-in and start your own personal mini farm!

Seedo Home Cultivator
Seedo Smart Box Home Cultivator overview

Requirements for Healthy Growth & Big Yields

Whether growing marijuana plants indoors or outdoors, you will need to ensure that it gets the proper amount of these six resources.

  • Light
  • Air
  • Grow medium
  • Temperature
  • Nutrients
  • Water

Your garden is a living breathing system that needs to take in fresh air and expel waste air and heat. The atmosphere inside of your grow room is just as important as the grow light you choose.

If your grow light isn’t adequate for the size of your plants canopy, but the air inside of your grow area is set up properly your plants will still grow. However, if you have a quality grow light but the air in your garden is toxic, you will not grow anything.

Open-loop Grow Rooms

Open-loop grow rooms constantly provide fresh air to the plants in one of two ways. Either an intake fan that pulls air from an outside source or a passive exhaust system pulls in fresh air by forcing old air out through an exhaust duct.

The outside source of fresh air could be a separate room, the hallway, an attic, basement, cracked window, or even directly from outside if the air is filtered for bugs and large particles.

There are pros and cons of using each one of these sources for fresh air but the point is, open-loop systems will have new, fresh air continuously pushed or pulled into the grow space.

Most growers prefer using the exhaust to push out the old air. This creates a passive intake system which means that new air will be pulled into the room by old air being pushed out.

CO2 and Open-loop Grow Rooms

Open-loop systems should not be paired with Co2 generators. This is because the air within your grow room is continually being replaced. The Co2 that’s injected or generated within the room will always be removed or diluted and will be useless.

Typically, open-loop systems do not require an air conditioner or dehumidifier. This is because the air within the grow space is constantly being replaced so heat and humidity do not have a chance to build up.

Since open-loop systems require fewer components, you will save money on your electricity bill each month.

Closed-loop Grow Rooms

A closed growing environment differs from the customary grow room set-up in that it does not connect to the external environment and runs on a closed-loop.

Normally, grow room air is vented to the outside while outside air is drawn in to replace the air being evacuated. This creates an “open door” for a host of problems and can limit the amount of control you can take over your growing environment.

Closed-loop systems use Co2 gas to provide the fresh air within the grow room and do not rely on intake systems in the same way an ‘open loop’ grow room would.

The exhaust within the grow room is controlled and is only used when temperatures rise to an unsuitable level, the humidity is too high, or the Co2 levels have risen to an unsafe level.

Why Co2?

A plant must have the proper Co2 levels in the air to be a healthy plant, with a healthy immune system, which will fight off molds, diseases, and bugs, and produce healthy plants.

Outside, the air has about 400-450 ppm (parts per million) of CO2 all the time. For plants, this is a happy level of CO2.

However, at levels around 200 ppm, a plant can start choking or suffocating. At levels this low the plant will not be healthy and may even die.

Plants can use levels of CO2 up to 2000 ppm 4-5 times that of normal ambient levels and achieve the best growth and production. Performance can be enhanced by adding CO2 to the room, increasing the levels considerably. This can only be done efficiently in a sealed or closed room.

Importance of Grow Room Temperature Control

Temperature is important to plants as it sets the stage for growth and proper development of the plant. Young plants tend to prefer higher temperatures. This is because it allows them to absorb more moisture in the air through the stomata in the leaves while the root system is still developing.

You should slowly drop temperatures as your plant moves to veg, and then to flower and harvest. Proper temperatures can also reduce the risk of mold and mildew. The temperature will depend on the kind of crops and growth stages being grown.

The air conditioner is the main component of a sealed closed-loop room. A true AC is recirculating the same air in the room. The air never leaves the room.

These types of AC units are usually referred to as split unit ACs. It has vents in every room putting cold air into the room, and also has a return duct of equal CFM (cubic feet per minute) creating equal pressure, cooling the same air over and over again.

This allows CO2 to be run efficiently and not be wasted as the air is moving and recirculating. The only loss of CO2 is that which the plants have consumed. The AC also acts as a natural dehumidifier, so you need to watch your humidity levels in case the AC is dropping the levels in the room below ideal.

Popular Growing Solutions for Different Situations

Growing is such a broad activity, ranging from personal use hobbyists to startup mega-growth boutique cultivars and thus the type of grow facility can vary greatly depending on the goals of the grower.

You can start with something as small as a self contained grow cabinet in your apartment and scale all the way up to purpose-built open loop grow facilities all the way up to the mecca of growing full plot outdoor yields.

We highlight some of the more common growing situations below and what you should consider before jumping into any of them head-first.

Gorilla Grow Tent Lite Line review

Grow Tents

Grow tents have the wrong port placement and sizing, creating an inadequate set up for closed-loop growing. Thin poles cannot properly support your tent, fans, reflectors, and filters. Companies like SuperCloset and Gorilla Tents are at the top of their game when it comes to scalable tent solutions.

Sizes are not big enough and do not allow you to move throughout your room after setting up your desired grow setup. Lower heights create heat pockets on your canopy and do not allow for significant yield or production.

Grow tents are best left for “learning” situations where you have the space in another larger room or facility to set up a tent and have the capital to invest in quality fans as well as LED light systems. Hydroponic systems are also important to producing consistent quality flower yields.

home marijuana cultivation

Indoor vs. Outdoor Growing

It’s a decades-old debate with equally stubborn supporters on both sides: What yields better results—indoor- or outdoor-grown cannabis?

All growers have their preferences, practices, and requirements. And there’s a good chance that they’ll have strong opinions about what’s best for their crop.

Pros of Outdoor Cultivation

There is no 100% correct or 100% incorrect method of growing. A lot of growers like the outdoors because it’s the most natural form, as that is how the plant evolved. There is also local pride that can be had with growing a regional specific crop, of any type!

Pro 1: Low carbon footprint and lower costs

Outdoor cannabis requires far fewer resources and is less expensive to produce than plants are grown indoors. Outdoor uses the natural environment to fuel its growth, and it does not require artificial, high-intensity lighting.

Compared to indoor-grown cannabis, outdoor plants typically require fewer soil amendments, fertilizers, pesticides, and fungicides. Indoor power usage and water usage are very resource consumptive.

Pro 2: Complements the plant’s natural life cycle

For millions of years, plants that undergo photosynthesis have evolved and flourished under the rays of the sun. Scientists report that cannabinoid and terpene production is greatest in ambient light. Natural light is much more complex than what even the best grow lights can mimic.

Pro 3: Ecology and resiliency

Acclimated to local conditions, unique landrace varietals native to specific bioregions (Acapulco Gold, Panama Red, etc.) have adapted to deal with local pests and other threats. Because outdoor crops are part of the ecosystem, the plant interacts with the elements and this helps to build flexibility and resistance to temperature fluctuations and potential attacks.

Pros of Indoor Cultivation

Indoor cultivation has been the faster growing method recently, partially because new cultivars may not be able to afford the land required for outdoor growing and because growing indoor can be better for business-minded growers.

Pro 1: Year-round cultivation

Indoor cultivation isn’t seasonal. With the right set-up, indoor growers could theoretically produce cannabis any time anywhere in the world. They are not limited by adverse environmental conditions that may impact outdoor farmers who can only grow in favorable climates

Pro 2: Control over growing conditions

Indoor cannabis plants are more sensitive than outdoor plants and, therefore, a cultivator must carefully monitor and adjust various factors within a closed, interior grow-room. A skilled indoor grower can control all aspects of light, airflow, soil, and nutrients that affect the plants.

Pro 3: Product standardization

As the cannabis industry matures, consistency and predictability will be required to standardize a medical product and to gain approval in the pharmaceutical sphere. Standardization is necessary for a reliable, reproducible product that can be researched during clinical trials

Pro 4: “Boutique” production

Cannabis consumers want a nice looking product with a stellar aroma. Dispensaries place a premium on “bag appeal” when displaying cured cannabis flower tops.

A skilled indoor grower can carefully manipulate various environmental factors to accentuate desired traits, resulting in cannabis that looks great and smells divine.

HerbCEO Summary

Ultimatley, whether you go closed loop or open loop, indoor or outdoor, large vs micro scale, everything will be dependent on your unique situation.

This means things like secrecy vs transparency (public/outdoor vs private/indoor), your budget (how much equipment can you afford), and your goals (how much crop do you need to produce).

If you are just starting out on your self-cultivation journey here is our beginner guide to growing weed that is worth your perusal.

If you’ve grown before and are looking to take your game to the next level/increase the quality and volume of your yields, then we’d recommend our roundup of the best continuing education cannabis grower resources here which includes expert forums, online courses and of course, books!

Master growers learn to operate and cultivate bountiful yields in a multitude of different environments and it is this diversity in growing that produces the wonderful variety in flowers consumers and patients enjoy today.

Just remember, there is no “correct” solution or “wrong” solution, they are all predicated on the growers own goals and by what they hope to achieve with their growing operation.

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