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Thread: Ventilation - The basics

  1. #41

    Join Date
    Feb 2014
    Thanked 413 Times in 132 Posts


    Brilliant thread Jesse, thank you. I`ll be reverting back here in the near future!

  2. The Following 2 Users Say Thank You to My Tent Or Yours For This Useful Post:

    Jesse Pinkman (14-04-15), Oxy (14-04-15)

  3. #42

    Join Date
    Jan 2014
    Thanked 85 Times in 62 Posts


    Great thread, just a quick question.
    Is it easy to maintain a warm enough temp whilst the lights are off if you have intake fan as well? I have two heaters and my extraction fan is connected to a fan controller set to 25 degrees?
    In the past I've just had the air vents near to an air brick open but with tent being in cellar there isn't much air flow. Would assume the intake fan will hugely increase CO2 via this.


  4. The Following User Says Thank You to Tanman For This Useful Post:

    Jesse Pinkman (11-03-16)

  5. #43

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    Mar 2016
    Thanked 2,419 Times in 910 Posts


    nice read here.

  6. The Following User Says Thank You to Fwank For This Useful Post:

    Jesse Pinkman (11-03-16)

  7. #44

    Join Date
    Apr 2015
    Thanked 482 Times in 217 Posts


    Quote Originally Posted by Jesse Pinkman View Post
    Cheers bud
    That looks nice setup, must pull like a train on the short run you have onit! Not so mention saving room in the tent.
    Nice work oxy
    I'm gona try this. Having temp trouble

  8. #45

    Join Date
    Apr 2015
    Thanked 568 Times in 202 Posts


    Quote Originally Posted by Jesse Pinkman View Post
    Some guidance on the importance of air to growing and in the setup up of grow rooms, hopefully you will find helpfull

    Fresh air:

    Fresh air is essential in all gardens. Indoors, it could be the difference between success and failure. Outdoor air is abundant and packed with carbon dioxide (CO2) necessary for plant life.
    For example, the level of C02 in the air over a field of rapidly growing cannabis could be only a third of normal on a very still day. Wind blows in fresh CO2 rich air. Rain washes air and plants of dust and pollutants. The outdoor enviroment is often harsh and unpredictable, but there is always fresh air, Indoor gardens must be meticulously controlled to replicate the outdoor atmosphere.
    Carbon dioxide and oxygen provide basic building blocks for plant life. Oxygen is used for respiration- burning carbohydrates and other foods to provide energy. Carbon dioxide must be present during photosynthesis. Without C02 a plant will die. Carbon dioxide combines light energy with water to produce sugars.These sug- ars fuel the growth and metabolism of the plant. With reduced levels of C02, growth slows to a crawl.
    Except during darkness, a plant releases more oxygen than is used and uses much more carbon dioxide than it releases.
    Roots use air, too. Oxygen must be present along with water and nutrients for the roots to be able to absorb nutrients. Compacted, water- saturated soil leaves roots little or no air, and nutrient uptake stalls.

    Air Movement:

    Air ventilation and circulation are essential to a healthy indoor harvest. Indoors, fresh air is one of the most overlooked factors contributing to a healthy garden and a bountiful harvest. Fresh air is the least expensive essential component required to produce a bumper crop. Experienced growers understand the importance of fresh air and take the time to set up an adequate ventilation system.

    Three factors affect air movement: stomata, ventilation, and circulation.


    Stomata are microscopic pores on leaf undersides that are similar to an animal's nostrils. Animals regulate the amount of oxygen inhaled and carbon dioxide and other elements exhaled through the nostrils via the lungs. In cannabis, oxygen and carbon dioxide flows are regulated by the stomata. The larger the plant, the more stomata it has to take in carbon dioxide and release oxygen. The greater the volume of plants, the more fresh Co2 rich air they will need to grow quickly. Dirty, clogged stomata do not work properly and restrict airflow. Stomata are easily clogged by dirt from polluted air and sprays that leave filmy residues. Keep foliage clean. To avoid clogging stomata, spray foliage with tepid water a day or two after spraying with pesticides, fungicides or nutrient solution.

    ^^Microscopic stomata located on leaf undersides must remain clean ond unstifled by humidity to promote rapid growth.


    Plants use all co2 around the leaf within a few minutes. When no new co2 rich air replaces the used co2 depleted air, a dead air zone forms around the leaf. This stifles stomata and virtually stops growth. If it is not actively moved, the air
    around leaves stratifies. Warm air stays near the ceiling, and cool air settles near the floor. Air cir-culation breaks up these air masses, mixing them together. Avoid these would be problems by opening a door or window and/or installing an oscillating circulation fan. Clip on or large floor standing oscilating fans are very inportant in any groom as should be overlooked at your plants peril. Air circulation also helps prevent harmful pest and fungus attacks. Omnipresent mold spores do not land and grow as readily when air is stirred by a fan. Insects and spider mites find it difficult to live in an environment that is constantly bombarded by air currents.


    Fresh air is easy to obtain and inexpensive to maintain it is as simple as hooking up and placing the proper-sized exhaust fan in the most efficient location. An intake vent may be necessary to create a flow of fresh air in the room.
    A 10-foot square (0.92 m2) garden will use from 10 to 50 gallons (38 to 190L) or more of water every week. Plants transpire (similar to evaporation) most of this water into the air. Every day and night, rapidly growing plants transpire more moisture into the air. If this moisture is left in the grow room, humidity increases to
    100 percent. which stifles stomata and causes growth to screech to a halt. It also opens the door for pest and disease attacks. Replace moist air with fresh dry air, and transpiration increases stomata function properly, and growth rebounds. A vent fan that extracts air from the grow room is the perfect solution to remove this humid, stale air. Fresh air flows in through an intake vent or with the help of an intake fan.
    Ventilation is as important as water, light, heat, and fertilizer. In many cases, fresh air is even more important. Greenhouses use large ventilation fans. Grow rooms are very similar to green houses and should follow their example. Most grow rooms have an easy-to-use opening, such as a window in which to mount a fan, but secu- rity or room location may render it unusable. If no vent opening is available, one will have to be created.
    All grow rooms require ventilation. This system could be as simple as an open door or window that supplies and circulates fresh air throughout the room, but open doors and windows can be inconvenient and problematic. Most growers elect to install a vent fan. Some growers need to install an entire ventilation system including ductwork and several fans.
    A vent fan pulls air out of a room four times more efficiently than a fan is able to push it out. Vent fans are rated by the amount of air, measured in cubic feet per minute (CFM) or (square meters per hour [m~/h]) they can move. The fan should be able to replace the air volume (length x width x height = total volume in cubic feet) of the grow room in less than 5 minutes. Once evacuated, new air is immediately drawn in through an intake vent or with the help of an intake fan. (Covering the intake vent with fine mesh silkscreen will help exclude pests.) An intake fan might be necessary to bring an adequate volume of fresh air into the room quickly. Some rooms have so many little cracks for air to drift in that they do not need an intake vent.
    Do not set up a circulation fan in the room and expect it to vent the area by pushing air out a distant vent. The circulation fan must be very large to adequately increase air pressure and push enough air out a vent to create an exchange of air. A vent fan, on the other hand, is able to change the pressure and exchange the air quickly and efficiently.
    Blowers with a balanced, well-oiled wheel run most quietly. Felt or rubber grommets below each foot of the fan will reduce noise caused by vibrations. Run motor at a low RPM to lessen noise.
    In-line fans are designed to fit into a duct pipe. The propellers are mounted to increase the air- flow quickly, effortlessly, and as quietly as possible. In-line fans are available in quiet, high quality models that run smoothly.
    Propeller or muffin fans with large fan blades expel air through a large opening, and are most efficient and quiet when operated at low RPM. A slow-moving propeller fan on the ceiling of a grow room will quietly and efficiently move the air.
    Hot air rises. Adept growers locate air exit vents in the hottest peak of the room for passive, silent air venting. The larger the diameter of the exhaust ducts, the more air that can travel through them. By installing a big, slow-moving vent fan in this vent, hot stale air is quietly and efficiently evacuated. A fan running at 50 RPM is quieter than one running at 200 RPM. Smart growers install 12-inch ducting and inline fans. Most often, the vent fan is attached to ducting that directs air out of the grow room. Flexible ducting is easier to use than rigid ducting. To install, run the duct the shortest possible distance, and keep curves to a minimum. When turned at more than 30° much of the air that enters a duct will not exit the other end, keep the ducting straight and short.

    Intake fans:

    Many rooms have enough fresh air coming in via cracks and holes. But other grow rooms are tightly sealed and require fresh air to be ushered in with the help of an intake fan. An intake fan is the same as an exhaust fan, except it blows fresh air into the room. The ratio of 1 to 4 (100 CFM [m3/H] incoming and 400 CFM [m3/h] outgoing) should give the room a little negative pressure. Delivering fresh air to plants ensures they will have adequate co2 to continue rapid growth. One of the best ways to deliver air directly to plants is to pipe it in via flexible ducting. Ingenious growers cut holes in the intake ducting to direct air where it is needed. The air is dispersed evenly throughout the room.
    Always make sure fresh air is neither too hot nor too cold. For example, one friend that lives in a hot climate brings cool fresh air in from under the house, where the air is a few degrees cooler than ambient air.


    When installing a vent fan, security concerns dictate that no light or odor escape from the exterior vent while allowing ample air release. This can be accomplished in several ways. Baflle or turn the light around a corner to subdue escapes, termination should be high as possible so the odor disperses above most people's heads. One of the best vents is the chimney. The vent fan is then placed near the ceiling so it vents hot, humid air. Check for light and air leaks. Set up the fan and go outdoors after dark to inspect for light leak.

    Hope this helps folks

    Peace bitches

    great read, some advice if possible please, I have a 120x120 and a rvk125 with 2 settings, i have it on the lowest setting but my tent is in a cold place, I have a 3inch fresh air inlet with a thick sock over the end but the air expelled is coldish, would putting a couple of extra bends in my outlet help by reducing the airflow

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  9. #46

    Join Date
    Jan 2012
    gettin mangled
    Thanked 3,814 Times in 2,157 Posts


    Get rid of any cold intake ducting

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