If you are bothering to grow your plants indoors under HID lights, you probably care quite a bit about them and want them to be healthy and produce well for you. If this is the case, you need to be aware of the environmental factors that will affect your plants' growth the most. Probably the largest problems associated with growing indoors are ventilation or Carbon dioxide related. The current of air that circulates in a grow room is as important as light, water, heat and nutrient. Proper ventilation acts as a mediator between light and water, removing excess heat and humidity, while providing plants with a healthy supply of CO2.

The amount of control you will need to exercise over the environmental factors in your room will greatly depend on the scale of your growing area - the number of plants, the number of lights, the size of the room, and whether or not you are supplementing with CO2. It also depends on the kind of result you wish to get.

Automated controllers ARE expensive, but they really do make a large difference. They keep the conditions at the perfect level for your plants and they will reward you with gorgeous and boutiful produce. With each environmental factor that gets tuned in to the correct range, the plant growth will become that much more healthy and robust.

You can achieve excellent results by using timers and innovation, however most commercial nurseries have automated controllers in their greenhouses. If you are growing plants for profit and want to compete on a commercial base..chances are you would benefit from some automated controls as well. We go over the basics and necessities as well as some of our favorite choices below.

Air circulation in your garden is very important. It should not be neglected when you are planning your indoor environment. The circulation within the room should be constant and breezy. Plants breathe through their stomata which reside on the undersides of their leaves. Therefore, the air in the room must be make accessible to these sites. This is not that difficult to do and depends on the space involved.

In a closet or other small space, a small circulating fan like the Super Turbo should do the trick. For larger applications, an industrial fan should be positioned in such a manner as to facilitate a current of air which sweeps around the room in a circle. In a 10' x 10' space, one industrial fan combined with a wall mounted circulating fan should be sufficient. Larger spaces may need double or triple the amount of fans.

To provide ample CO2 to plants, fresh air must be brought in continually, or it can be supplied via a CO2 emitter or generator. Getting fresh air into your grow room can be as simple as an open hole with a protective screen, or you may use a vent fan.(if you choose to supplement your grow room with CO2, a fresh air intake is not necessary.)

It is very important to keep your room's heat and/or humidity levels in check. Growing plant produces humidity. Hot lights product heat. If you are using CO2 enrichment you will have to pay extra attention to this area, as rooms can get extra hot and humid. (This discussion assumes you are not using CO2 enrichment...if you are using or plan to use CO2 enrichment, check the section on CO2, Heat and Humidity

The easiest method is to install a vent fan on a timer. The timer will regularly turn the vent fan on and exhaust hot and/or humid air. An intake fan could be used as well, to bring cool outside air in. While this will help considerably it is still a very rough method of control.

We prefer more precise humiudty control and therefore use a vent fan powered by an automated controller which will keep the Relative Humidity (RH) level within a set perameter. The controller will sense the RH level in the room and will turn on the vent fan whenever humidity levels reach too high. It will turn the fan off when the RH level has fallen below your chosen setpoint. Here’s an example of a controller we like, - the RHC-1 from Green Air.

If heat is your main concern, we suggest using a vent fan and coupling it together with a Tempstat. When temperatures get too high, the tempstat will turn the vent fan on until the temperature drops below your chosen set point. In most idoor environments, lighting is the major source of heat. Air Cooling your lights is another possiblen solution. Most horizontal reflectors can be easily converted to air cooling by using a lens, the correct hose fittings & ducting to a 265 CFM vent fan.

Proper venting always takes at least one exhaust fan. With the help of Flexible Ducting, venting can be directed through roofs, around tight corners and even through walls. Flexible ducting is also a good way to reduce the noise from your exhaust fan (by allowing you to move the fan further away). Remember, the more ducting you use, the less air the fan will move. Good venting helps with odor problems, too. Odiferous air can be exhausted from the grow area through an ozone generator, such as the Serfin Wave.

Buy a fan that will replace the volume (cubic feet) of air in your grow room air in about 5 to 8 minutes or less. The stale air is immediately replaced by fresh air drawn from around the doors or windows. To calculate the room size multiply width by height to get the total cubic feet of your room. Here's an example: a 10x10x8-foot room is equal to 800 cubic feet. A vent fan should exchange the air within 5 minutes, so for an 800 cubic foot room you'll need a fan capable of moving 160 cubic feet per minute.

The process of plant photosynthesis relies on a trinity of three elements -- water, light and carbon dioxide. Plant metabolism is regulated primarily by the availability of these three essential requirements. If any of these elements are at levels below what the plant can use for maximum efficiency, it will only be able to perform at that level and no greater.

Enriching a grow room with CO2 allows your plant to use excess water and energy stored in their leaves, resulting in dramatically increased growth. Think about this: the average outdoor CO2 level is 300 to 600 parts per million (ppm). But plants can use much more than that. Here's the wonder of growing indoors, a grow room can be enriched to a level of 1000-2000 ppm. That's 3 to 6 times the amount of CO2 encountered outdoors. The result? Plants grow faster, fuller and have more zest for life. When using elevated levels of CO2, plant growth rates can increase by as much as 100 to 200%. The average increase is closer to 50%, which is still incredible!

In the presence of carbon dioxide, plants prefer warmer temperatures. Heat helps their respiration system increase their metabolism to accomodate the extra CO2. Plants use CO2 to form new sugars, which in turn form plant matter. The byproduct is pure oxygen. Faster respiration levels mean humidity levels increase. Most gardens are generally dry, so the added moisture is welcome. However, gardens using CO2 produce excess moisture and are consequently susceptible to rot and its nasty pal, fungus. Some form of humidity control (vent fans and in large gardens, dehumidifiers) should be employed to keep humidity at an optimum level.

Using Bottled CO2
Probably the most common way of enriching a grow area with CO2 is by using bottled gas. The bottled gas is released via a CO2 Injection Valve consisting of a pressure gauge (monitors how much gas is in the tank), a flow meter (monitors the amount of gas being released) and a solenoid valve (turns flow of gas on and off). Some method of controlling the valve is employed, whether it be a timer or a CO2 controller. Plastic tubing with holes drilled in it is placed around the ceiling of the room. CO2, being heavier than air then cascades down onto the garden.

A great benefit to this kind of system is that it does not create heat as a byproduct. The disadvantage to using this system is that the CO2 tank must be regularly refilled. We offer a dual switch over valve which allows for the use of two tanks, and less frequent refilling trips.

CO2 Generators
Most CO2 Generators create CO2 as a byproduct of burning propane or natural gas. They are built to run off of liquid propane tanks or a natural gas line. The natural gas option is preferable to most growers, as it eliminates the need to constantly refill tanks. Most buildings have a natural gas line, although you may need to have it extended to reach your grow area. We do not suggest you do this on your own. Get help from a professional!

The generators we sell are Green Air CO2 Generators which provide CO2 far more economically than any other means of enrichment. A constant burning pilot is used to ignite the gas when the generator is turned on. A thermocouple is used to monitor the pilot flame. If the pilot flame is lost, a safety valve will close so that unburned fuel will not be released into the enclosure.

When enriching a room with CO2, the idea is to produce just enough to be effective, but not so much that precious CO2 is wasted. This Simple CO2 Setup is a low tech way of handling this, using a timer.
if you go this route, we suggest using a timer that is capable of running very precise, timed intervals such as this CO2 Timer. Even better is to use a timer that is made for CO2 enrichment such as the Cyclestat. (The Cyclestat is excellent because it is available with a photosensor that turns off CO2 enrichment in the dark sense plants need to use it - it will save you money!)

Automated CO2 control equipment usually controls venting actions as well as CO2 quickly pays for itself by providing a method of accurately controlling CO2 producing equipment. Some control options work by actually sensing the amount of CO2 in the room and functioning equipment according to actual ambient values. Read the section below this one for more information on CO2 Enrichment, Temperature and Humidity.

When using CO2 it is difficult to maintain optimum levels in a grow area employing an air intake. For this reason, it is important that the room be a 'closed' system. Oxygen tends to push additional CO2 out of a room, and since oxygen is created by plants, it is only necessary to vent in order to lower temp and humidity levels within the space.

One of the biggest problems new growers encounter when using CO2 is that they over-enrich the room. When CO2 levels approach 2000 ppm, most plants will die. High levels of CO2 are also toxic to humans and pets.

CO2 enriched rooms can get extremely wet. This increase in Relative Humidity is due to the fact that the plants’ metabolic processes are occurring at a more extreme rate and water is flowing up through the roots and out of the leaves quickly. Most plants do not thive in an overly humid environment.

When the level of humidity gets too high it needs to be removed with either a vent fan or a dehumidifier. The most common problem for most growers is finding the fine balance between exhausting moist air, enriching a room and keeping the temperature at the right level. If this is done incorrectly, CO2 will be exhausted with the air and plants will not get the benefit of the CO2 enrichment. There are many solutions to this conundrum and we will tell you two of our personal favorites. Feel free to modify these examples to fit your needs.

If you are using a CO2 emitter system, we suggest use of the Compugas. It is very affordable, easy to use and extremely efficient. It will turn CO2 enrichemnt on and off at predetermined intervals, based on basic information you provide. (Room dimensions, desired ppm, cfh of emitter) It does all the calculations for you and creates a CO2 on/off schedule coupled together with vent fan control for airing out the room. It will turn the CO2 OFF before it turns the vent fan ON and vice versa. It comes standard with a photosenesor which ensures CO2 will be turned off in the dark when plants are unable to use it anyway.

For larger situations when a CO2 generator is employed, heat and humidity are even more of an issue. In this type of growing situation, we highly recommend the grower invest in the CDMC Package from Green Air, as well as a Cooling/Humidity Controller CT-DH-3. For a detailed explanation of how this works, click on the two product links above or click here to see how they work together.

Another difficulty is encountered in a grow area with more than two lights. In rooms with more than two lights, it is difficult to use CO2 without adding an air conditioner. HID lights are mighty heat generators, so having more than two will invariably cause problems. A CO2 generator (not a tank) will also add excess heat. We recommend using an air conditioner in these situations. Yes, it is possible to avoid using an air conditioner, but it's tricky. You must use a carefully designed system using a CO2 controller and air cooled lights to avoid wasting your precious CO2. We think it's easier to whip out your trusty portable air conditioner.

Nutrient and pH control allows the grower to not only monitor these very important growth elements, but also allows for precise control. This control is achieved through the use of set points and duration doseage times. It's a very simple concept. You program in the set points you wish for and the controller will dose the reservoir with a set amount of nutrient or pH adjuster to bring the reservoir readings to the right level.

There are two delivery systems that are available for these controllers. One is gravity fed with the use of solenoid valves. The second method is with a pump delivery system which eliminates the restriction on placement. (In gravity fed systems, the nutrients must be placed directly above the reservoir.) Both of these methods work well and once you have become acquainted with the parts involved, you will find them very easy to use.

There are several nutrient and pH controllers on our website. They vary in price and quality.

The HydroGeneral is an industrial grade controller and one of the best on the market. Unlike other controllers which rely on gravity to do the work, the HydroGeneral uses peristaltic pump kit to control its nutrient and pH dosing. This unit is nice because it is very simple to set it up right out of the box.

Another good controller is the AutoGrow. It uses high quality solenoid valves and comes with everything you need for set up right out of the box. It can be custom fitted for stand alone pH or TDS dosing or it can handle both.

The professional grower may be interested in the Nutridose II. This controller is the most industrial of those we offer and may be used with peristaltic pumps or with solenoid valves. It also has remote accessing capabilities, but it is slightly more complicated to use.

All of these controllers are capable of controlling both temperature and humidity and include some form of CO2 control. (some use a cycle timer, where others use a CO2 monitor.) They all include a a cycle timer and an auxilliary timer. You will find that some of these controllers have nutrient and pH controlling capablilites as well.

The GHC-4 controller is the most powerful and versatile of all the Green Air Controllers, providing advanced features - synchronized atmospheric and nutrient management with remote monitoring and data logging capabilities. If you hook it up to a computer, you can control it from another computer in a different location.

The MCC-1 is designed to be the central hub for all major atmospheric and timed functions required in an automated growth environment. This unit can control temperature, humidity and Carbon dioxide enrichment.

The microprocessor based Plant Pro™ hydroponics controller from Solatel offers exact electronic timing for lighting, irrigation, ventilation, and CO2 dispensing. Accurate measurements from environmental sensors allow for perfect environmental control.

Lighting Timers
These diligent and hardworking timers from Green Air provide the most reliable lighting control. With their precision synchronous clock and high amp switching circuit, they're built to handle high load lighting equipment. Options include: temperature override (turns lights off if your room temp exceeds maximum levels; lights come back on when the area cools down), latching relay (disengages main contractor in event of a power failure) and an internal self-charging battery (capable of keeping time up to 90 hours during a power failure).

Industrial Timers
Industrial timers are durable and offer features that regular timers do not. Cycle timers are geared for irrigation or CO2 control. Time is broken into duration and frequency, allowing the you to have extremely precise interval times. Another industrial -rade timer we offer is the 24-hour Dual Timer, which is capable of handling up to two 600 watt lights or one 1000 watt light with accompanying pump or vent fan. The beauty of these timers is the flexibility they provide.These industrial timers encourage you to be innovative creating your gardening space.

Relays
Relays are used with environmental controllers to allow transfer of power to large equipment requiring high voltage or amperage service. The heavy amp load goes through the relay and not through the controller. Relays are integral in transferring high amperage power loads.