Our planet is dynamic not stagnant. Low pressure and high pressure systems collide and create wind. The wind can dry or moisten an environment which in turn can open or close the stomata on the surface of leaves, slowing the plants growth. If the humidity is too low the plant will slow down in its growth. If the humidity is too high bacteria and fungi can flourish.
In an indoor grow room fans are an absolute must. Besides lighting it is the most important consideration when setting up. Fans help emulate our planets dynamic systems keeping the temperature and humidity at a constant level in the grow room.
Carbon dioxide is just as important as any other element presented to a plant. Even if nitrogen, hydrogen and carbon are present and plentiful at the root, if there is not sufficient air flow there is an important missing link in the plants construction material. Using a fan will keep the plant breathing, metabolizing and growing at an optimum rate.
There are many different types of fans on the market today. Everything from small computer fans and squirrel cage fans, to top of the line vortex fans that will do different jobs in different situations. In situations where there is a high intensity discharge light (more than 400 watts burning) a small fan under 250 or 300 CFM (cubic feet per minute) will not do the job. In most case a vortex fan is the best choice, simply because of the volume of air these fans can push. The way the blades in these fans are configured are like jet engines rather than propeller blades. They are manufactured to drag air a long way from the basement to the rooftop in houses and commercial buildings. When purchasing a fan it is a good idea to put your money toward a good strong fan that is even a little more CFM than what you need, in case you are dragging air a long way or through something like a can filter or air cooled shades.
A general rule of thumb is if you have 400 watts of light you should have at least 400 CFM per bulb and if you have 600 to 1000 watts you should have 600 CFM per bulb. Another way to calculate volume of air exchange in a room is mathematically. Knowing the length, width and height of the room, you simply multiply these 3 numbers to find the proper fan that will exchange your air in one minute. For example, a 10x10x8 foot room is 800 cubic feet so your fan must be at least 800 CFM in order to achieve the one minute exchange. Very small areas can use smaller fans, but a small area can get heat build up very quickly and will still need good steady air flow. In cases where heat build up is a problem (even in large rooms) an intake fan pushing the same volume of air as the outtake fan can be installed down low in the opposing wall to help cool the air faster and make the air tumble through the garden. An oscillating fan blowing gently across the leaves in tandem with intake and outtake fans will keep the plants fed well with carbon dioxide and will make the plants stems stronger at the cellular level. If heat or cold is a problem all fans can be hooked up to dimmer switches or heating and cooling thermostats to keep the room at the proper temperature parameters.
All fans run on a curve and there is a point at which the fan runs most efficient. Every piece of equipment placed in front or behind the fan has a negative effect on the performance of the fan.
- Equipment like louver or butterfly dampers will impede the progression of air to a degree.
- The ducting and specific type of ducting will also affect air flow. Straight, smooth galvanized ducting will let air flow better than plastic ducting with ribs. The ribs create small baffles along its length and static pressure will build up in the duct work.
- Length of pipe is another important consideration. The shortest and most straight forward span of pipe or ducting should be used for the most efficient air flow. According to heating and cooling duct work contractors, every 45 degree bend adds 10 feet to the length of duct and a 90 degree bend is something that will start to work against the fan; the air will actually find its way back to the fan and leak out into the room.
- A fan should always be set up level. Hang the fan straight up and down vertically or perfectly horizontal. If you hang the fan off kilter the bearings will rub together unevenly and over time the fan will start to make unbearable sounds and in the worst case, will stop completely.
- By sealing all connections and air leaks with silicone or metalized ducting tape you will ensure complete air flow with no air escaping back into your room.
All these components in front or behind the fan should be taken into consideration when you are envisioning your room.
Air flow and air movement are very important in the garden. When you are shopping for a fan you are going to get what you pay for. Purchasing a fan too small or of inferior quality spells trouble. Don’t be afraid to spend the money on a good fan and you won’t spend more money trying two or three time with lesser fans. It’s something like buying a $700 fishing rod and putting a $3 reel on it. Having a good quality, proper sized fan should be one the strongest links in the chain.
Getting started
- Decide where you are going to place the fan in your room. High up in a corner is best for expelling hot air.
- Get the proper size fan to change the air in your room a couple times a minute.
- A 10x10x8 room is 800 cubic feet. An 800 CFM fan is necessary here, at a minimum.
- Make sure the fan is level horizontally or vertically.
- Make sure the length of your ducting is the most straight forward and the shortest span possible.
- Purchase a fan that is more powerful than you need in case you add carbon filters or air cooled shades.
- The intake fan should match the outtake fan.
- Seal all connections with silicone or metalized duct tape.
- Use an oscillating fan for mixing air and creating a gentle breeze across the plants leaves
- Spend the money on a good quality brand name fan once.
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