Back for more air

By Scott Misener

Buying an exhaust fan is only half the battle. Now you've got to set it up right. The concept of ventilation is easy. The exhaust fan needs to pull air off the ceiling and move it out of your gardening area. This is crucial because hot air rises and sits like a heavy blanket on the ceiling. Now you need to think about the intake. The intake is your fresh air source. There are a couple different ways you can approach the intake. Ideally, try to set up a passive air intake. Passive air intake is a term that refers to the path of least resistance. The path air will always take. Did I lose you? Think of it this way. Exhaust fans move a large volume of focused air out of the room. So that means that air need to come in from somewhere. Air will always pass through an open space, or a path of least resistance, over an obstructed or filtered path. So if you have or can install a vent in the wall at floor level of your garden area and turn your exhaust fan, you and your plants can breath easy because fresh air will come pouring into your garden simply by the vacuum created. A window you can slide open may also be used, but put some thought in its position.

The points of exhaust and entry are crucial. I talk to a lot of people who have heat problems attributed only to the fact that they have their exhaust sitting on the floor. It's getting hot because they are not venting the room. Exhaust needs to pull hot air off the ceiling. The intake should be at the exact opposite point of the garden area. The idea is that fresh air is cool. When it comes pouring in through the vent it will move along the floor. As soon as the light shines through the fresh air, the once cool air will be heated, causing the air to rise up through the plants in route to the exhaust on the ceiling opposite from where it came in. This way, the fresh air travels the full length of the room before it is exhausted. And by moving up through the plant's canopy, the plant will have fresh air where it needs it the most, at the stomata openings on the underside of the leaves. Now you see it makes no sense to have the exhaust sitting on the floor. The fresh air will just get sucked off the floor and you will have a compounded heat problem as that blanket of hot air just gets thicker in the room and your poor plants will suffer. Another common mistake is having your intake and outtake right next to each other. You can see what is going to happen. Air will be pulled in and quickly sucked right out without dispersing throughout the room. If your ventilation is not working efficiently and your plants suffer, you can count on cutting your plant's production in half. Ventilation is that important! I cannot stress that enough.

Now, if you have a vent or window close to the floor and your area is airtight you can enjoy the luxury of one less fan for intake. That means less electricity being used and less noise from a rattling fan. One small detail I failed to mention, the room has to be airtight. If you have large gaps or holes in the walls or openings to rafters leading to an attic above, this method will not work. Since air is pulled through the path of least resistance, as we just discussed earlier, you would be pulling stale air from another part of your house. And if that stale air is coming from a hot attic or a crawlspace that has never seen fresh air, your plants will suffer. Small cracks and seams can be patched with that miracle product known as foam in a can. If all these factors are working against you, you need to bring air in with another fan. Blowers, commonly referred to as squirrel fans, offer an inexpensive, cost effective way to move air. You don't necessarily have to match the CFM of the intake with your high-powered exhaust. You want to come close, but put the more powerful fan moving the air out. The exhaust fan will actually help bring air in through the smaller fan with the vacuum it creates.

Upon hearing the term ventilation, many people wince and immediately disregard the idea of an extensive ventilation system because that means you have to cut holes and alter the property. Nobody wants to cut 8 to 12 inch holes in their ceiling. Not to mention that landlords will go crazy and you probably won't see anything that resembles your security deposit ever again. There are easy solutions to these problems. Almost every room I've been in has light fixtures on the ceiling. Just remove the fixture and run ducting through the hole already there. Another method is to take off the door to the garden and replace it with a cheap mock door that you are not afraid to cut holes in. Just cut two holes in the bottom of the door, one for intake and one for exhaust, and push and pull air through those holes.

Bottom line is that you need to know, understand, and believe in your ventilation system. You're plants will thank you with abundant fruits and vegetables. Come back next week when we talk more about air movement and air purification. The best is yet to come! Love your plants!

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