Ventilation Ideas

[gilly]

just after some info on ventilation and fans . i,ve positioned my outake fan at the top of my cupboard but im wondering where i should be putting the intake fan . does the fan have to be blowing directly onto the plants or as long as there is fresh air getting inside

[F420]

hey ya Gilly,

 

Mate have a search through the site theres been dozens of discussions on this matter.

 

But the breifs of it is that you dont need and inlet fan or an osc fan. As long as the air being drawn from passive vents at the bottom is causing the plants leaves to move a little bit. This helps to shake spent air from the plant and allows it acces to fresh air co2 etc.

 

heres a bit from www.hydrocentre.com, written by Scott.

he owns a hydro shop in the Gold coast and has over 13 years of hydro experiance.

 

Yes ventilation is like a black art, not as much facts and designs, but more looking and feeling it out. Here are some guidelines

 

1. Inlet fan and exhaust fan. Make sure you have air flowing into and out of your system. Make sure your fans suck in as much air as the other is blowing out, or you will find the rated air movement capabilities are reduced.

 

2. Air Quantity. Carbon Dioxide is what they breathe. So work off 10 air-changes in the room minimum to keep them breathing - even if using air-conditioners. More air-changes will be required to keep temperature under control.

 

You work this out by fan capacity and room size. If your room is 1m x 1m x 2meter, this would be 1x1x2=2 cubic meters. If a fan is rated at 600 cubic meters per hour. this would remove the air from a 2 cubic meter room 300 times every hour.

 

3. Temperature control.

 

TOO HOT: If you are not using air-conditioning, and the air temperature is getting hotter than the ideal 25 degrees with the light on, then you will need to use more air ventiation to keep the room cool. Use 100 airchanges for a moderately warm room, and 200-400 airchanges to keep a hot room under control. The theory of this is that if the air comes in at 25 degrees and heats up to 30 degrees by the time it exits, then if the air is sped up, and changed twice as fast, then it should only heat up by half as much. It follows that if you double the air changes again, then it can only heat up half as much again, but it will never be cooler than the incoming air. If your incoming air is 35 degrees or something you will have to bring in air that is fresh, but cooler, from another room, window or anywhere cooler.

 

Remember cool air sinks, hot air rises. Remove hot air up near the ceiling, and draw in cool air near the floor. It helps also that Carbon Dioxide sinks to the floor too, and is best (most densely concentrated) the lower you go to the floor.

 

TOO COLD: So if the air outside is cool, say 10 degrees, then the fans should only be on minimal because the light will only raise the temperature by 5 to10 degrees. So some people might have their fans on a timer during the night or during winter to keep the room from getting to cold, to adjust the fan to only bring in the minimum of 10-30 air-changes during that period. So if a fan is 4 times what you need, try 15 minutes per hour on a timer to refresh the room without cooling it down and freezing the plants. It is true that plants can survive cold without adjusting fan cycles, but generally they don't look too healthy.

 

Remember that if the room is not ventilated at all during the artificial night, mould occurs all over the plants. This is due to the lights going off, and the temperature dropping enough that moisture from the air begins to cool. This cool moist air is high humidity, and is what mould loves, If the ventilation continues the moist air is drawn out and the temperature equalizes at a more suitable humidity. The first hour is the most critical to remove this moist air, then less important through the rest of the night.

 

4. Circulation. Imagine you are a little breeze of air, you get thrust into a room, bashed up against some plants. You want to go out the exhaust fan. Because you are lazy, you take the easiest route. Not through the leaves, but over the plants and around them, then out the exhaust. This will take the heat out, but leave the plants still gasping for breath. You notice plants on the outside doing better than the centre. This is due to the plants not getting fresh carbon dioxide to breathe. Carbon Dioxide will improve your growth and yields more than any additive, so never take it for granted. Use a oscillating pedestal fan to blow the air into the leaves of all the plants. No need to blow them over, but get air to the plants.

 

5. Dead spots - As in circulation, if there are areas where the plants are not performing, they may be in a dead spot where more air is required. Aim pedestal fans at these areas.

 

6. Windows and insulation. It never ceases to amaze me that people take no notice of a room before they set it up. It may face the midday sun, and heat up like an oven. This is not a good room. Is the house insulated. If you grow in a room that is tiled it may be cooler than a carpeted room. Take these things into account, and adjust the ventilation accordingly. Maybe reconsider that hot room.