I'm setting up a small grow tent--2x3x5. That's only 30 square feet. Do I really need a high velocity fan? Would one these cheapo inline duct fans that cost only around $20 be enough? I'm going to connect it to a 400w cool tube HPS. Am I right in thinking that duct fan might be enough to provide sufficient ventilation but might not have the power to force the air through a charcoal filter? Also, I'm worried about temperature. I'm setting this up in the basement, and winter is coming. If my ventilation is really effective in removing the heat from the HPS light, maybe the tent will end up being too cool. What's the best way to cheaply keep the tent at the right temperature? A heat mat? I know they're for germination, seedlings and roots, but in a small tent would that work to keep the whole thing at the right temperature? Any other suggestions as to how to keep the tent warm? Thanks in advance.
IMO get a good inline Vortex type of fan and a speed control. If you have to run the fan at full speed, you need a bigger fan. If your worrying about getting cold, redistribute the hot air from the lamp. You do not want to force air into the filter, but draw air into it. Make your fan the last thing in the chain.
Also, I treat the heat and odor (stink) as separate issues and with each having their own fan. Get the air for cooling your lamp from a different source other then your grow area. Then you can run a small fan to vent the stink so you don't overwork your filter. You will almost have to go this route anyway if you add CO2 down the road.
Thanks for the tip. I see your point, but wouldn't that mean investing and finding room for two fans, two filters and two lenghts of hose in an rather small space?
I stuck my fans in the attic with the stink vented through the roof. I just dump the heat from the lamp in the attic. You don't need to filter the air to or from the lamp. I didn't say it was easy either!