Intake / Exhaust Question?

My cab has been around 78 but since it has started to warm up a little outside even with heat off has jumped to 82 even when I leave the cab door cracked a bit. I want to be able to close door completely. So I am looking into getting a carbon filter with a 200 cfm fan in a 4x3x6 growroom. Is this adequate size for the space? Right now I have my intake low on one side of cab and exhaust high on the opposite side of cab with no exhaust fan hooked up yet. Just a duct running from my light venting back into the bedroom so then it just recirculates that warm air back into the cab. So would it benefit me more to drill a hole in my floor since its a mobile home and bring my intake in from there or to cut a whole and exhaust to under the mobile home? I would love to have an attic to vent into but options are limited.

Yeah - you got the right idea... If you are able to use the intake from under the home, that would be choice. Use a filter of some sort on the intake - HEPA grade if you can afford it. Your 4x3x6 area is 72 sq ft - so a 200 CFM should work nicely; exchanging the air in your grow a couple times a minute or more - as long as you don't impart too much drag from the duct work and filter. Exhaust out the roof of the home. Your exhaust will be filtered through your carbon filter. This way you are working with physics - warm air naturally rises... if you bring in fresh air from the cooler air below your home, and then naturally exhaust warmer, stale, air on upwards and out, you should effectively be able to drop the temps in your grow to within 5 degrees of your intake temps (the temp below your house).

I have used this technique several times in the past with much success. In the pic below, you can see how I am using a a 6" fan to bring in cool air from under the house to route into the veg room (not for the clone closet pictured). After circulating throughout the veg room, the air was exhausted through a filter and 8" fan mounted on the ceiling. You can use the same principal but skip the intake fan. Your single exhaust fan will create enough negative pressure to draw air in passively from your intake port. Be sure the intake port is filtered, but free flowing.

Thanks Lion I appreciate it. I think what I may try to do is to cut into my air duct below and put a cap the other end and a good screen on my intake side so no critters get inside. Then take my vent off inside on my floor and hook my duct to it somehow and bring it into my cabinet. I do not have the option of venting out of my roof here since I do not own. So my only option I can think of is to vent back into the bedroom and as long as I have that cool fresh air coming in then hopefully i'll be able to keep it cooler. As long as I can splice into the air duct it should be fine but it doesn't have a fan pushing or pulling it in until I get my exhaust fan ordered and installed.

Yeah Blu - sounds like a plan. Yeah - probably won't get the results you want until the fan arrives, but you can have it all ready and waiting for her! haha

Good luck. Keep it cool!