Design Help Needed

First off let me give you a little history on the current set up. Room is 3.5'x7.5'x7' all walls are cement, no windows or vents. The only way to get any air was to cut holes in the door, I cut a hole on the top for exhaust and a hole on the bottom for passive intake sucking air from main room w/ ambient temps of 66 degrees. With my first time I made a temporary wall and split the room in half (3.5'x3.5'x7'). I was using 1 400 light and the temps were staying 72-77 degrees. Now I'm using 2 400 watt lights (my buddy gave me one) and the temps are reaching 82 degrees or so during the 3rd week of veg. Neither of the reflectors are able to be hooked up to the exhaust fan, so the exhaust is just sucking air from the room not the lamps directly. My concern is that temps are getting too hot and might only get hotter when switching to hps for flower and with summer coming up and all. So my question(s) are 1. Are temps in the lower/mid 80's with no co2 added too hot? 2. Would it be better to just say buy a new ballast and reflector that I can exhaust more properly? 3. Would adding co2 take care of the temp issue?
Any help would be greatly appreciated, thanks in advance.

i think you will be fine at mid 80's, if it does get too hot, put a fan blowing up forcing the hot air up, out the exhaust.

Low 80's wont hurt your plants! think of all the outdoor growers in california!. you said you cut a hole in the top and a hole in the bottom for air. with the fan blowing out of the top you need and intake fan, a really large hole or more holes. even though you have solid walls it is easier to explain with a tent setup. When I first set up my tent I did not have an intake fan. I was using 6in ducting and a 400cfm fan. i turned it on and the tent looked like it was being vacuum sealed. My intake fan wasn't in yet so I stuck 4 pieces of 6inch ducting (like cutting 4 6inch holes) in, turned on the fan and it still was sucking the walls in but not as much. the fan blowing out was only blowing through 1 piece of 6in ducting. So with having an exhaust fan and no intake fan you are creating negative pressure in the grow room and putting a strain on the fan. so if you get an intake fan or add more intake holes you will get more air flow and cool the room a bit more!

What would be a good size fan for a room of that size? my current fan is only 95 cfm because my room was roughly half the size. I was thinking of maybe upgrading that to a 6" inline and using my old was an intake fan. Not sure if the added gain would be worth the extra $.

yes it would be worth it. you need good air movement! and if you go with a 400 cfm or above fan you might still need more of an intake than that!

killer chronix said:

What would be a good size fan for a room of that size? my current fan is only 95 cfm because my room was roughly half the size. I was thinking of maybe upgrading that to a 6" inline and using my old was an intake fan. Not sure if the added gain would be worth the extra $.

Click to expand...

calculate the cubic feet of your room...3.5feet x 3.5 feet x 7 feet= 85.75 feet
you want about 2-3 complete cycles of air being transferred per minute
160-240 cfm(cubic feet/minute) fan would be the very least you would wanna go as far as exhaust
for intake passive is good but during veg ive come to find out that having some fresh air pumped in will raise humidity a few notches, i run intakes during veg and turn them off in flower

hope this helps, +reps are always welcome,lol

You are very lucky to have 66 F air to draw from. Draw from it! I would use an 8" inline exhause fan in the upper hole, and run an 8" duct with a booster fan from the lower hole to the far side of the room (booster fans are cheap). This would effectively position your air intake on the other side of the room from your exhaust. By moving 750cfm (8"inline), you should be able to run a couple 1000 watt lights and still keep the room well under 80. I have found that over 80 F the buds tend to get a little fluffy. When the lights go off your temp should be the same as the intake air (66 F), which is perfect night time temp. You have the right stuff to get your atmosphere dead on...might as well use it.


https://www.rollitup.org/indoor-growing/407048-20-000-watt-medical-grow.html

Thanks for the info!! Plus repped. Going to my local store tomorrow to see what they've got in stock for exhaust fans.

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