passive ventilation system help!!

ok so heres the dilemma i just installed my exhaust system with carbon filter. heres the problem my temps ar getting too high on my test run i ran the fan on full blast for about 30 mins with my 600 watter temps went from 77 to 81 in 30 minutes im sure it wouldve stopped climbing at some point.i have a wing reflector i figured it would be better and a little cheaper to air cool the room i dont have a fan for intake but my exhaust fan creates a low pressure in the room and sucks air in from wherever it can ie the door cracks and the floor vent for the centeral air.im wondering if i can just stagger holes in my wall leading to another room put a vent cover over them so they look normal i could put one hole near the floor in the grow room and one high in the opposite room. anyone have any input??

just ran a test again and the temp got to 85 and was climbing even had the door open

A way I found that could help vent the HEAT from the room, is to run the exhaust duct close to the light. I also use an open reflector, and when I moved my exhaust from the corner of my tent to the light (about 3 ft away) the temps dropped dramatically.

Or maybe you don't have enough negative pressure to really evacuate the room air. How large is the room? what is the rating on the fan?

bignam said:

just ran a test again and the temp got to 85 and was climbing even had the door open

Click to expand...

Prob because you're venting into the same room... Plus whats the temp of the air that's being pulled into the room?

my room is 392 cf and the fan is rated at 487 cfm and i have a 400 cfm phresh filter

im venting directly out my window and my filter is right next to the light also

temp outside is around 76

is your carbon filter mounted to the ceiling or on the floor?

Fan seems adequate IMO...


Are there any fans moving the air in the room?
Are there any plants?

the filter is mounted to the ceiling

i have one big fan like a bedroom fan those round ones you get at walmart and no plants yet its a new construction

heres a pic

how long is the exhaust duct?
if its realy long you might need a booster fan. putting an intake would def help esp if you add a fan to that. if its already hooked up to the central air you might be able to figure out a way to use that opening. if its 77f ambient it's prob going to be hard to keep it cool in there you might have to run thge lights at night or use ac.

Yes you are correct you need to do excactly as you are planning ,( Off set) 2 stamped face grills on each side of wall , just make sure you are in between the same bay ( studs ) and give the off set (lower higher) 18 '' between the 2 holes so no light leaks through. this will help a lot . remember measure twice cut once = no mistakes

My ducting is very short ite filter than about a foot of ducting than the fan than about 2 feet to the vent i could crank the ac up but i didnt want to use that much electricity i was going to use an ac on a day/night temp controller but my budget for the room ran out lol! I do have a non vented hood with glass im wondering if i should just use that instead of the eing but its old and the reflector in it prob isnt as good now..i really think that fan is working too hard tho because i dont have a real intake. But also i had the door wide open and the temp kept climbing....

I will probably end up doing that the way i pictured it in my head makes alot of sense..i just have to figure what size hole to cut good thing i have measuring tape lol

what you need for 400 cfm is either 10x10 or 12x8 Stamped face grills (flat grill) cheep , home depot , lowes or local hvac supply house.

Awsome and lowes is my friend lol!

I hope you still got some money in your budget, you are not lowering your temps without more gear. You will never get your temps any lower than 5 degrees above the ambient temp withut AC.

1. Air ccooled hood. You need to get that heat from your bulb straight out ya grow area.

2. higher CFM fan, 720 or better. To show the effects of higher CFM, uncouple your filter. This will increase your actual CFM as no resistance pulling air through filter. You should see a temperature drop.

3. 2nd venting rig, all you will need is a fan and ducting, no sencond filter. Run a straight through vent for your lights (no filter, pull clean air in to cool light, clean air out) and a secondary system to scrub the grow room air.

4. not a huge effect but get your ballast out of grow area.

If you are expecting your ambient temps to increase, yr gonna need all of the above and probably an AC.