How to vent and keep light proof?

**demonicus** · 06-28-2008, 12:15 AM

I'm running into the problem where my temperature in the box is rising to 80 degrees. So obviously I need some ventilation. I'm thinking of jigsawing a hole in the back and putting an exhaust fan in with intake holes in the front. My question is this: How the hell do you keep light from coming in and still vent?

**dr.greenthumb85** · 06-28-2008, 12:25 AM

place the vent hole near the top of the box, use a piece of ducting to create a tunnel and tape some black plastic big enough to cover the hole but only tape the top part so that the air still gets out but when fan turns off the black plastic falls back over the opening. aka light trap.

**demonicus** · 06-28-2008, 12:29 AM

Ah, I think I understand. So only run it during the "daytime" hours, as it doesn't need to vent at night.

What about the intake holes?

**dr.greenthumb85** · 06-28-2008, 12:33 AM

same thing but the hole needs to be near the bottom and the plastic needs to be on the inside.

**T9X** · 06-28-2008, 12:35 AM

your going to want twice the as much intake as exhaust. for example if you have a 3 inch exhaust you will want 2 3 inch intakes

**bohicular** · 07-24-2010, 09:15 PM

Originally Posted by T9X

your going to want twice the as much intake as exhaust. for example if you have a 3 inch exhaust you will want 2 3 inch intakes

As far as I know, its the opposite: more exhaust than intake. If not, you'll be creating a positive pressure, which will push air out of any crack or opening (not the exhaust), which is bad if you want to control smell. Could be wrong, but i'm pretty sure...

i'd like to know if you solved the problem, and kept good airflow. I'm working on light traps for my intakes now

**Nocturn3** · 07-24-2010, 10:04 PM

Originally Posted by demonicus

Ah, I think I understand. So only run it during the "daytime" hours, as it doesn't need to vent at night.

You should run your fans 24/7 or humidity will rise, and mold may become a problem. For light proofing intake and exhaust, people use different methods, depending on their setups. Some examples are: s-bends in ducting, louvred grills, pvc tubes with bends, a series of baffles, carbon sheets etc. There are many ways to do this. Just remember that light travels in straight lines, and bounces off light-colored surfaces.

Originally Posted by bohicular

As far as I know, its the opposite: more exhaust than intake. If not, you'll be creating a positive pressure, which will push air out of any crack or opening (not the exhaust), which is bad if you want to control smell. Could be wrong, but i'm pretty sure...

If using active intakes (ie: a fan) then the intake should be slightly smaller (or weaker) than the extraction, in order to achieve negative pressure. If using passive intakes (ie: no fan, just holes), the intake area should be several times larger that the extraction, in order to avoid stressing the exhaust fan. Exactly how large will depend how powerful the exhuast fan is.