I've been building out new rooms, and came up with some solutions for large light proof vents in confined spaces. This is no small task, as light leaks cause plants to hermie and your yields will suffer, and also passive air intake needs to be bigger than the exit vent. Some say half again as large, some say 200-300% larger for the intake. Either way, you want a passive intake vent large enough to almost eliminate negative pressure in the room. You want slight negative pressure, just enough to keep the stink flowing in one direction - toward your filter. More than that and you are stressing your fan and reducing it's cooling efficiency. Here's what I did. In the veg room I used a small space away from the main growing area and boxed it in, creating a dark little maze for the air to travel through with baffles to block the light. I have a 6" duct pulling air out of the veg room, so I made the intake 13" X 8". Should be plenty big. After framing a little 13" X 8" door I lined the box with plywood, then covered with black Panda. I laid out where the baffles would go, marked with black tape on the concrete. Light travels in a straight line. It does not bend (typically). I was careful to make sure that at each turn there was a full 8" width so there are no pinch points reducing my actual air flow, and that the baffles extended far enough to block the light. Then I painted the underside of the shelving boards and the baffles flat black, and put it all together. Last I painted the floor black and taped up all the seams inside with black duct tape. I caulked the bottoms of the baffles, and put an outside cap on sealed with weatherstripping. After finding and sealing a few missed light leaks, the vent works perfectly. I can have the 1000W MH blazing away in there and not the least bit of light gets out. For the bloom room, I borrowed an idea from dxe and simply curled some 6" flex duct into a pigtail and tucked it into a bucket. Works pretty good, though the twist is horribly inefficient, reducing air flow by 30-50%. So I made two of them, though I don't have the room for both ATM. This one works OK. The ducting actually has a million pinprick light leaks that look like stars up close. THis causes a very faint but acceptable light leak. This is a temp solution until I make something better.
Just a thought on the ducting in a bucket. Instead of curling the ducting in the bucket, why not have a piece of ducting out the side as shown, but instead of curling it in the bucket, which as you say is very inefficient, use the lid for the bucket and have a 2nd piece of ducting cut into the lid? Just the 2 small pieces with nothing curled inside. This would get rid of the extra ducting in the bucket. And would still be air and light tight. In my mind I think this would be more efficient for moving the air through. If you were using the bucket on the exhaust side you could put your air scrubber inside the bucket. Does that make sense? It's early and I haven't smoked in a while. Peace....
if you put a 90 degree curve in the ducting into the top of the bucket and then have another, separate 90 degree ducting out of the top (not connected to each other in the bucket) you get a light tight, but very efficient passive intake.
i don't think that would work. What inside the bucket would block the light? Just a black space isn't enough. If you look inside and can see any part of the interior that can also be seen from the other side you will see light.
Skuzz you still have 2 90 degree bends in the vent. I just put them in the bucket. You've got the bends outside the bucket.
Interesting. Good point about the "efficiency" of intakes. I mean, you hear that in venting hoods you loose X% of the the cfm a fan produces for every 90 degree bend. I just always assumed the same was true for the air intake into the room as well. But you are quite correct that the room is not sealed, and despite my late night bong-and-duct-tape sessions, I will never get the room truly airtight. But I'm gonna try! I'm gonna go experiment with it for a while. Report forthcoming.
