Hi all, ive built a small box 2ft x 2ft x 3ft. Got 8 23w cfls, 4 on an adjustable plate above and the other 4 scattered around the sides . Got a 4inch inline fan and carbon filter on the ceiling of the box and venting out the roof. The fan is rated for 105m3/h which i think converts into 61.8cfm. My problem is i dont know how big i need to make my intake hole for a passive intake. Iam planning on using angle alluminium stacked with spacers to make a light proof vent just dont know what dimensions are needed. Reading online has just confused me because some say it needs to be smaller others say it needs be slightly bigger than exhaust some say 5x size of exhaust. Also will i need a small fan on the plants or will the air being sucked into through the passive vent be enough to strengthen the plants.theres only going to be one or 2 in this small box.
twice the size of the outtake. However I assume you will be using some kind of light baffle so you need to increase the size of your passive intake(s). The amount will depend on the number and angle of turns on your light baffle.
Iam using 90 angle aluminum stacked with spacers to make a light proof vent. Il upload a pic in a min. The actual part that the air goes through is a fraction of the overall size of the vent.
Hard for me to tell how the air flows. Everytime you make air bend 90deg then you need to increase the intake hole by 25%. 180deg increase by 50%. The increase is proportionate to the bend to a total of 360deg. Therefore 360deg worth of turns means doubling the intake size. 4inch outtake with the following amount of bends 0 bends = 8 inch intake 90 deg = 10 inch intake 180 deg = 12 inch intake. And so on and so on. Btw i started with a light baffle that i still have but installed additional intakes using black upvc pipes. Can get fresh air to different parts of room then. Also easy to cap them off if you overdo it.
The air flows through each layer between the wooden spacers, i was planning on using 4 of these 2 on the left 2 on the right but liking the idea of the upvc piping u mentioned.
Its cheap, easy to cut and install. Just caulk around the hole and tape up to ensure no light leaks. I added some diamateceous earth in the pipes to ward off pests. Next grow I will remove my baffle and install a network of pipes to bring fresh air throughout the underneath of the canopy.
Cheers, went with a cardboard baffle for now whilemi figure out where i want to run the upvc pipes. Should you be able to feel air rushing into the baffle from outside the room, i can feel a slight cool breeze through my fingers but doesnt feel like much.
Ive since painted the inside with white light and space paint added 3 more lights to the walls and put an insulated floor in so its not sat on concrete.