So I'm going to be pulling air from a window now. The problem is I run my lights at night, so any day time liht that reflects down through the duct hole could be a big issue. Is there any way to make the inside of the duct hole light proof?
Yes, build a light trap. Make the venting with at least two bends of 90 [FONT="][/FONT][FONT="] and paint the inside of the venting flat black.[/FONT]
What he said.... Or you could buy insulated pipe... (I could only imagine the insane amount of frustration trying to paint the inside of ducting... I'm sure there must be an easy way to do it, but I'm fairly sure I would still f*** it up... )
The venting comes in pieces. Get a can or two of flat black spray paint, you should be able to completely cover the insides of the elbows, and at least the first foot inside of each piece of straight vent. A lot of venting comes flat (you make it into a tube shape on the job site), so easy access to paint the whole inside before assembly.
Wrap either side of the duck that is receiving light with a black t-shirt and puncture some small holes in it so it will breathe better. I also use the carbon filters from an under the sink compost holder bought at stop and shop. Its black 4" and also is way less expensive than an actual carbon filter setup.and also yes 2 90* bends will stop light from coming in, but it will also restrict your air flow. With a wood burning stove, you cannot have more than 2 90's or 4 45's because it reduces natural draft up to 40%.
^I don't care for that idea, this means you are trying to block light by also blocking airflow. And it's a duct, not a duck...
Let me be the devil's advocate here. Two 90* turns in a pipe using the same diameter WILL constrict airflow. Using a black t-shirt is a cheap, yet bad idea as you will constrict to much flow. I have seen many a baffle box designed to keep light out and in for that matter. Being that I have lived in a lot of southern states, hot, sunny states I have seen many ways to solve this problem. The best I have ever seen was also the most logical. SUNSCREENS. You can choose from about 6 different colrs including white and they block either 80% or 90% of ALL UV rays. Simply placing one of these at both ends of the duct will eliminate light from entering your grow chamber or escaping outside to your pesky neighbors. Depending on your current fan set up you may need to add a duct-booster fan to compensate for the air flow blocked by the screen, but then again, it's a screen, air moves through mine quite well.