Flex vent is the stuff that is connected to your clothes dryer. You can get it at Lowe's/HD. Get the vent and some flat black paint and paitn up inside the flex tube as far as you can, then put it thru the wall near the top and hang it down close to the bottom on the inside - so you'll be going flex vent -> fan -> flex vent and that should keep out the light. Don't put a cover over your intake, it'll stop the air flow. If light is getting in, put on another elbow.

PC :smokin: