How should I vent out this window ?

[Southsidestl]

I’m trying to figure out how to vent my outtake through this window. Not possible to vent anywhere else in the room & this window is the best place, but I have no clue on how to create a air tight seal on this window using a standard duct

[Poppa]

I will need some more information in order to help you. First is this something you will need to remove and reinstall regularly, or will you install at start of a grow and remove then replace with the windows sash once grows complete. Secondly are you going to black out the windows which in turn would mean what ever is inserted would in turn need to be light tight. Looking at your picture I would estimate your working with approximately a 5" x 14" opening. In the picture I added the register boxes are 4" x 10" I made a 1/4" cut in each corner and then bent all 4 sides to make a mounting flange and used silicon and 1/2" wood or sheet metal screws to mount to the board that makes up face of my window insert. I would prefer any measurements you provide while working through this be in inches as I haven't studied or had to use the metric system with any regularity in 40+ years.

[Ckbrew]

Remove the tilt out window and screen. Make a filler panel to fit in the opening. Cut holes in filler panel sized to your duct work.

I would clean up that black mold on the window frame while you were in there working on things.

[Poppa]

I personally would leave the screen in place since it would be outside or in front of opening air is exiting through it will help keep insects from entering well the larger ones at least

[Ckbrew]

Valid point unless you are using filters on the individual ducts.