I used a Doran Darkroom Light Tight Fan For Rooms ($130 Adorama), that I configured to be my exhaust fan. I was able to pull out the basement window and use a sheet of plywood that I got at a garage sale for $1, it has a neat Native American motif on it that I had always wanted to hang, found a great spot for it. Then used HVAC ducting ($50) to create the below. Don't mind the pink walls, the house came that way and have yet to paint....