Open windows are going to give you a horrible dust problem that you'll probably never conquer.

My d/r uses a regular bathroom exhaust fan with a long black hose to the outside vent, curled around so it keeps out extraneous light.

The air intake is through a filtering system built into the wall, with the air intake outside the d/r near the ceiling and the d/r vent near the floor. The wall interior is painted flat black.

- Leigh