At first when I have designed my teardrop, I thought it was best to have only one window in the door to hav more wall surface to hang stuff and to eventually build cabinets. Problem is I don't have enough ventilation with only the roof vent since the door's window don't open. So, I made the uneasy decision to cutout the wall to install another window. This new window has a crank out bottom half and a screen to keep bugs out. I have bought it on ebay for 100$ + shipping + #\&§ UPS brokerage fees. I just need to make sure it will be completly sealed.
