In my building I require that any tenants installing air conditioners install a portable air conditioner rather than a window unit. That's because I've had tenants drive screws into window sills and PVC window frames in order to get the window unit tilted properly to drain to the outside.
In my view, the portable units have the advantage that you can fashion your baffle to fit more tightly over a window than you can with a window unit. That's because you merely have to fit a duct into a baffle of your own design, so you have complete freedom to design that baffle to be both leak proof, and unlikely to damage the landlord's property when it's installed and removed.
Also, residential walls are much thinner than the 18 inch thick concrete block/ brick veneer walls on an apartment block, so balancing an 80 pound air conditioner on a 4 or 5 inch thick wall is just a problematic proposition right from the get go. If a cat jumps onto the top of the air conditioner, you could have an 80 pound air conditioner falling onto unsuspecting pedestrians below, and that might cause a stir.
The portable units are a little more expensive, but they eliminate that balancing act and the compulsion to drive screws into the window frames and window sills to get a window unit that's as heavy as sin oriented properly in the window opening.
Last edited by Nestor_Kelebay; 07-12-2010 at 10:02 AM.