Screen? The screen is removed to install a window a/c unit. What would you do otherwise? Cut a hole in the screen and set the unit through it? Surely not!

Xamius,

Typically one needs to lay a piece of wood on the window outsie the sill on the sloped section so as to elevate the inside edge of the unit to a) clear the storm window frame and b) create the correct slope so that the unit drains to the outside of the house. The wooden piece might typically be a 2"X4".

This post was edited by saltidawg on Wed, May 8, 13 at 7:55

I think the OP is saying the bottom frame of the storm window is 1.5 inches higher than the window sill.

You can cut a piece of lumber (2x4 or 2X6) and place it on the window sill. The AC unit should have a slight tilt to the outside in order for the condensate to drain. If this is going to be a permanent installation you can nail or screw the lumber to the window frame. Otherwise you could install L brackets with screws at each end so it can be removed at the end of the season.

Block the unit up higher at the window sill to clear the screen frame.

This is also a common problem with older 'triple track' storm and screen systems.