I knew someone that had an HOA rule against window air conditioners. His solution was to keep the window-mount unit inside his bedroom, with the back end (that

I knew someone that had an HOA rule against window air conditioners. His solution was to keep the window-mount unit inside his bedroom, with the back end (that normally sticks outside the house) enclosed in a box. That box had an intake and exhaust fan, with flexible duct work that routed to a piece of plywood stuck up in the window. From the outside, you just see the screen with the plywood on the other side. But it worked about as effectively as if the whole unit was mounted in the window.