I looked into split system A&#x2F;C when I moved to NYC. The gist is that attaching <i>anything</i> to outside of a &quot;historical&quot; building requires planning approval, complete with engineering drawings and a public hearing.<p>But hanging a window A&#x2F;C out into the street? Somehow this does not affect historicity and so no approval is required.<p>I&#x27;m vague on whether the rules apply to non-street facing installations (I live at the back of my building), but I don&#x27;t know if I can be bothered to spend the money to find out. So window A&#x2F;C it is.