I live in AZ and, while the central air units are on the N (NW) side of the house, once the sun does get around there (which is also the hottest part of the day), the units get baked. I can only assume this causes efficiency to drop. For this reason (as well as aesthetics and noise control) I would like to provide the unts some shade by growing an ivy or vine over them. Obviously I would build a mesh frame upon which the plant would grow. My question is 1. is this an acceptable solution, 2. if so, what clearance is required between the A/C unit and the plant frame, 3. if not, suggestions?