Hi, at family house a new Friedrich CP10F10 was installed through the wall for the enclosed porch. (regular AC unit, not a minisplit). a metal cover was also installed and it occurred to us afterwards to ask whether there was a potential problem with humidity building up etc. (I'd think there would be some ventilation towards the inside of the house.)
Also, many people also put a fabric or plastic cover on the inside of the unit as well. Are both covers recommended? obviously with the outside cover there should be minimal drafts inwards, but cold could also be conducted inwards, hence the inside cover.