On UK cars, the top connection on the air filter housing is for cold air and there should be a pipe leading to a small grille beside the radiator. You definately should have a cold air feed from somewhere. Maybe one of the Greek or Cypriot members can say how this changes with A/C fitted.
The lower connection is for warm air and originally went a sheet metal scoop type thing which clips around the exhaust pipes. These have nearly always rusted and fallen off!
There should be a plastic thermostatic valve flap which selects which intake the engine should use but people often take it out.
If you climate drops much below zero centigrade in winter then a warm air pipe is a good idea. If not, forget it and have 2 cold air intakes.