If your home doesn’t have Cold Air Return Vents then it’s probably because it doesn’t need them and ventilation was a consideration during the construction. Either that or your home desperately needs some kind or air return vent even though it doesn’t have any.  Sadly, there is a lot of real estate which fit into this later category and many houses are rife with damaging mildew and mildew spores and the occupants don’t even know it.  People’s health deteriorates, they may find themselves constantly lethargic, and just lacking in any real energy. All too often, people don’t identify the cause as being constantly damp home and just think that the stress of everyday life is taking its toll. If this is you, then it might be a good idea to get an expert to come and check your home for rot and fungus.