For dwellings containing four or more dwelling units, there shall be provided on the same lot garage space or garage space and paved off-street parking space sufficient for the parking at one time of not less than 1 1/2 times, nor more than 2 1/2 times, as many passenger vehicles as there are dwelling units on the lot, provided that such parking facilities shall include an enclosed garage or garages, sufficient in area for the parking at one time of not less than as many passenger vehicles as there are dwelling units on the lot. Wherever space is provided for the parking of four or more vehicles in the open, except for points of ingress or egress, such spaces shall be screened by an opaque fence, wall or evergreen hedge to such height and in such places as shall be approved by the Planning Commission. No parking space, whether required or discretionary, shall be located in any front yard or within five feet of any side or rear lot line. The parking of motor vehicles within 15 feet of any wall or portion thereof of a building containing four or more dwelling units, which wall contains legal windows (other than a legal bathroom or kitchen window) with a sill height of less than eight feet above the level of said parking space, is prohibited.