The facade of commercial, industrial, governmental, institutional, and recreational buildings which face upon a street right-of-way shall be finished with an aesthetically pleasing material. A minimum of 30% of a facade facing and existing or future street shall be finished with brick, wood, fieldstone, decorative masonry material, decorative glass panels, or decorative precast concrete panels, except where the building style requires a different material. Attractive aluminum or vinyl siding which has the appearance of wood siding, a "brushed" surface or other compatible attractive material may, however, be permitted. Such finished material shall extend for a distance of at least 20 feet along the sides of the structure. All buildings on corner and double frontage lots shall have the required finished facade facing each street. No plain concrete block building or metal-faced building, except those with an attractive finished surface mentioned above, shall be permitted. Samples of all materials shall be furnished to the Plan Commission for review and approval.