A conditional use is a use that would not be permitted generally or without restrictions throughout the zoning district but which, if controlled as to number, area, location or relation to the neighborhood, would promote the public health, safety, welfare, morals, order, comfort, convenience, appearance, or prosperity. Such uses may be permitted in such zoning districts as conditional uses if specific provisions for such uses are made in this article. The Board of Supervisors reserves the right to grant conditional use permits. Conditions imposed in connection with residential conditional use permits wherein the applicant proposes affordable housing shall be consistent with the objective of providing affordable housing. When imposing conditions on residential projects, specifying materials and methods of construction or specific design features, the approving body shall consider the impact of the conditions upon the affordability of housing.