Residential housing means a specific work or improvement within the Commonwealth, whether multifamily residential housing or single-family residential housing undertaken primarily to provide dwelling accommodations, including the acquisition, construction, rehabilitation, preservation, or improvement of land, buildings, and improvements thereto, for residential housing and such other non-housing facilities as may be incidental, related or appurtenant thereto. For the purposes of this chapter, medical and related facilities for the residence and care of the aged shall be deemed to be dwelling accommodations.