Professor Harrington is a registered architect with expertise in building systems, architectural detailing, and vernacular architecture. In pursuing interests in architectural composition techniques, he began studies in the importance of architectural details in the perception of buildings (supported by a National Endowment for the Arts Fellowship). This research led to studies of the Early Wooden Structures of Yugoslavia (supported by a Fulbright-Hayes Senior Research Fellowship and Honorary Fellowship). The majority of this later research has occurred jointly with Associate Professor Judith Bing of Drexel University. The results of this research have been disseminated in numerous academic papers and exhibitions of photographs and drawings at international venues. Over a ten-year period he was heavily involved, with colleagues from Bosnia & Hercegovina, in the Mostar 2004 Workshop & Symposia that focused on rebuilding strategies for the post-war rebuilding in the city of Mostar. Current research involves preservation and urban studies in the Old City of Jerusalem that have allowed continued work with many of the same international colleagues involved in Mostar.

He has had extensive experience in the design and development of urban projects in Philadelphia and the northeast of the United States, working at Vincent G. Kling Architects and as a project architect and associate of Mitchell/Giurgola Architects on a number of nationally and internationally recognized buildings and winning design competitions.