Haustechnische Gesellschaft für Sanitär-, Wärme- und Lufttechnische Anlagen Gesellschaft m.b.H. (HTG) is a subsidiary of Ortner Ges.mb.h. and is located in Vienna. It specialises in the construction of building systems in the fields of heating, air-conditioning ventilation and plumbing.

Their work profile includes buildings for private and public research facilities, schools, office facilities, and hotel buildings.