Buildings are crucial to addressing energy problems because they are large consumers of end-use energy, and potential exists to dramatically improve their efficiencies. However, the pace of innovation in buildings is generally characterized as inadequate, despite the implementation of an array of policy instruments aimed at promoting efficiency. The literature on innovation in the building industry provides several explanations including: fragmented decision-making, principal agent problems, inadequate information, and limited learning across heterogeneous projects. We investigate the innovation process for buildings in the U.S. with a case study of patenting in energy management control systems (EMCS) for commercial buildings and programmable thermostats (PT) for residential buildings. Using U.S. patent data, we find that: (1) patenting activity peaked around 1980, subsequently declined, and then increased considerably in the past decade; (2) commercial, rather than residential, buildings account for the recent increase; and (3) building control technologies have benefitted from inventions originating outside the industry, notably from electronics and computers, with a shift toward the latter in recent years. (C) 2012 Elsevier Ltd. All rights reserved.