Guest Editors' Introduction: Green Buildings

h THE GLOBAL DEMAND for energy has been increasing at a rapid pace over the last several decades. The buildings in which we live and work are responsible for a major share of our energy and resource usage. In the United States in 2008, 39% of national energy use, 68% of electricity consumption, and 12% of water consumption was attributed to buildings in a study by the EPA, making buildings the single largest energy sink ahead of transportation and industry. In recent years, the rising costs of using fossil fuels, and the growing awareness of their impact on the environment, have led to concerted efforts to make buildings ‘‘greener.’’ The emerging field of green buildings encompasses various aspects of the building life cycle, including construction, renovation, operation, maintenance and demolition. Naturally, this is a multidisciplinary topic involving diverse fields including civil engineering, chemical engineering, and material science, in addition to electrical engineering and computer science. However, this special issue is motivated by, and focused on, the growing use of technologies that are relevant to the D&T communityVembedded computing, cyberphysical systems, sensor networks, and design principles and methodologies inspired by electronic designVin this area. There is growing consensus that these technologies are key to solving the challenges involved in making buildings greener. From the perspective of the electronics and computing industry, green electronics and computing has two important facetsVreducing the energy consumption in electronic systems themselves, and using them to make physical systems, such as entire buildings, more energy efficient. In other words, we can view electronics and computing as part of the problem (energy consumer), but also as part of the solution (energy efficiency enabler). The articles in this special issue will primarily address the later facet. One of the primary steps in improving energy efficiency of buildings is characterization and measurement, i.e., identifying where the energy is being consumed and where energy can be saved. This is important both at the macroscale, for example, at level of entire enterprises or large campuses, and the microscale by considering individual subsystems within a building. The energy consumed within buildings can be broken down into multiple sourcesVheating and cooling (HVAC), lighting, water management, computing and electronic devices, and other components depending on the building type. A number of efforts have recently looked at breaking down energy use within buildings and university campuses and identifying areas of energy waste which can be improved upon. The natural next step after energy use characterization is to make the energy data within buildings actionableVi.e., attribute the energy consumption of buildings and its subsystems to the actual occupants and activities within the physical spaces. This accurate energy attribution and apportionment serves several purposes. First, it provides users with an accurate account of their personal resource consumption. Second, it provides methods to analyze and visualize the data and to form meaningful policies to reduce energy usage. The task of energy attribution and apportionment at a fine granularity is however challenging, and solutions