Building science is a field of study concerned with the technical performance of buildings, building materials, and building systems that draws upon physics, chemistry, engineering, architecture, and the life sciences. Understanding the physical behavior of the building as a system and how this impacts energy efficiency, durability, comfort and indoor air quality is essential to innovating high-performance buildings. Modern building science employs models of the building as a system (systems theory), and applies empirical techniques to the effective solution of building design problems.