This Small Business Technology Transfer (STTR) Phase I project will establish proof of concept for a unique, software-based Building Airflow Analysis Tool for measuring and optimizing airflow rates in commercial buildings. Using the existing Building Automation System (BAS), room temperature responses to controlled perturbations of airflow rates are used with a physics-based room thermal model and system identification (SI) routine to determine air changes per hour for each room. The proposed research focuses on developing algorithms that will work in BAS architectures and establish proof-of-concept in several large scale building tests, not only to validate the SI procedure, but also to establish actual energy savings and value proposition. The concept behind our technology is a unique integration of two diverse areas, bringing the dynamic nature of SI from control theory to the typically static or quasi-static aspects of HVAC system diagnostics and measurements. This research enables development of a smart building controls approach that will make building HVAC energy use more efficient. The successful proof-of-concept and large-scale validation of the basic idea, that are the goals of this research, will position the technology for commercialization. The broader impact/commercial potential of this project addresses a widespread problem that wastes billions of dollars and creates millions of metric tons of green house gases every year: heating, ventilation and air conditioning (HVAC) systems that move and condition too much air. This occurs since many large office buildings were designed when energy was cheap and their designs use minimum airflow rates above necessary levels for maintaining occupant ventilation. The technology developed through this STTR project will enable a unique software tool that can minimize airflow levels, while still meeting the ventilation and thermal comfort objectives. The new technology enables a new high margin business model by virtue of its low cost and scalability, all made possible because it is software-based and implemented through the existing Building Automation System. Commercialization of this technology will further catalyze energy efficiency investments in commercial buildings, a market that demands short payback periods and low risk investments. With commercial buildings representing an enormous built infrastructure with very slow turnover, development of this technology will enable a significant opportunity to improve domestic sustainability since commercial buildings account for 18% of the annual GHG emissions and 36% of the national electric demand.