After earning her master and doctoral degrees from the Massachusetts Institute of Technology (MIT), Ghaddar first worked as assistant professor at Kuwait University before joining AUB in 1990. She served as the chairperson of the Mechanical Engineering Department at AUB for six years from 2001-2007.

She is a founding member and served as the coordinator for four years (2000-04) of the Energy Research Group which is a multi-disciplinary group conducting basic and applied energy research in Lebanon and the region. Her primary research focus is in the area of computational and experimental heat transfer, enhancement for efficient cooling, solar energy applications, energy conversion, modeling of moisture and heat transport processes for walking clothed humans, thermal comfort, and energy efficiency. Recent work in thermal comfort has addressed an integrated approach to experimentally testing and modeling of a clothed-human body heat and mass transport processes and their interaction with their indoor environment. Applications would also lead to optimizing control strategies of in air-conditioning and heating systems for energy efficiency.

Her research approach for developing of ventilation models of clothed human from first principles has been original. Ghaddar has recently been appointed as Associate Editor to the American Society of Mechanical Engineering (ASME) Journal of Applied Mechanics and is a member of the Editorial Board of the International Journal of Thermal Sciences. Ghaddar is also a Fellow of the American Society of Mechanical Engineering and a member of the editorial board of the International Journal of Green Energy. In 2003, she has received the Outstanding Reviewer Award for the ASME Journal of Heat Transfer.

Professor Ghaddar has published more than 50 archived journal articles and more than 50 refereed articles in conference proceedings. She has managed and participated in many projects related to development of renewable energy training programs, climate change, and energy efficiency. Her research and funding have come from many sources including UNDP, US Department of State, American Society of Air conditioning and Refrigeration Engineers, European Commission on Education and Culture, Swedish Research Council-MENA, and National Lebanese Council for Scientific Research.

She is currently the Qatar Chair Professor in Energy Studies. She was elected a Fellow of the IAS in 2007.