Buildings account for about 40% of energy consumption in most developed countries, and HVAC systems are where the biggest, fastest wins live. But diagnosing why a system underperforms takes more than equipment knowledge, it takes a solid grasp of the underlying physics and the ability to connect between theory and what’s actually happening in the field. Drawing on over 40 years bridging theory and hands-on diagnostic practice, Dr. Mohamed Hamed shares practical strategies for cutting building energy waste: equipment selection, load calculations, commissioning, and retrofit decisions, principles that extend directly to many industrial systems.