How Occupants Actually Use HVAC Systems (and Why It Breaks Design) (en Inglés) - Charles Nehme

Most HVAC systems do not fail because of bad engineering. They fail because of how people actually use them.

Designers calculate loads, select equipment, define airflow patterns, and set control strategies based on assumptions that appear reasonable on paper: stable occupancy, predictable schedules, minimal intervention, and compliance with intended use. Yet the moment a building is occupied, a different reality takes over.

Doors are left open. Windows are opened in conditioned zones. Thermostats are adjusted repeatedly. Spaces are repurposed. Personal heaters appear under desks. Diffusers are blocked by furniture. Meeting rooms sit empty for hours or are overcrowded without notice. The building becomes a living system influenced less by design intent and more by human behavior, perception, habit, and discomfort tolerance.

This book is not about criticizing occupants. It is about recognizing a fundamental truth: people do not interact with HVAC systems the way engineers expect them to.

Once this mismatch is understood, many long-standing HVAC problems become easier to explain-complaints in "perfectly designed" spaces, unstable temperature control, energy waste in high-efficiency buildings, and persistent comfort dissatisfaction despite advanced automation.

The goal of this book is to bridge that gap. It explores how occupants truly behave, why they behave that way, and how those behaviors systematically undermine even well-designed HVAC systems. More importantly, it shows how engineers, consultants, and facility managers can rethink design assumptions to create systems that are more resilient to real-world use.

This is not a theoretical comfort manual. It is a reality-based examination of how HVAC systems live and behave once people take control-intentionally or unintentionally.