The biggest HVAC company in the world is Johnson Controls. Johnson Controls is a global leader in the design, manufacture, installation, and service of heating, ventilation, air conditioning, and refrigeration systems. They have over 100,000 employees in more than 1,300 locations around the world and serve customers in more than 150 countries. Johnson Controls is also a leader in energy efficiency and sustainability, offering a wide range of products and services to help customers reduce their energy costs and carbon footprint.