What is the primary purpose of the HVAC system?

The primary purpose of the HVAC system is to provide indoor heating, cooling, and ventilation. This encompasses the main functions necessary for maintaining a comfortable and healthy indoor environment throughout different seasons. An HVAC system is designed to regulate indoor temperature, ensuring that spaces are adequately heated during colder months and cooled during warmer months. Additionally, it plays a critical role in providing adequate ventilation, which is essential for circulating air and maintaining air quality within buildings.

While other options like filtering outdoor air, controlling humidity levels, and ensuring energy efficiency are important aspects of HVAC systems, they are secondary to the core function of providing thermal comfort and ventilation. For instance, filtering outdoor air helps improve indoor air quality, and managing humidity can enhance comfort and protect building materials. Energy efficiency is increasingly emphasized in modern HVAC design but supports the overall purpose rather than being the primary objective. Thus, option A captures the fundamental role of HVAC systems in creating a livable environment.