The answer to 'what does HVAC system do' is that an HVAC (Heating, Ventilation, and Air Conditioning) system is responsible for regulating the temperature, humidity, and air quality within a building. It works by circulating air through a series of ducts and vents, using a combination of heating, cooling, and ventilation components to maintain a comfortable indoor environment.
HVAC systems typically include a furnace or boiler for heating, an air conditioner or heat pump for cooling, and fans or blowers to circulate the air. They also often incorporate air filters, humidifiers, and dehumidifiers to control the moisture levels in the air. The HVAC system works to keep the indoor temperature and humidity at a desired level, while also ensuring proper ventilation and air circulation throughout the home or building.