What does the term 'ventilation' refer to in building systems?

Ventilation refers to the exchange of indoor and outdoor air, which is essential for maintaining air quality and comfort within a building. This process helps to remove indoor air pollutants, control humidity, and provide fresh oxygen, contributing to a healthier living and working environment. Effective ventilation systems can help to prevent issues such as mold growth, condensation, and stale air, ensuring that occupants breathe cleaner air.

The other options focus on specific aspects of air management rather than the process of ventilation itself. Heating the air indoors pertains more to the heating systems in a building rather than the exchange of air. Cooling air outside relates to outdoor environmental conditions rather than the exchange happening in the interior space. Lastly, the design of air ducts is about the physical infrastructure used to move air, but does not define the overarching principle of ventilation. Thus, the correct understanding of ventilation encompasses the vital exchange of air that supports both comfort and health within a building.