The cold deck air in a dual duct system is supplied at approximately __________ on a year-round basis.

In a dual duct heating and cooling system, the cold deck air is typically supplied at a temperature that ensures effective cooling throughout the year, even in warm climates. The choice of 12.5°C (55°F) as the supply temperature strikes a balance between energy efficiency and comfort. This temperature is low enough to provide adequate cooling without resulting in excessive energy expenditure.

Maintaining the cold air supply at this temperature helps to manage humidity levels effectively and ensures that the air delivered to the conditioned spaces is comfortable for occupants. Additionally, this temperature fits well within standard practices for thermal comfort, aligning with both residential and commercial HVAC design principles.

The other temperature options are either too low or too high for efficient operation in a dual duct system used for year-round applications. Lower temperatures would be less common and might lead to discomfort or increased energy costs, while higher temperatures would not adequately serve the cooling requirement during peak summer months, leading to inefficiencies in temperature control and potential issues with humidity.