What temperature gradient is typically used for duct design calculations?

In duct design calculations, a temperature gradient of 20 to 25°F is commonly employed. This range is based on practical considerations regarding indoor and outdoor temperature differences as well as system efficiency. It accounts for variations in heating and cooling loads that buildings typically experience throughout different seasons, ensuring that the designed system can adequately meet the thermal comfort needs of occupants.

This gradient allows for effective heat transfer between the air moving through the ducts and the surrounding environment, optimizing HVAC system performance. A temperature difference within this range strikes a balance between energy efficiency and comfort, making it a preferred standard for many HVAC professionals when designing duct systems.