What does the duct sizing method known as Manual D determine?

Manual D is a standard method used in the HVAC industry for determining the appropriate duct sizes and layout to ensure efficient airflow throughout a building. This method takes into account factors such as the air volume required for the space, the layout of the ducting, friction loss, and pressure drop to ensure that the duct system operates at optimum efficiency.

By accurately sizing ducts, Manual D helps to maintain proper airflow rates, minimize energy losses, and enhance overall system performance. An appropriately sized duct system also contributes to improved comfort levels within the conditioned space by ensuring that air is distributed evenly and effectively.

Other options relate to different aspects of HVAC design or efficiency but do not directly pertain to the specific function of Manual D. For instance, while speed of air in the duct system can be a consequence of correctly applying Manual D, it is not the main goal of the method. Similarly, the cost efficiency of the HVAC system and the energy consumption of the air conditioning unit are broader concerns that can be influenced by duct design, but they are not the primary focus of the Manual D sizing process.