The primary purpose of Manual D is best described as what?

The primary purpose of Manual D is focused on properly designing an air distribution system specifically for residential use. This manual provides guidelines for designing duct systems that ensure efficient airflow and proper distribution of conditioned air throughout a home. It takes into account factors such as the size of the rooms, the layout of the house, and the heating and cooling load calculations to create an optimal system that maintains comfort while maximizing energy efficiency.

In contrast, while matching system size to existing ductwork might be a consideration in some instances, it is not the primary focus of Manual D. It’s also important to note that Manual D does not specifically cater to commercial applications or the design of controls and fans, which fall under the purview of other manuals like Manual J and Manual T respectively. Thus, the correct answer aligns with the intention and guidelines laid out in Manual D, reinforcing its role in residential HVAC design.