What does the term 'static pressure' refer to in HVAC ductwork?

The term 'static pressure' in HVAC ductwork specifically refers to the pressure exerted by the air in the duct system when the air is not moving. Static pressure is an important measure because it indicates the resistance to airflow within the system and helps to determine how effectively air is delivered to the conditioned spaces.

Understanding static pressure is crucial for system design and balancing. It provides insights into how much pressure is available to push air through ducts, which affects the overall efficiency of an HVAC system. High static pressure could indicate restrictions in the ductwork, such as blockages or poorly designed duct runs, which can impede airflow and lead to system inefficiencies.

The other options do not accurately capture the definition of static pressure as it specifically pertains to the condition of air within the ducts when there is no movement. For instance, static pressure is not related to the pressure of moving air, total pressure, or pressures influenced by external environmental factors, which are described by other terms such as dynamic pressure or atmospheric pressure.