Tested in the lab, HVAC system efficiencies are measured at their peak in almost perfect conditions. Repeating those results in the real world takes knowledge and effort both when the system is installed and as it is maintained. A significant part of real-world efficiency is the duct system. There are diverse types of ductwork for unending applications. Normally, that is the topic that HVAC contractors could argue about. This time, however, the conversation turns to duct sealing and what it means in terms of system efficiency and energy savings.