This is a ceiling cartridge air conditioner from Fujitsu. There is no ductwork involved with these units, and they are perfect for conditioning smaller spaces, or in situations where ducts cannot be installed.
This is a modern, 96% effecient furnace. It is vented with PVC pipe, because it burns so effecienty that most of its waste is water. The joints on the ductwork have also been sealed with mastic, preventing air leaks and maintaining pressure inside the duct system.
This is an old 80% effecient furnace. While that may have been the standard for energy use 25 years ago, new furnaces we install have an effeciency rating of 96%.