Duct design is a critical part of passing warm or cool air throughout a building. There are primarily four major types of ductwork that distribute and intake air in a Heating Venting and Air Conditioning (HVAC) system.

1) The trunk and branch method

2) Thee radial method

3) Thee spider method, and the perimeter loop all perform this task in different ways and usually correspond to a particular building type.

All duct design revolves around the furnace unit. Air conditioning, while its unit is located outside of a building, also passes through this unit in order to incorporate the same ducts. A furnace is normally located in the basement of a home or building and its size depends on the building. Homes frequently have a furnace about the size of a refrigerator, but large buildings can have multiple furnaces that can take up entire room's worth of space. Regardless of size, all ductwork revolves around this spot in a building because it is the source of all air being ventilated.

The trunk and branch method of duct design is one of the most common. Normally, this type of duct installation consists of two large, main ducts that exit the furnace in opposite directions, running directly below the middle of a building, much like a tree trunk. Several branch-like smaller ducts shoot off from this main duct. These smaller branches lead to individual rooms and provide heating and air conditioning.