In humid climates a cavity space used as a return air pathway will pull humid air into the cavity space possibly encouraging mold growth or the deterioration of building materials.
Ceiling space return air plenum.
Other common framing cavities used as return air pathways or plenums are air handler platforms open floor truss cavities and dropped ceilings.
Space between the structural ceiling and the dropped ceiling or under a raised floor is typically considered plenum.
This is most common in commercial buildings schools hospitals or libraries.
Ceiling plenum 0 03 in.
Dropped ceilings or suspended ceilings are often installed so that the space between them and the floor above or the roof deck can be used as a return air plenum.
Of thumb for sizing various return air transfer assem blies are shown in table 1.
A plenum space is a part of a building that can facilitate air circulation for heating and air conditioning systems by providing pathways for either heated conditioned or return airflows usually at greater than atmospheric pressure.
Normally the space above the ceiling and the deck above is used to return air from the conditioned spaces below the ceiling to the air handling equipment.
If this is an area used as a return it is normally referenced as a return plenum.
However some drop ceiling designs create a.
The word plenum in the nec is used to describe both an air space and also various types of wiring methods that are specifically designed and tested for installation within these areas.
Fire protection within a return plenum is very important to the integrity of the entire structure and.