Drop Ceiling Return Air Plenum

This is most common in commercial buildings schools hospitals or libraries.

Drop ceiling return air plenum.

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. Since air will always take the path of least resistance removing all or part of the dropped ceiling and reducing the plenum area can create unique pressure and return airflow patterns which can vary on a daily weekly and seasonal basis and are usually at their worst when the air handling system is economizer mode taking in larger. The way i interpret that is while the plenum edge can have exposed wood wood framing can t extend into the plenum such as a partition wall extending above the ceiling to the lid with the drywall stopping just above the ceiling. Hi all curious of any and all opinions about using drop ceiling as a return air plenum.

The space above a ceiling is often used as a return air plenum in many types of commercial buildings meaning exhaust air from the room below is moved from the space through the plenum and then to ductwork leading to the central hvac system. Concrete slab ceiling above drop ceiling which is around 20 of store floor space and contacts only one 4 block. The space above the ceiling is not used as a return air plenum. The return air drop assembly is designed for the return air drop assembly is designed for up flow applications with side mount assembly and includes an exterior easy to access filter rack for a 1 in.

The assembly is constructed of 26 gauge sheet metal and the knock down design makes it easy to handle and assemble in the field. Space between the structural ceiling and the dropped ceiling or under a raised floor is typically considered plenum. I know it can and has been done but curious whether certain situations would not allow. Long story short my company was asked to move several ducts in order to install a higher drop ceiling.