Question on NFPA 13, Ss 18.104.22.168.1 ~ 22.214.171.124.1.2, specifically concealed spaces not requiring sprinkler protection.
I have a request from a business that wants to put in cove lighting where the backside would be open to the environmental space above the drop ceiling. This environmental space would be/is unprotected. There is full coverage below the ceiling and the reason they want to leave the backside of the cove lighting, trench if you well, open, is to use the environmental space as a plenum, no ductwork to the ceiling. From reading 8.15.1, it seems vague on whether the plenum needs ductwork to the ceiling or leaving a portion(s) of the ceiling open to allow a return air unit to pull from the environmental space and thus pull from the occupied space.
I'm leaning toward requiring the cove lighting trench to be closed and the plenum attached to the ceiling as needed. Thoughts?