plenum thickness

[mustgetlicense]

G'evening, I have a quick question on calculation of the plenum thickness. I hope my question is clear at this late hour.

At an A.I.A. exam prep. lecture they said to find the deepest duct & add it to the deepest joist on the floor plan (even if they aren't in the same locations) & don't forget the light fixture space & that will be your plenum space. IS THIS TRUE?

-OR-

If the floor plan has five different areas of differing ducts & differing joists, am i supposed to just look for the area with the largest height combination in any of the five areas? (also not forgetting the light fixture space)

[Sparky83]

G'evening, I have a quick question on calculation of the plenum thickness. I hope my question is clear at this late hour.

At an A.I.A. exam prep. lecture they said to find the deepest duct & add it to the deepest joist on the floor plan (even if they aren't in the same locations) & don't forget the light fixture space & that will be your plenum space. IS THIS TRUE? NO!

-OR-

If the floor plan has five different areas of differing ducts & differing joists, am i supposed to just look for the area with the largest height combination in any of the five areas? (also not forgetting the light fixture space) This is the correct approach.

[mustgetlicense]

Thank you sparky83