Hi all,

I recently came across a Life Cycle Analysis of Suspended Ceilings vs. Open
Plenums, initiated by CISCA [Ceiling and Interior System Construction
Association ( www.cisca.org )] which concluded that suspended ceilings are
more energy efficient because they have:

a) higher reflectances,

b) better heat-removal from luminaires, and

c) use lower static pressure and fan power.

I can understand (a) and (c) but (b) leaves me suspicious that the
return-air plenum was not considered in this study. As I understand it,
return-air plenums can be defined as separate zones from the usable spaces
(in this case: an office or a food store) but the suspended ceilings are
adiabatic. So , other than the savings for lighting and fan, I really don't
understand how there could be significant savings for the HVAC system if the
overall height of the rooms (plenum & usable space) is identical, and
cooling load of plenums are considered.

Is there something I'm missing?

Paul Hay