Suspended Ceiling

Dear all, I have a suspended ceiling with a 60 cm air gap between the panels and the reinforced concrete slab where all the electro-mechanical lies, but it doesn't act as plenum zone since that all return, supply, and exhaust are ducted. Now this zone where all electro-mechanical lies is an unconditioned zone with assumed temperature of 80F. As for the basecase simulation, I've set the concrete floor assembly U-value as per ASHRAE 90.1, but what about the Basecase for the gypsum-board separating conditioned zones from this false ceiling zone? can I use gypsum U-value from the eQuest library?, or should I model it same as developed case (actual design) where a 5 cm layer of insulation is placed over these panels? and in that case I won't gain any credit from this insulation layer. Another question is that these zones are covered by veiling glass with insulation layer on all facades, so in basecase; should it have the same U-value as exterior wall since that it is opaque (veiled) glass area?