I am looking for information on initial deflection of composite precast-prestressed insulated concrete wall panels (in-place deflection due to self-weight.)  Much of the research I have done shows an assumed value of 0.5" with no differentiation for various panel heights and no reference to how this value was derived.

Intuitively one would think that the initial deflection of a 20' tall wall panel would be less than that of a 40' tall wall panel.  Or is the thinking that the prestressing strands would be designed to possess the strenght to prevent more than 0.5" of initial deflection?

Having trouble understanding why a precast wall panel would have initial deflection due to self weight.  Wouldn't these panels be cast flat on a rigid surface?  Why would they deflect?  Maybe it's just an allowance for the casting surface not being flat.

I am referring to when they are set in place (vertical) there is some out-of-plane deflection.

I wouldn't call that deflection unless it is due to eccentric prestressing.  No building materials are absolutely straight.  The 1/2" just sound like a tolerance, but like you, I would have expected the tolerance to be expressed as a function of the height.