Can I Lay Insulation on the Backside of Tiles to Improve R-value and NRC?

In general, ceiling tiles are not designed to bear any weight other than their own, which is why grid-supported brackets are required when mounting things like recessed can lights and ceiling speakers. The same is true when it comes to additional insulation; the weight of the insulation on the back of the tile, whether the tile is made from vinyl or mineral fiber, will probably cause that tile to sag over time. There are three very good alternatives to improve ceiling R-value and NRC value, however:

1. Use rigid insulation that will rest on top of the "spines" of the T-bar grid system. This gives you increased insulation value, but without putting weight on the tiles themselves.
2. Insulate the hidden ceiling structure above your suspended ceiling. This insulation might take the form of insulation batts stapled between the rafters or floor joists from which your drop ceiling grid is hung, or of rigid insulation mounted directly to the ceiling structure above the T-bar.
3. Use AcoustoTherm Backpanels in conjunction with your Ceilume feature panels to increase both R-value and NRC without introducing fiberglass insulating materials into the environment.