Insulating ceiling above a garage

I would like to insulate a bedroom floor above a garage and have been thing of using blown insulation between the floor beams. What would be the best type to use and I do not want it to interfere with the heating pipes and elctrical cable. Blown rock wall?, I assume polystyrene would be bad! Thanks

In an earlier contribution to this discussion,
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If it's not already insulated, it was presumably built a long time ago - and almost certainly doesn't comply with current building/fire regulations.
Why not do the job properly by taking down and then re-making the garage ceiling? While it's down, you can pack between the joists with rockwool (far better than loose fill), install a vapour barrier, and then fit however many layers of plasterboard are required for fire regs (probably 2 with non-overlapping joints?)