Insulation, Radiant and Vapor Barriers - Insulating Converted Garage

I have a room that was formed out of a converted garage. The room has a drop ceiling with a flat roof.

Is it OK to place insulation between the drop celing and the roof? Any reasons that I should not do this? Anything that I should be aware of? What product should I use and what is the best way of doing this?

Thanks.

Houses without insulation do not require ventilation, this is because heat is not being retained. When you insulate a home because the insulation retains heat to prohibit heat loss, the probability that condensation will occur in the attic or space between the heated space and unconditioned space is high.

In your situation if I was to advise you to insulate above the drop ceiling, condensation would more than likely occur in the space between the drop ceiling and flat roof. If you really want to insulate this area, you will need to find a way to ventilate it.