we replacing our torched down rubber roof and my contractor said we need to install a 1 inch rigid insulation..is the insulation needed?
on the outside, under the rubber? That's crazy. Don't go for it.
You would be foolish not to add the rigid foam under the new rubber roof. It gives you a new surface for an expensive roof. Definitely follow the contractors advice on this one.
There are a couple of types of torchdown, refer to the manufacturers instructions for the product being used. Most rubber or vinyl (pvc) do not fuse to the roof surface and depend on soft non-abrasive surface for maximum life.