To insulate new metal roofing, it is easy to insulate it using rigid foam insulation. Place paper over the roof sheathing, staple this down, and install the rigid foam insulation on top of this layer. Place the pieces of rigid foam against each other, but do not permit them to overlap each other. Use duct tape to seal the seams between the sheets of foam. The roof will then be insulated and ready for the installation of the metal roofing. Rigid foam insulation may also be used in combination with fiberglass insulation to insulate an existing metal roof from underneath. If it can be accessed from underneath, then it will require spray foam insulation instead.