This project had multiple layers of felt. This is a bad deal for a few reasons. The first is the heat load which was discussed in a previous photo. Second would be the inability to inspect the decking for rotten wood if all the felt is not removed . Anther major issue is is that most manufacturers warranties will be voided if there are multiple layers of felt.
Notice all the felt is being removed from the roof. One of the reasons we remove all the felt is to cut down on the heat load. Felt paper is an asphalt product so multiple layers of felt will cause a heavier heat load thus the attic will not cool off as fast when the sun goes down. It will also heat up faster when the sun comes up causing higher cooling bills.