This is a project we are working on now (March 2014). The building was originally a school and is now being remodeled into a house. This living room is under a flat roof. Working with the owner we decided upon an energy efficient roof system: R20 open-cell spray foam under the roof deck; R10 ISO board on top of the roof deck, and finally a TPO membrane. Insulation on the roof deck minimized thermal breaks in the roof assembly while open-cell spray foam insulation, an air barrier, under the roof deck prevents the possibility of condensation.