A roofing system of a structure, the roofing system includes a roof deck, a barrier layer fastened to the roof deck, and roofing material being disposed over the barrier layer and the roof deck, the roofing material preferably made of nonflammable roofing members being exposed to the outside ambient environment. The barrier layer includes a reflective layer on one side of the barrier layer and a synthetic roofing underlayment forming a liquid water barrier layer on the opposite side of the barrier layer. A thermal insulation layer and a nonflammable layer is disposed between the reflective layer and the liquid water barrier layer. The nonflammable layer and the thermal insulation layer may be embodied as a fiberglass insulation layer.