Abstract: A roof assembly for covering a building includes a first structural layer coupled to the framework of the building, a second structural layer positioned above the first structural layer, and an insulating layer including a roof insulation panel positioned between the first and second structural layers. A ventilating purlin extends between and contacts the first and second structural layers along at least one edge of the roof insulation panel. The ventilating purlin transfers loads from the second structural layer to the first structural layer without using the insulating layer for structural support. The ventilating purlin also includes at least one ventilation opening positioned to enable air flow through the ventilating purlin into a ventilating layer of air space formed between the insulating layer and the second structural layer. Thus, the ventilating purlin permits full ventilation of the roof assembly.