In one aspect there is provided an insulated modular roof system for a roof structure. The system comprises a plurality of modular panels suitable for installation onto the roof structure and a water-proof membrane. Each of the plurality of modular panels comprises a first planar member, an insulating layer covering substantially all of the first planar member and a second planar member suitable to cover substantially all of the insulating layer. Preferably, the system further comprises a joint closure member and a joint fill material suitable to fill any empty space between any abutting modular panels. The water-proof membrane may be provided in sections on each of the plurality of modular panels.

A composite panel, has: an insulating subpanel having a bottom face to be secured to a substrate and a top face opposed to the bottom face, the top face and the bottom face delimited by interconnected edges of the insulating subpanel; a polymer membrane adhered to a portion of the top face, the polymer membrane including a flap, the flap extending from a membrane edge of the membrane to a junction between the flap and a remainder of the polymer membrane, the junction being recessed inwardly from an edge of the interconnected edges of the insulating subpanel such that a portion of the top face of the insulating subpanel is free from attachment to the polymer membrane, a length of the flap extending from the membrane edge to the junction being greater than a distance between the edge of the interconnected edges and the junction.

A composite, insulated, structural panel, that includes an exterior face comprising a length and a width, an opposing interior face comprising the length and the width, a foam core disposed between the exterior face and the interior face, and a first plurality of reinforcement ribs attached to the interior face and extending laterally along the width, and extending outwardly into the foam core.

Coupling system (3, 30) for coupling building panels (1, 2; 31, 32) or sandwich panel comprising two cover sheets (5, 6; 33, 34, 36, 37) and a core (4, 39) of insulating material sandwiched between the two cover sheets, in particular for building a roof structure. The building panels have matching coupling edges (7, 8; 40, 41), profiled to define one or more water discharge channels (19; 59, 64) running substantially parallel to the coupling edges.