NOVELTY - The device has an insulating layer (4) formed on undulated plates (2). A support unit comprises a washer (8) and a clamping nut (9), and is fixed with a fixation unit. Photovoltaic panels (5) rest on the support unit and cover the insulating layer. The support unit includes framework elements that are fixed to the fixation unit. I/T-shaped sections (13) rest on the elements and support the panels. The framework elements are assembled on an end of a locking hook (3) that locks the plates on purlins (1). An air space is formed between the insulating layer and each photovoltaic panel.    USE - Device for covering an existing roof (claimed) in a building.    ADVANTAGE - The design of the device obtains a simple, robust and firm connection between the photovoltaic sections and the panels. The device can be installed without requiring disassembling the existing roof, without disturbing exploitation of the building and without requiring a person in charge for the building to give interior access in a simple and rapid manner. The end of the longitudinal portion of the framework forms omega, so that maintenance of the support unit and the photovoltaic panels with the frame is obtained in a simple and easy manner. The air space allows better air circulation under the photovoltaic panels, so that concentration or the accumulation of moisture within the insulating layer or between the insulating layer and the plates is avoided and sealing of the roof and the lifespan of the device is reinforced, thus fulfilling the photovoltaic panels environmental requirements of the building and improving energy characteristics of the building. The photovoltaic panels completely cover the insulating layer, thus protecting the insulating layer from solar radiation i.e. UV rays, and extending the lifespan and the quality of polystyrene of the insulating layer. The sections are made of aluminum so as to assure robustness while limiting the weight of the device. The insulating layer reinforces the insulation of the roof. The device is simple to manufacture and highly resistant in time.    DETAILED DESCRIPTION - The plates comprise asbestos and are fragile. INDEPENDENT CLAIMS are also included for the following:    (1) a roof comprising undulated plates    (2) a method for covering an existing roof formed of undulated plates or having in section non-planar patterns.    DESCRIPTION OF DRAWING(S) - The drawing shows a transverse sectional view of a roof equipped with a covering device.    Purlins (1)    Undulated plates (2)    Locking hook (3)    Insulating layer (4)    Photovoltaic panels (5)    Washer (8)    Clamping nut (9)    I/T-shaped sections (13)