TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The stud bolts are fixed to the pitch of the roof with inserts made of polymeric material and/or with the cross members made of or coated with thermal insulating material, so as to interrupt the thermal bridges which would otherwise discharge onto the pitch of the roof, the thermal energy involving the pairs of metal profiles (b3) supporting the photovoltaic panels. The base profiles (b2) comprise: at least one longitudinal and lower groove with mouth open downwards, for fixing the cross members below the base profiles (b2) and for fixing other components on the ends of the base profiles (b2); large base wings with concave upward profile, useful both as base supports and as gutters for the collection and discharge of slight infiltrations of water; two robust side wings with grooves for gaskets on which the photovoltaic panels rest; a longitudinal and median groove, open towards the top, positioned symmetrically between the robust side wings, where the inner surface of which is provided with longitudinal ribs for the tightening of self-tapping screws via which the median centering groove is fixed to the longitudinal and median groove and open towards the bottom of the metal covering profile which with its wings bears at the bottom, the gaskets for cooperation in a sealing manner with the photovoltaic panels, and the longitudinal and median groove is not perforated at the bottom by the self-tapping screws, thus acting as a gutter; grooves having the function of a gutter positioned between the robust side wings and the longitudinal and median groove; and reinforcement means if necessary. The spaces between the wings with gaskets of the lower base profile (b2) and the wings with the gaskets of the upper metal covering profile contain the sides of the photovoltaic panels with ample transverse play to allow the photovoltaic panels to expand extensively also in the transverse direction. Throughout the front horizontal side of each second photovoltaic panel and of those that will follow it starting from the eaves line of the roof, the lower wing and an intermediate and consecutive part of a Z-shaped profile, made of stainless steel or other material suited to the uses in question, are fixed with material having the function of sealing agent and/or adhesive. The upper wing is arranged above the lower photovoltaic panel, having the function of a tile. On the intermediate and consecutive part of the Z-shaped profile, fastened with its own or additional adhesive, is a gasket made of any elastomeric material which provides a perfect air and water seal between the Z-shaped profile and the lower photovoltaic panel. The strip of material from which the Z-shaped profile is obtained has a limited thickness e.g. 1 mm, so that the horizontal joining areas between the photovoltaic panels can be clamped sealingly between the gaskets of the pairs of metal profiles (b3) supporting the photovoltaic panels. At the upper end of each base profile (b2), a stainless steel longitudinal plate is fixed to its longitudinal and lower groove, with screws and with inner plates similar to those used for fixing the cross members to the same base profile (b2). The edge of the plate projecting from the base profile (b2) has at least one hole to be anchored in an adjustable manner to an anchoring bolt integral with a bracket secured to a metallic bridge structure which is fixed on the ridge of the roof. On the eaves end of the base profiles (b2), a stainless steel longitudinal plate is fixed to the longitudinal and lower groove using screws and inner plates similar to those used for installation of the cross members. The projecting end of the longitudinal plate bears integrally and with transverse arrangement an appendix having any form for resting the horizontal side both of the photovoltaic panels which are positioned first on the base profiles (b2) and of the thermal insulation panels which will be positioned on the pitch of the roof, where the plates are provided on the sides with reference notches if necessary, useful for facilitating correct installation of the plates. The thermal insulation panels next to the photovoltaic panels are associated at the top, as an integral or fill part, to truss or perforated beams, which transversally engage the aeration chamber without obstructing the circulation of the air. The beams are made of any mechanically resistant material and have dimensions e.g. to touch, with interposed inserts of elastomeric material, where the lower face of the photovoltaic panels to make the latter more resistant to the mechanical stress is caused e.g. by snow, ice or footfall of maintenance personnel. The metallic bridge structures fixed transversally on the roof ridge comprise: base profiles (b1) which rest on the pitches of the roof, which are fixed to the latter using screws and inserts and at a center line of ridge bear integral pairs of vertical plates or parallel plates (227) in which the ends of vertical partitions are inserted in the manner of a drawer, splitting into upper two chambers, where the chamber of the ridge into which the aeration chambers below the photovoltaic panels are flow, if necessary brackets are fixed by screws to an intermediate portion of the parallel plates, the brackets can project from each metallic bridge structure to support the steel cable of the life line to which the operators can anchor with the snap hooks of their safety harness, the ends of the base profiles (b1) are fitted with double T uprights to which the brackets with the adjustable anchoring bolts of the upper end of the base profiles (b2) supporting the photovoltaic panels are welded, the ends of air-liquid type heat exchangers can be fixed to the double T uprights, and the exchangers are parallel to the ridge and e.g. to be crossed by the hot air which comes out of the cooling or aeration chambers below the photovoltaic panels and which flows into the upper two chambers from which it will then exit through discharge chimneys provided with electric fans if necessary to extract air from the cooling or aeration chambers; and an upper wall fixed to the top of the double T uprights, which counters to the base profiles (b1), provided with a horizontal walkable intermediate section and having a U-shaped transverse profile, so that its raised edges can be surmounted by the corresponding end edges bent downwards of consecutive covers of the ridge on which the discharge chimneys are provided, where the upper wall is provided with an intermediate slot crossed sealingly by a bracket of the life line, the upper wall is provided at the ends and on the center line with holes crossed sealingly by screws integral with forks anchored to the upper part of the double T uprights and cross members which can be tightened to form a bridge between the consecutive covers of the ridge, to lock them securely in position, are fixed to the screws by respective nuts, at the ends of the upper wall of each metallic bridge structure, small pantiles are obtained integrally by cutting and bending operations or are welded, the pantiles surmount the upper ends of the pairs of metal profiles (b3) supporting the photovoltaic panels are closed by insulation and sealing inserts, and the pantiles are positioned above upper plates connecting the photovoltaic panels to the ridge or chimney cover and the area joining these components is closed sealingly by a course of putty or sealing agent which prevents infiltrations of water both downwards and upwards. The area between the base profiles (b1) and the upper wall of the metallic bridge structures is closed by transverse walls to improve the walkability of the metallic bridge structures and to prevent the air flows coming from each cooling or aeration chamber, which cross respective heat exchangers and which reach the upper two chambers, from interfering with one another.