Disclosed herein is a solar thermal collector system that is particularly configured for installation on a flat roof of a building. In accordance with aspects of a particular embodiment of the invention, the solar thermal collector system includes a solar thermal collector module having a glazing sheet at a top, exterior surface, and an absorber sheet within the module positioned below and spaced apart from the glazing sheet. At least the absorber sheet is fluidly connected to a fluid handling system, and carries a working fluid that is heated in the module by the sun and transfers such heat to equipment connected to the module by the fluid handling system. The module is preferably provided a thermally actuated valve that allows the working fluid to also flow through the glazing sheet, which results in self-regulation of the temperature of the module below a critical design temperature.