The numerical simulation, design, and construction of a double glazed integrated collector storage (ICS) with compound parabolic concentrators (CPC) reflectors are presented. The design of the double glazing is optimized by means of numerical simulations under Tunisian climatic conditions. The numerical program used for the simulation consists on the transient resolution of the balance energy equations of each component of the solar water heater. Different proposed models of a double glazing are studied and compared with a reference case of a single glass ICS model. The simulation results have shown that the use of double glazing with argon layer and low-e coated lower glass instead of one glass cover significantly improves the thermal behavior of the ICS heater and visibly reduces its thermal losses during night. Taking into account these numerical results, a double-glazing ICS prototype-collector is constructed. The details of the construction, geometry, optical properties, and dimensions of the prototype are presented.