To reduce solar gains, regions of the sky dome are masked, where the solar path will pass in the moments in which the shade will be desirable.But these regions masked by the shadow devices could also provide diffuse lighting, reducing the need for daytime artificial lighting.When a shadow device is perfectly designed it does not mask more sky than necessary avoiding unwanted solar incursion.During the early stages of architectural design many decisions that will affect the project's energy efficiency have not yet been made and information is lacking to carry out realistic energy or daylighting simulations.The objective was to define an index to qualify, from minimum input data, the effectiveness of a shaded opening by maximizing the visibility to the sky while minimizing undesirable unshaded solar paths.Using basic 3D models and AutoLISP algorithms, it was possible to calculate the aforementioned index.The results demonstrate that similar shadow devices present variable Solar Coupling Indices, explaining why the pre-design of an efficient shadow device is an unintuitive task.The method allows quantifying the gap between the best solar performance achievable and the performance achieved by a specific solar control device, helping to increase the energy efficiency of the architectural enclosures from the early design stages.