Frosted (diffusive) glass model and spectral optical data

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I am using OS 1.11.0 with radiance to evaluate energy performance of a frosted glass in a renovation project in which a low E glass will be mounted to the interior side of the frosted glass. Therefore, I used glazing window materials in OS and modeled three layers: clear glass turning solar diffuse tab on/air/low-E glass. However, the calculation failed. So, I changed the layers to clear glass turning solar diffuse tab off/air/low-E glass turning solar diffuse tab on, then the calculation worked. Is is impossible to model diffusive outer glass?

Further, it seems to be possible to input spectral optical data in Glazing window materials of OS. How can I do this?

thanks in advance.