Here we describe the results of a numerical and experimental study investigating the effects of applying an aerogel interstitial glazing unit (IGU) to the collection face of a model solar thermal collector. Concentrating solar thermal collectors (CSTs) concentrate incident light to give energy to a working fluid. Before entering the collector, the light must pass through a transmissive cover that helps to protect and insulate the collector. The experimental system is comprised of a simulated solar collector, through which water is circulated in a well insulated, closed loop system. To assess cover performance , the steady state water reservoir temperature was measured with different collector windows (aerogel IGU, plexiglas, and no cover) and at varying incident energy levels. In parallel, numerical models were explored, but it was determined that, in order to achieve results independent of experimentation, more known variables were required, which could have only come from experimental results, in turn making the models moot. There was some disagreement in experimental results between an initial and subsequent set of trials but, current results suggest the change in cover (including having no cover), has a negligible effect on the steady state temperature of the water. Further experiments are being designed to separate the insulating and transmissive functions of the IGU in order to better understand each component.