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A simplified approach to calculate the daylight glare comfort class (imperceptible, perceptible, disturbing, or intolerable glare) on annual basis and for a grid of points in a space is presented. This method relies on the calculation of the vertical illuminance (Ev) for each grid point only, which is compared to an Ev threshold value for each daylight glare comfort class. These Ev threshold values are determined through a comparison with the Daylight Glare Probability (DGP) values on an annual basis through a fault-detection technique, for a reduced number of points. Compared to an annual calculation of exact DGP values on a certain grid, this approach is able to evaluate the daylight glare comfort classes only, but it is less time consuming. The paper presents and critically discusses this simplified method by means of its application to different case-studies: south and west oriented office in Turin (Lat 45.1° N), in which the DGP is assessed for three points in the space, considering glazing with different transmission properties (specular or scattering) and visible transmittances, as well as three operable internal shading systems (one venetian blinds and two roller blinds, for solar or glare control). For the presented case studies, the average error in the classification of the space according to daylight glare comfort classes is below 5% when comparing this simplified approach to related DGP values.

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The performance of a Double Glazing Unit (DGU) with a Phase Change Material (PCM) layer embedded in the cavity was analyzed in terms of the visual comfort perceived by the occupants. The analysis was carried out through a set of simulations, performed by the Radiance engine managed through Honeybee. As an input for the simulations, the visible transmittance Tv of PCM in solid (diffusing) state was used, based on previous laboratory measurements. The simulations were run for several specific times of the year: The two solstices and the autumn equinox, for different hours during the day. Other variables investigated were the site (Östersund, 63.2° N; Turin, 45.2° N; Abu Dhabi, 24.4° N), the room orientation (south; west), and the sky conditions (clear sky with sun; overcast). For comparative purpose, the simulations were repeated for the same boundary conditions in a room equipped with a selective glazing, with a Tv of 0.5. For each case, the visual comfort perceived by the occupants has been analyzed in terms of Daylight Glare Probability (DGP) in two different points in the room and of “Spatial Useful Illuminance” (percent of work plane points where the illuminance lies in the range 100–3000 lx). The results showed that the glazed package with PCM in most cases admits more daylight into the room, resulting into an increased glare (DGP values), but also in lower Spatial Useful Illuminance values.