To evaluate the visual comfort in
To evaluate the visual comfort in this GPCR Compound Library case, the Daylight Glare Probability (DGP) (Wienold and Christoffersen, 2006) was used as an indicator, which can be expressed as follows:where E is the total vertical eye illuminance [lx], is the solid angle of the glare source [sr], L is the glare source luminance [cd/m2], and P is the position index, i.e., a weighting factor based on position in the viewing hemisphere.
During the measurement, the following instruments were used:
Measurement protocol Horizontal illuminance data were collected on 55 points at a height of 0.95m (countertop level), as displayed in Figure 3. Vertical illuminance and luminance perceived by the observer were measured by taking 20 photographs (ISO 400, f/5.6, shutter time varied from 4s to 1/8000s) each at positions 1 and 2, at a height of 1.20m, with the view direction specified by the arrows in Figure 3. To determine the glare index value at both observer׳s positions, the obtained photographs were exported to Radiance, combined into High Dynamic Range (HDR) images using the Hdrgen programme, and then were analysed using Evalglare (Wienold and Christoffersen, 2006).
Simulation protocol Since the test room was not connected to the building׳s façade, the condition under a real window could not be observed. Therefore, the real window scene was modelled and simulated in Radiance. In addition, the actual conditions under all scenes of the prototype were also modelled and simulated, to give an insight in the difference between simulation and actual measurement. Comparisons were made between the values of horizontal illuminance at the central line, where points P1 and 1 were located (i.e., the blue-coloured points on Figure 3). The difference between the average illuminance, uniformity, and space availability was also evaluated. The front, top, and perspective views of the modelled prototype are displayed in Figure 4. The 12 TL5 lamps were modelled as 12 rows of cylinders, with a length of 1.20m and a diameter of 0.016m, constructed with a ‘light’ material. Assuming a total luminous flux of 4250lm for each lamp (Philips, 2013a), a conversion factor of 179lm/W between photometric and radiometric units (Ward and Shakespeare, 1998), and a solid angle of the incoming radiation of sr (Ward and Shakespeare, 1998), the following equation was applied to obtain the total radiance value of each lamp, i.e., 394W/(srm2) at the maximum setting.where L [W/(srm2)] is the radiance from the surface on which the material type is applied, Φ [W] is the total radiative flux of the light source and A [m2] is the projected light source surface over a solid angle Ω [sr] of the incoming radiance. In principle, Radiance solves the radiance equation for the red, green, and blue (RGB) values separately to obtain the radiance or the irradiance I [W/m2], if integrated over the solid angle. When a picture is rendered, the spectral irradiance values in red, green, and blue (I, I, I, respectively) are summed and weighted to obtain the single value of I, according to Ward and Shakespeare (1998): Eq. (6) was applied to obtain the red, green, and blue radiance components for the ‘light’ material. For the red-coloured lamps, the green and blue radiance components were assumed to be zero; for the green-coloured lamps, the red and blue were assumed to be zero; and for the blue-coloured lamps, the red and green were assumed to be zero. Hence, at the maximum setting, the red-coloured lamps were set to have a red component of 1487W/(srm2), the green-coloured lamps have a green component of 588W/(srm2), and the blue-coloured lamps have a blue component of 6059W/(srm2). For other settings, the values were adjusted proportionally. The PAR lamp was modelled as a thin cylinder with a diameter of 0.12m, aimed at an angle of 45°, and constructed with a ‘light’ material. Assuming a total luminous flux of 1415lm (Philips, 2013b), and by applying Eq. 3.5, a total radiance value of 223W/(srm2) is obtained. The red, green, and blue components were assumed to be equal.