advanced building skins 14 | 15 June 2012 - lamp.tugraz.at - Graz ...
advanced building skins 14 | 15 June 2012 - lamp.tugraz.at - Graz ...
advanced building skins 14 | 15 June 2012 - lamp.tugraz.at - Graz ...
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Rdd [-]<br />
0.50<br />
0.45<br />
0.40<br />
0.35<br />
0.30<br />
0.25<br />
0.20<br />
0.<strong>15</strong><br />
0.10<br />
0.05<br />
6 mm Flo<strong>at</strong> fg023066<br />
R 0° p-pol. (=s-pol.) calc.<br />
R 20° p-pol. calc.<br />
R 30° p-pol. calc.<br />
R 45° p-pol. calc.<br />
R 60° p-pol. calc.<br />
R 75° p-pol. calc.<br />
R p-pol. mess: 20°, 30°, 45°, 60°, 75°<br />
0.00<br />
300 400 500 600 700 800<br />
Wellenlänge [nm]<br />
Advanced Building Skins<br />
Figure 3: Reflectance spectra of 6 mm flo<strong>at</strong> glass for p and s-polarized light and<br />
different angle of incidence [1]<br />
As both the reflectance and transmittance values depend significantly on the glazing configur<strong>at</strong>ion,<br />
including the number of panes, glass chemical composition, co<strong>at</strong>ings, and surface structures, different<br />
glazing specimens not only have different U values and g values for normal incidence, but also show<br />
differently varying behavior when the incident angle is changed. Figure 4 shows th<strong>at</strong> co<strong>at</strong>ed glass, in<br />
particular, shows large devi<strong>at</strong>ions from the g value determined <strong>at</strong> an incidence angle of 0°.<br />
Figure 4: Calcul<strong>at</strong>ed angular functions of total solar transmittance g for three DGU [2]<br />
Inadequ<strong>at</strong>e consider<strong>at</strong>ion of the incident angle dependence would not be of interest for calcul<strong>at</strong>ing the<br />
thermal impact on <strong>building</strong>s if the total irradi<strong>at</strong>ion <strong>at</strong> non-zero angles did not contribute significantly,<br />
since the solar gain is the product of the g value and the incident solar energy. However, as figure 5<br />
shows, the opposite is the case. The incidence angle of 0°, for which the solar he<strong>at</strong> gain coefficient is<br />
determined conventionally, contributes insignificantly to the annual total, whereas significant thermal<br />
impact results for solar irradi<strong>at</strong>ion <strong>at</strong> incidence angles devi<strong>at</strong>ing from 0°.<br />
Note: Vari<strong>at</strong>ions in orient<strong>at</strong>ion have a less significant effect on the angular distribution than vari<strong>at</strong>ions<br />
of the tilt angle for constant orient<strong>at</strong>ion.<br />
- 3 -<br />
Rdd [-]<br />
1.0<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
6 mm Flo<strong>at</strong><br />
fg023066<br />
R 0° s-pol. (= p-pol.) calc.<br />
R 20° s-pol. calc.<br />
R 30° s-pol. calc.<br />
R 45° s-pol. calc.<br />
R 60° s-pol. calc.<br />
R 75° s-pol. calc.<br />
R s-pol. mess: 20°, 30°, 45°, 60°, 75°<br />
0.0<br />
300 400 500 600 700 800<br />
Wellenlänge [nm]
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