Table 1: Design Variables and their Ranges for Illustrative Example Design Parameter Range Lighting Power Density (LPD) 0.8 - 1.5 [W/f[t.sup.2]] Window Shading Coefficient
(SC) 0.2 - 0.7 Exterior Wall R-Value 7.8 - 27 [hr-f[t.sup.2]-[degrees]F/BTU] Window U-Value 0.26 - 1 [BTU/hr-f[t.sup.2]-[degrees]F] Wmdow-to-Wall Ratio (WWR) 0.1 - 0.5
The glass shading coefficient
indicates the amount of solar heat gain through the glass.
Death of the shading coefficient? New sophisticated fenestration systems require new methods to determine their thermal performances.
Window and Drape Properties Property Window Drapes Exterior appearance Clear Diffuse Color/type Clear White muslin Visible transmittance, % 81 38.8 Indoor visible reflectance, % 14 60.5 Outdoor visible reflectance, % 14 60.5 Solar transmittance, % 66 34.9 Solar reflectance, % 11 52.3 Winter nighttime U-factor, 2.75 (0.48) - W/[degrees]C x [m.sup.2] (Btu/[degrees]F x [ft.sup.2]) Summer daytime U-factor, 3.13 (0.55) - W/[degrees]C x [m.sup.2] (Btu/[degrees]F x [ft.sup.2]) Relative heat gain, 563 (178) - W/[m.sup.2] (Btu/h x [ft.sup.2]) Shading coefficient 0.854 - Table 2.
Percentage of glazed areas, their shading coefficients
and the U- Values of facades were calculated.
In terms of insulation, meeting fresh air requirements and glazing, these buildings are definitely not up to par in terms of U-values and shading coefficients
. A lot of buildings still don't have a management system for their HVAC system, and the ones that do aren't well-managed.
Since the original development of the RTSM, solar heat gain coefficients (SHGC) have replaced shading coefficients (SC) as the key figure of merit characterizing window performance.
In the original development of the RTSM, shading coefficients were utilized for fenestration heat gain and no procedure was recommended for windows with interior shading, e.g.
Effective U-values and Shading Coefficients
of Preheat/Supply Air Glazing Systems.
Coated glass allows company to produce high performance IG units of exceptional gold color uniformity to achieve shading coefficients
as low as .14, and U-values as low as .24.