For cooling demand, Case 1, which only uses the area ratio to calculate diffuse solar radiation (without consideration of reflectance or absorptance
), has the highest error rate (up to 11%) because the ceiling's absorptance
is only 20%, and using the area ratio to weight causes the model to overestimate the amount of diffuse solar radiation distributed on the ceiling, especially in situations with large floor/ceiling areas.
056 Layer Solar Solar Absorptance, Reflectance, a r Summer condition -- -- (Southeast) Heat-reflecting 0.
540 Low-e double glazing (8 mm) Inner glass of -- 0 754 Low-e double glazing (8 mm) Layer Solar Solar Absorptance, Reflectance, a [rho] TP glass 0.
For the base case, the results showed that higher shade absorptance (and lower reflectance) results in lesser rejection of solar radiation incident on the shades, consequently increasing shade temperatures.
The benefits of the advanced shading system are more prominent when a material with higher absorptance is selected.
The effect of overhang length becomes less significant for low absorptance shade fabrics.
It may be inferred that for the base case, as shade absorptance decreases, annual cooling energy goes down, for instance, it decreases from 7224 kWh for fabric 1 (59% absorptance) to 3712 kWh for fabric 3 (7% absorptance).
This effect is clearly shown by the fact that overhang length does not greatly affect annual cooling energy use for a low absorptance shade material.
Although the effect of fabric absorptance is clear for a small overhang, in case of a 1m overhang the trend isn't necessarily the same.
Examples of Properties that can be used as Design Variables Shading/daylighting system Properties considered as design variables Exterior roller shade Transmittance Interior/intermediate roller Transmittance, absorptance shade Exterior venetian blinds Reflectance, tilt angle, geometry Interior/intermediate venetian Reflectance, absorptance, tilt angle, blinds geometry Light shelf Reflectance, geometry, inclination Exterior awning Transmittance, geometry, inclination Prismatic/translucent glazing Transmittance, absorptance, thermal resistance
Visible and solar absorptance, transmittance and reflectance are critical factors in the space performance and should be all considered as design variables in the integrated analysis.