Energy Conservation through Interior Shading of Windows: An Analysis, Test and Evaluation of Reflective Venetian Blinds

Windows admit radiant and conducted heat energy as well as light and, for this reason, effective means for control is mandatory. Venetian blinds, providing continuous solar control, are ideal for energy efficient windows. They may be closed in the summer to block out undesirable solar radiation and opened in the winter to admit the valuable energy of the sun while providing year-round glarefree illumination. Architects, engineers and manufacturers have been reluctant to promote the use of venetian blinds as energy saving products because o f remaining uncertainties in the technology. This cooperative program involving industry, government and a university research team has developed predictive equations and has confirmed their ability t o accurately predict shading coefficients through experiments in an environmental simulator with an artificial sun. Ten venetian blinds with a wide range of surface finishes, including gloss and satin finish paints, polished aluminum, chrome deposition and units with different colors on the upper and lower surfaces of the slats were included in the experimental work.

In addition, the effect of solar incidence and slat angle on blind reflectance and shading coefficient was determined. The impact of varying incidence and slat angle on building energy load is discussed.