ESTIMATION OF THE PERFORMANCE OF SUNSHADES USING OUTDOOR MEASUREMENTS AND

Abstract

Solar shading devices can significantly reduce cooling loads, improve thermal comfort and reduce potential glare problems in commercial buildings. However, measured data or tools to facilitate a comparison among various shading devices have previously not been available to designers. The Solar Shading Project at Lund University was initiated in 1997 to increase the knowledge on shading devices. This paper describes results from an extensive measurement program and recent developments of the software tool ParaSol v 2.0. The total solar energy transmittance (g-value) of various shading devices has been estimated by means of measurements in a real climate using a double hot-box arrangement. Monitored results are shown for external products (awnings, Italian awnings, venetian blinds, horizontal slatted baffle, fabric screens, solar control films), interpane (between panes) and internal products (pleated curtains, roller blinds, venetian blinds, solar control films). The software tool ParaSol has been further developed to include all these types of products. In general, external shading devices are the best in reducing cooling loads, internal products are the worst, while interpane products fall between these two. Further, internal products must have a high reflectance in order to yield a low g-value. The monitored average g-value within each group (g-sunshade) was 0.3 for external products, 0.5 for interpane products and 0.6 for internal products. On average, external products are twice as good as internal products in reducing peak cooling loads. With the software tool ParaSol, it is possible to estimate the effective g-value of shading devices for various orientations in combination with an arbitrary glazing system. Further, effects on heating and cooling (both peak loads and annual energy demands) and operative temperatures of an office room can also be simulated