International Journal of Scientific & Engineering Research, Volume 8, Issue 4, April-2017 1039 ISSN 2229-5518 IJSER © 2017 http://www.ijser.org Effect of external shading device materials on air temperature of perimeter zones of commercial buildings with glazed facades Fariha Seraj Abstract— Commercial buildings of Dhaka city are characterized by excessive use of glazing. The glass surfaces create indoor thermal discomfort by increasing solar gain and the consequence is extensive use of air conditioning systems. It requires high energy demand and use of natural resources to satisfy comfort requirements. Shading device as a major element of building fenestration plays a significant role to reduce the solar heat gain. Among the variables of shading design, e.g. height, width, depth, material, material is less considered or considered for aesthetic rather than a key variable to control indoor air temperature. To reduce the cooling and lighting energy demand, effective shading design is necessary. The purpose of this study is to evaluate the performance of external shading device types and materials on controlling indoor air temperature. The three dimensional model of the two case spaces were created in Autodesk Ecotect Analysis 2011 to perform simulation. Indoor air temperature and the surface temperature of the shading devices for south and west oriented facades were observed for different shading typology and materials by simulation. Results show the relationship between orientation, typology and material. Most efficient shading devices are- horizontal louvers on horizontal plane and egg crate for south and west façade respectively. It was also found that the material with high thermal mass performs better than the low thermal mass materials. Index Terms— Air temperature, Commercial building, External shading devices, Perimeter Zone, Shading materials. ——————————  —————————— 1 INTRODUCTION kin and skeleton technology allows building with large glazing area which offers transparency, daylight in the visual environment as well as increase the amount of solar heat gain. These vertical surfaces of glass also act as heat trap. The thermal effect of these glass facades depends on the shad- ing provided and spectral properties of glass [1]. Use of shad- ing devices can ensure thermal comfort and reduce the cooling load by decreasing the amount of solar heat gain. Thermal benefits of shading devices are observed in many researches and its use is highly recommended [2], [3]. Baklah, Ismail and Rahman [4] found that indoor air temperature remain lower than the outdoor from 9am to 9pm by using a shading device while the time duration is 9am to 6pm in case of no shading device. This may be happen because of the direct exposure to solar radiation and the influence of heat transfer through ex- ternal building envelop and the effect of delay time. Spaces near the glazing area or the perimeter zones are critical area in case of ensuring thermal comfort for the occupants. It receives both the direct solar radiation from the sun and the inward heat flow from the absorbed solar radiation of the fe- nestration elements. Perimeter zones experience the largest fluctuations in temperature and human comfort. In case of both summer and winter, higher temperature difference be- tween indoor air and glass surface create discomfort due to radiant temperature asymmetry and increased (summer) and decreased (winter) operative temperature [5]. Effective use of external shading devices can improve thermal comfort con- ditions in perimeter zones. Most common studies on shading devices are limited to the orientation, configuration or geometry. Experiment related to thermal properties and surface properties of the exterior shad- ing device is rare. The objectives of this study is to investigate the thermal performance of different fixed external shading devices with commonly used materials in Dhaka during the last ten years and find the relation between orientation, typol- ogy and material. 2 CLIMATE OF DHAKA Based on Koenigsberger’s climate classification of tropical cli- mate, Bangladesh has a warm humid climate. Dhaka, the capi- tal of Bangladesh lies between 23°40‘N and 23°55‘N north lati- tudes and 90°20‘E 90°30‘E east longitudes. There are three dis- tinct seasons in Bangladesh: a hot, humid summer (March to June); a humid warm rainy monsoon season (June to October); and a cool, dry winter (October to March). In Dhaka, maxi- mum summer temperatures are observed during the hot- hu- mid season and it ranges from 30°c to 40°c. April is observed as the hottest month of hot- humid season [6]. 3 PERIMETER ZONE Perimeter zone is the spaces near the facades of a building. Depth of the perimeter zone is defined as 2700 mm from the maximum width of a workstation including secondary circula- tion space and an office cubicle. S ———————————————— • Author Fariha Seraj is currently pursuing masters degree program in Ar- chitecture in Bangladesh University of Engineering & Technology, Ban- gladesh, PH-01717559593. She is also a lecturer in Architecture Depart- ment at Dhaka University of Engineering & Technology, Gazipur, Bangla- desh. E-mail: fariha.seraj@gmail.com IJSER