The Effects Of Room Orientation On Indoor Air Movement In The Warm-Humid Tropics: Scope For Energy Savings Zebun Nasreen Ahmed Associate Professor, Dept of Architecture, BUET, Dhaka, Bangladesh. Abstract This paper examines the effects of prevailing wind on room orientation and placement of windows, in a warm- humid setting like Dhaka. In humid climates one heavily depends on air movement to provide thermal comfort. The paper is based on a wind tunnel experiment, conducted in UK by the author, on the model of an existing test house in Dhaka, to determine pressure coefficients, from which indoor air movement under different inlet-outlet combinations were calculated for the worst situation scenario, ie, 3 pm readings of air speed and humidity. Calculated indoor air movement values were then assessed to determine comfort potential, and whether other sources of air movement using active energy, are needed to provide thermal comfort air movement. The results are then analysed to provide guidelines for room orientation and for location of windows in buildings, which aim to reduce active energy expended for comfort of the occupants. Introduction It has often been argued that tropical countries like Bangladesh, which are warm and humid for long spells each year, should have settlements that allow for as much air movement as possible. Building design and orientation should be planned to catch the available breeze. However, wind directions in the region are not constant throughout the year, and often, available wind speeds are not sufficient to generate favourable indoor airflow. It is on the hottest, most humid days when conditions are still, that a building occupant most usually needs comfort in the form of air movement. Ironically though, it is on these very same days that calm conditions prevail and hence, available natural wind proves to be inadequate. This paper examines the ability of natural wind-speed and direction, in the course of an average year, to provide comfort conditions in building interiors for eight main orientations in a typical residential building in Dhaka. In the event that natural flow is adequate in providing air movement sufficient to ensure thermal comfort, the use of fans and other mechanical devices for cooling can be minimised, thereby affecting energy savings. Table 1 PREVAILING WINDSPEED AND DIRECTIONS IN DHAKA, BANGLADESH MONTH WINDSP PERCENTAGE OF PREVAILING DIRECTION m/sec S SW W NW N NE E SE Jan 1.4 - - - 83 17 - - - Feb 1.6 11 22 6 44 17 - - - March 2.6 35 41 6 - 12 - - 6 April 3.7 94 6 - - - - - May 4.4 84 - - - - - 5 11 June 3.8 42 - - - - - - 58 July 3.9 28 5 - - - - - 67 Aug 3.3 26 - - - - - - 74 Sept 3.4 28 - - - - - - 72 Oct 2.5 16 - - 16 31 16 5 16 Nov 1.4 - 10 - 37 42 - 11 - Dec 1.5 - - - 50 50 - - - Yearly 30 7 1 19 14 1 2 25 Summer / rainy season 44 6 1 2 5 2 1 38 Winter (Nov-Feb) 3 8 1 54 31 - 3 -