Natural ventilation design for houses in Thailand Chalermwat Tantasavasdi a , Jelena Srebric b , Qingyan Chen c,* a Architecture Program, Faculty of Engineering Building, Rangsit Campus, Thammasat University, Room 713, Pathumthani 12121, Thailand b Department of Architectural Engineering, The Pennsylvania State University, 222 Engineering Unit A, University Park, PA 16802, USA c Building Technology Program, Department of Architecture, Massachusetts Institute of Technology, Room 5-418, 77 Massachusetts Avenue, Cambridge, MA 02139, USA Received 13 September 2000; accepted 15 March 2001 Abstract This paper explores the potential of using natural ventilation as a passive cooling system for new house designs in Thailand. The characteristics of past and present Thai houses are analyzed in terms of climate, culture, and technology. Based on the thermal comfort requirements for the Thai people and the climate conditions in Bangkok, the study found that it is possible to use natural ventilation to create a thermally comfortable indoor environment in houses in a Bangkok suburb during 20% of the year. This study also develops comprehensive design guidelines for natural ventilation at both the site planning and individual house levels by using computational ¯uid dynamics. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Natural ventilation; Computational ¯uid dynamics; Air velocity; Thermal comfort; House; Thailand 1. Introduction Natural ventilation has served as an effective passive cooling design strategy to reduce energy used by air-con- ditioning systems. For tropical regions, where the air tem- perature and relative humidity are generally high, the effectiveness of natural ventilation is always questionable. The vernacular architecture of Thailand, such as the tradi- tional Thai house in Fig. 1a, was designed to take advantage of the prevailing winds. The traditional Thai house is normally built with three notable characteristics: an elevated ¯oor, a steeply pitched roof with long overhangs, and a large open terrace. The elevated ¯oor prevents sudden ¯ooding, protects occupants from dangerous animals, and allows more wind to ¯ow through the living space. The long overhangs provide shade protect the house from rain. There is a thermal strati®cation in the house; the air temperature in the lower part of the house is lower than that in the upper part. The occupant usually stays in the lower, more com- fortable part of the space. The large open terrace, which occupies approximately 40% of the total ¯oor area, serves as a space for outdoor activities, and was an important space for the typical extended families of the Thai people of the past. Lives in the past two decades have changed dramatically. People tend to be more accustomed to air-conditioned environments. Nearly all cars, urban of®ces, schools, and houses are air-conditioned if the owner can afford one. About 90% of urban indoor environments are air-condi- tioned. However, people are concerned with the rising costs of electricity and fuel, especially when they have to pay utility bills for their own residences. In suburban houses, air- conditioning is used during the hot hours of the days. During the cooler hours, most people are still willing to open their windows and let fresh air in. Therefore, almost all windows in suburban houses can be opened. Passive cooling design elements are mostly ignored in modern house designs Fig. 1b). Dense areas in large cities such as Bangkok create a hot microclimate and discourage the use of natural ventilation because the buildings block each other from the wind. Current designs used many ideas and building materials from Europe and America without careful consideration for the Thai climate. For example, most new houses have no overhangs, resulting in easy penetration of the sun into the living area. The building envelopes are made of materials with a high thermal mass, such as concrete and brick. These materials store a large amount of heat during the day, and transfer it into the living space at night. As a result, houses are too hot without the assistance of an air-conditioner. The problems with current designs have prompted designers to rethink their designs, especially because of an increasing awareness of sustainability. To conserve energy and reduce CO 2 emissions, it is important to design Energy and Buildings 33 2001) 815±824 * Corresponding author. Tel.: 1-617-253-7714; fax: 1-617-253-6152. E-mail address: qchen@mit.edu Q. Chen). 0378-7788/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII:S0378-778801)00073-1