Controlling Indoor Climate. Passive cooling of residential buildings in hot-humid climates in China

University dissertation from Department of Building Science, Lund Institute of Technology, P.O. Box 118, S-221 00 LUND, Sweden

Abstract: Overheating is a paramount problem in residential buildings in hot-humid climates in China during summer. This study aims to deal with the overheating problem and the problem of poor air quality in dwellings. The main objective is to improve indoor thermal conditions by passive cooling approaches, climatisation techniques in buildings without auxiliary cooling from air conditioning equipment. A field study is carried out in southern China to ascertain the current situation of indoor environment in residential buildings. By literature survey a thermal comfort index SET (Standard Effective Temperature) is selected as a suitable index to evaluate indoor thermal environment in a hot-humid climate. This thesis focuses on the study of cross-ventilation in apartments, which is one of the most effective ways of natural cooling in hot-humid climate, but is also one of the least understood parts in controlling indoor climate. The Computational Fluid Dynamics (CFD) technique is used, which is a new approach, since cross-ventilation studies have been conventionally made by wind tunnel tests. The validations of the CFD technique are examined by a comparison between wind tunnel tests and computer simulations. The factors influencing indoor air movement are investigated for a single room. Cross-ventilation in two apartments is studied, and the air change efficiency in a Chinese kitchen is calculated with CFD techniques. The thermal performance of ventilated roofs, a simple and widely used type of roofs in the region, is specially addressed by means of a full-scale measurement, wind tunnel tests and computer simulations. The full-scale measurement compares thermal performance of ventilated roofs with other types of roofs. The wind tunnel tests examine ventilation behavior of the roofs and computer simulations study the parameters influencing the thermal properties of ventilated roofs. An integrated study of passive cooling approaches and factors affecting indoor thermal comfort is carried out through a case study in a southern Chinese city, Guangzhou. This thesis demonstrates that passive cooling measures have a high potential in significantly improving indoor thermal conditions during summer. This study also gives discussions and conclusions on the evaluation of indoor thermal environment; effects influencing cross-ventilation in appartments; design guidelines for ventilated roofs and an integrated study of passive cooling.

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