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Applying natural ventilation for thermal comfort in residential buildings in Singapore.

Article Excerpt
Abstract: This paper explores the potential of using natural ventilation for indoor thermal comfort in residential buildings in Singapore based on climatic data analyses. A typical year of weather data was selected by statistical analyses of weather data over a five-year period in Singapore. The characteristics of weather data for a typical year were analyzed with regard to temperatures, wind speeds, and wind directions. Thermal comfort models for natural ventilation applicable for Singapore were used for the assessment of thermal conditions. It was found that by applying natural ventilation, a thermally comfortable indoor environment can potentially be provided for a large number of hours in the year with optimum of facade designs for residential buildings (negligible heat sources). The study also developed facade design guidelines based on the required indoor air velocities for thermal comfort.

Keywords: Climatic data, Design guidelines, Fascade design, Indoor air quality, Indoor environmental quality, Natural ventilation, Residential buildings, Thermal comfort, Modeling, Singapore, Wind

Introduction

There is a growing interest in the application of natural ventilation in buildings due to the energy, indoor air quality and environmental problems associated with mechanically ventilated buildings. Various mechanical systems including HVAC systems in residential and office buildings contribute substantially to the energy consumption.

As the benefits of natural ventilation, including reducing operation costs, improving indoor air quality and providing satisfactory thermal comfort in certain climates, are recognized, passive cooling of houses using natural ventilation has become an attractive alternative to alleviate the associated problems with air-conditioned buildings. The concept of natural ventilation is well accepted and welcomed by people and designers in the world.

Although 86% of people in Singapore live in Housing and Development Board (HDB) residential buildings, designed to be naturally ventilated, residents tend to keep increasing the usage of air-conditioning for indoor thermal environment. The statistic data of energy usage in Singapore show that domestic energy consumption rose up to 58% of total energy consumption in 1998 from 18% of total energy consumption in 1988 and energy consumption per person was doubled from 1991 to 2001. For tropical regions, where the air temperature and relative humidity are generally high, the effectiveness of natural ventilation is questionable. Therefore, the investigation of natural ventilation applicability in hot-humid climates is significant for providing guidance to optimize facade designs. The purpose of this study is to test the availability of natural ventilation for the hot-humid climate regions in Singapore based on local climatic environment analyses.

Selection of Typical Year Data

For thermal analyses of local climate data, thermal conditions of one typical year data set (8760 hours) of weather conditions are required. Several kinds of typical weather data are currently available and the criteria for constructing a typical year weather data vary from one database to another.

Canadian Weather files for Energy Calculations (CWEC), produced by Numerical Logics, contain hourly weather observations representing an artificial one-year period specially designed for building energy calculations. International Weather files for Energy Calculations (IWEC) are derived from up to 18 years of DATSAV3 hourly weather data originally archived at the U.S. National Climatic Data Center (NCDC). The weather data are supplemented by solar radiation estimated on an hourly basis from earth-sun geometry, hourly weather elements, and particularly the cloud amount information. Solar and Wind Energy Resource Assessment (SWERA) developed high quality information on solar and wind energy resources in 13 developing countries. Typical meteorological year 2 (TMY2) was derived from a 1961-1990 period of record. The TMY2s are data sets of hourly values of solar radiation and meteorological elements for a one-year period. California climate zones 2 (CTZ2) updated weather data for 16 California climate zones for use.

Typical meteorological year is based on an empirical approach that selects individual months from a long period (30 years or more). Data sets occurring with the maximum frequency may be chosen to be included in the typical year. Since there is only a limited amount of weather data available in Singapore, a different criteria for construction of typical year weather data is applied. In this study, year 2001 weather data has been tested as a typical year data because it is the latest weather data available and has minimum amount of missing data. This reduces the amount of reconstruction and manipulation...