Dilshan Remaz Ossen

A Preliminary Study of Thermal Comfort in Malaysia′s Single Storey Terraced Houses

Abstract In a tropical climate, passive cooling is difficult to achieve with respect to mass housing design. A good house design keeps the indoor environment favorable and comfortable during most of the year without the use of any mechanical devices. Terraced houses are typical examples with low comfort problem that need particular consideration. Low air velocity and high air temperature are experienced during the daytime and the wind effect is not well captured, especially in the single sided ventilation. Use of natural ventilation has been increasingly examined as an energy–efficient means to provide thermal comfort as well as a healthy indoor environment. This paper discusses the validation of Computational Fluid Dynamic (CFD) results and the measurement of thermal comfort in Malaysia′s single storey terraced houses. The thermal environment and comfort conditions were investigated using field measurement and CFD technique. Validation of CFD FloVent was carried out through the comparison of field measurements. Comparison of the results between simulations and measurements illustrated a good agreement. The simulations were performed on a selected day in a one–year climate condition. The results indicated that the design of single storey terraced houses is not effective in providing natural ventilation for achieving thermal comfort. The microclimate condition surrounding the terraced house indicated very low wind speed. Therefore, modification of the natural ventilation mechanism using a solar chimney as induced ventilation needs to be manifested and evaluated.

Thermal comfort of various building layouts with a proposed discomfort index range for tropical climate

Recent years have seen issues related to thermal comfort gaining more momentum in tropical countries. The thermal adaptation and thermal comfort index play a significant role in evaluating the outdoor thermal comfort. In this study, the aim is to capture the thermal sensation of respondents at outdoor environment through questionnaire survey and to determine the discomfort index (DI) to measure the thermal discomfort level. The results indicated that most respondents had thermally accepted the existing environment conditions although they felt slightly warm and hot. A strong correlation between thermal sensation and measured DI was also identified. As a result, a new discomfort index range had been proposed in association with local climate and thermal sensation of occupants to evaluate thermal comfort. The results had proved that the respondents can adapt to a wider range of thermal conditions.Validation of the questionnaire data at Putrajaya was done to prove that the thermal sensation in both Putrajaya and UTM was almost similar since they are located in the same tropical climate region. Hence, a quantitative field study on building layouts was done to facilitate the outdoor human discomfort level based on newly proposed discomfort index range. The results showed that slightly shaded building layouts of type- A and B exhibited higher temperature and discomfort index. The resultant adaptive thermal comfort theory was incorporated into the field studies as well. Finally, the study also showed that the DI values were highly dependent on ambient temperature and relative humidity but had fewer effects for solar radiation intensity.

Optimum Overhang Geometry for Building Energy Saving in Tropical Climates

abstract In hot and humid climates, one draw back of using shading devices is the risk of reducing daylight level which in turn increases the use of artificial lighting. It is important to understand the magnitude of energy consumption for cooling and lighting when shading devices are adapted in order to propose optimum external horizontal shading strategies as design solutions. This study investigates the effect of six different alternatives of external horizontal shading devices on incident solar radiation, transmitted solar heat gains, natural-light penetration and energy consumption. The study was carried out using a standard, single fenestration perimeter office room in a typical high-rise office building. The investigation is conducted using eQUEST-3, which is a dynamic energy simulation program supported by DOE2.2 calculation engine. The results showed several optimum geometry of the external horizontal shading device depending on incident direct solar radiation, transmitted solar heat gains, natural-light penetration and energy consumption. This study concludes, considering the trade off between total heat gain and natural-light penetration to optimize the total energy consumption as the best option in designing external solar shading in hot and humid climates.

Internal Shading for Efficient Tropical Daylighting in Malaysian Contemporary High-Rise Open Plan Office

In tropical climate, there is actually abundant quantity of daylight but yet to be utilised. The excessively high and unpredictable external illuminance could cause non-uniform indoor illuminance distribution and visual discomfort. In order to improve daylighting quality in contemporary high-rise open plan offices, proper design of internal shading should be investigated. A base model was derived from previous case studies for simulation using Radiance. Various venetian blinds, vertical blinds and light shelves were configured for the experiment. Daylight factor (DF) was evaluated for quantitative performance; work plane illuminance (WPI) distribution and vertical plane luminance ratio were investigated for qualitative performance. The findings demonstrated that generally blinds were not a good potential for daylight utilisation but good in reducing luminance contrast. Light shelves improved performances in DF and WPI distribution but increased the luminance contrast. Hence, integrations of light shelves and partial venetian blind (45° closed) were proposed as the effective designs for all orientations. The highest improvements of 31.8% in WPI distribution and 66.7% in luminance ratio were achieved for south and east orientations, respectively. This paper demonstrates that with proper internal shading design, effective daylighting depth can be significantly improved from typically used 2.5 H rule of thumb to 3.6 H.

Street geometry factors influence urban microclimate in tropical coastal cities: A review

Abstract Urban climatologists have moved smoothly towards urban geometry meso-scales as obstruction between buildings, streets, and urban environment. Urban climatologists and designers have expressed that urban geometry parameters affect urban microclimate conditions. Improper functioning of the geometry factors, particularly air temperature and wind speed, can increase the harshness of climate change and Urban Heat Island (UHI) defects, which are more critical in coastal cities of tropical regions. In this regard, the current study aimed to identify the impact of each street geometry factor on urban microclimate through a critical literature review. The research determined a total of twenty seven (27) factors within three clusters; 1) geometry factors, 2) meteorological factors, and 3) streetscape factors. The content analysis calculated the Depth of Citation (DoC) which refers to the cumulative importance level of each factor. The content analysis resulted air temperature (Ta) (DoC = 18 out of 28) is the most important street geometry factor that should be extensively considered in urban microclimate studies in coastal cities. In contrast, the factors (such as air pollution and traffic load) have received a minimum Doc (1 out of 28). The research has also analyzed the importance level of clusters through an expert input study using Grounded Group Decision Making (GGDM) method. The results show that meteorological cluster (92 %), streetscape cluster (86 %), and geometry cluster (85 %) have to be respectively implemented in urban microclimate studies in coastal cities. The research states there are new approaches have not yet been touched by urban climatologist affecting urban microclimate; included; surface materials, sea-borne dust and sand, user’s satisfaction, user’s thermal adaptive behavior. These approaches can potentially exacerbate UHI effects in coastal cities, which need further research.

Field investigation of indoor thermal environments in traditional Chinese shophouses with courtyards in Malacca

This study investigates indoor thermal conditions in traditional Chinese shophouses (CSHs) in Malacca, Malaysia, using field measurements and focuses on the cooling effects of courtyards. The results indicate that the indoor air temperature in the living rooms of CSHs was approximately 5-6°C lower than the outdoor temperature during the day primarily due to structural cooling effects with night ventilation, whereas the indoor air temperature at night was similar to the outdoor temperature. If the thermal adaptations of the occupants were considered, then the thermal conditions in the living rooms were acceptable for most of the day. The results indicate that the front courtyards functioned as a cooling source for the surrounding spaces in the CSHs.

Thermal Impacts of Vertical Greenery Systems

Abstract - Using vertical greenery systems to reduce heat transmission is becoming more common in modern architecture. Vertical greenery systems are divided into two main categories; green facades and living walls. This study aims to examine the thermal performance of vertical greenery systems in hot and humid climates. An experimental procedure was used to measure indoor temperature and humidity. These parameters were also measured for the gap between the vertical greenery systems and wall surfaces. Three boxes were used as small-scale rooms. Two boxes were provided with either a living wall or a green facade and one box did not have any greenery (benchmark). Blue Trumpet Vine was used in the vertical greenery systems. The data were recorded over the course of three sunny days in April 2013. An analyses of the results showed that the living wall and green facade reduced indoor temperature up to 4.0 °C and 3.0 °C, respectively. The living wall and green facade also reduced cavity temperatures by 8.0 °C and 6.5 °C, respectively.

Developing a BIM-based process-driven decision-making framework for sustainable building envelope design in the tropics

There is a rising concern for sustainability in the built environment. Therefore, numerous sustainable building certification and rating systems are developed throughout the world. However, the current methods of measuring, predicting, and optimising the sustainable building design have relied on a number of disjointed analyses to meet the discrete requirements for various building systems. The recent development of Building Information Modelling (BIM) technology allows complicated building modelling to be digitally constructed with precise geometry and accurate information to support various building project stages. Thereby, this study aims to integrate decision-making (DM) for sustainable building envelope design with BIM functionalities by considering the tropical climatic contexts in Malaysia. Several regional sustainable building certification systems and related literature were reviewed to identify the importance of evaluation and DM criteria. The findings were then compared with various BIM tools in terms of their applications, functions and workflows, in order to formulate a process-driven BIM-based DM framework (DMF) for sustainable building design in Malaysia. The proposed DMF will address the difficulties of DM in the early design development process, and will also allow for specific trade-off analyses of sustainability and objective-based optimisation using BIM.

Importance of a View Window in Rating Green Office Buildings

The essence of a view window (VW) in an office building is not only to bring an optimal balance between daylight and electric light, but also for psychological and health purpose. VW does not only allow the admittance of light and views, but indirectly affects the productivity and psychological wellbeing of office occupants; it has a link to the sustainability in both conventional and green buildings. This paper defines the function of a view window as it relates to green office building. Through literature review and an experiment conducted in room 432-01 located at B11 Faculty of Built Environment, Universiti Teknologi Malaysia. The function of VW in a green office building is highlighted; and the findings show that a VW would enhance sustainability in an office setting and has a dimension greater than 750mm above a finish floor level and less or equal to 2300mm above a finish floor level and with a wall to window ratio (WWR) of 25% to 40%.

Effect of the position of the visible sky in determining the sky view factor on micrometeorological and human thermal comfort conditions in urban street canyons

Poor daytime and night-time micrometeorological conditions are issues that influence the quality of environmental conditions and can undermine a comfortable human lifestyle. The sky view factor (SVF) is one of the essential physical parameters used to assess the micrometeorological conditions and thermal comfort levels within city streets. The position of the visible sky relative to the path of the sun, in the cardinal and ordinal directions, has not been widely discerned as a parameter that could have an impact on the micrometeorological conditions of urban streets. To investigate this parameter, different urban streets that have a similar SVF value but diverse positions of visible sky were proposed in different street directions intersecting with the path of the sun, namely N–S, NE–SW and NW–SE. The effects of daytime and night-time micrometeorological variables and human thermal comfort variables on the street were investigated by applying ENVI-met V3.1 Beta software. The results show that the position of the visible sky has a greater influence on the street’s meteorological and human thermal comfort conditions than the SVF value. It has the ability to maximise or minimise the mean radiation temperature (Tmrt, °C) and the physiological equivalent temperature (PET, °C) at street level. However, the visible sky positioned to the zenith in a NE–SW or N–S street direction and to the SW of a NW–SE street direction achieves the best daytime micrometeorological and thermal comfort conditions. Alternatively, the visible sky positioned to the NE for a NW–SE street direction, to the NW and the zenith for a NE–SW street direction and to the zenith for a N–S street direction reduces the night-time air temperature (Ta, °C). Therefore, SVF and the position of the visible sky relative to the sun’s trajectory, in the cardinal and ordinal directions, must be considered during urban street planning to better understand the resultant micrometeorological and human thermal comfort conditions.