Building simulation for energy efficient solar shading

The external horizontal shading device is an important climatic design element in the tropical climate. According to the revi ew, little is known about the in fluence of external horizontal shading device on reducing the solar heat gains, daylight penetration and the building energy consumption. Another important aspect is that the review on energy audits indicated a high intensity of energy consumption (an average of 269kWh/m2) for office buildings in Malaysia. However, significant energy savings can be achieved in buildings if they are properly design and operated. Therefore, it is important to investigat e the above interrelated issues to determine appropriate solar shading design strategies for the corresponden ce climate conditions. Also, early design decisions are the most effective than maki ng changes at later stag es after construction, which is time consuming and costly. According to the literature review, energy perfor mance of high-rise building is influenced by several design variables. The best option to optim ize the total building energy consumption is to test the number of design alte rnatives, which is time consumi ng and laborious approach. The other way of dealing with the problem is by varying one variable at a time and keeping the others fixed at reasonable practical values in order to de termine the effect of the particular variable on the energy performance of the building

Mitigating Thermal/Solar Heat Gains on Pavements and Its Influence on the Environment

With the vast quantity of natural vegetation being replaced by heat absorption materials due to urbanization, incident solar radiation is seen to be one of the most prominent heat sources. This increases the storage of sensible heat on these materials which accumulates heat impinged on the surrounding surfaces and is entrapped within the urban canyon. A large percent of the urban fabric is seen to be covered by pavements. It is therefore likely that the outdoor thermal environment is most influenced by the surface temperature of pavements increase the overall air temperature as well as the surface temperatures of the wall – hence temperature transfers to the interior, contributing to the operational indoor temperatures. This paper presents a review on paved surfaces aimed at studying the process of thermal heat gains of pavement materials with respect to their surface temperature under continual exposure to solar radiation. An experiment was carried out on three pavement materials to determine its surface temperature during the whole period of the day. Findings show excessive heat on paved surfaces especially during the day. Cool pavements (Porous/ high solar reflectance) however were significantly lower in surface temperature than the conventional impermeable pavements for all paved materials sampled because of its high reflectance and porous nature. This review analysis shows that an improvement on the thermal properties of outdoor spaces can be expected if the solar reflectance of paved surfaces is increased by retrofitting and the porosity be a key feature on the surface of pavements. Keywords: Pavements, Heat gain, Surface Temperature, Solar Radiation.

Empirical validation of daylight simulation tool with physical model measurement

Problem statement: In recent years, daylighting simulation tools have been increasingly used by many architects, engineers and researchers to evaluate the day lighting performances of building design. Most of these tools employ CIE sky models for simulation. However, the accuracy and applicability of these tools for tropical sky are doubtable. The aim of this study was to validate the computer simulated result with scaled physical model results measured under real tropical sky. Approach: Daylighting model was constructed using scaled physical model to be tested under real sky measurement. The same model was configured in Desktop Radiance 2.0 to perform day lighting simulation experiments. All the measurements were carried out under intermediate and overcast tropical sky conditions in Malaysia; while related CIE sky conditions were used for simulations. Results: Due to the CIE sky conditions are very dissimilar from the actual tropical sky; simulated absolute value results such as external illuminance, absolute work plane illuminance and surface luminance recorded high mean differences from the measured results, with 81.63; 71.06 and 49.71%, respectively. However, relative ratios such as Daylight Factor (DF) yielded mean difference of 26.06% and luminance ratio was 29.75% only. The average mean difference was 44.37%. Conclusion/Recommendations: To compare the performances, relative ratios such as DF and luminance ratio showed better accuracies. For future research, validation on other parameters can be performed such as orientations, angle of the overhang, glazing, window sizes, colors, environment settings and electric lighting

Water bodies an urban microclimate: a review

In urban areas, water bodies have a positive effect upon microclimate of the surroundings with the relative cooling impact it has on evaporative procedure. Hence, evaporative cooling might be one of the pretty efficient methods of passive cooling for urban spaces and buildings. Differences in temperature between the urban space and the non-urban space which surrounds, is dubbed UHI (Urban Heat Island) effect. Water bodies have also been proven to be influential methods of decreasing urban temperatures. A water body temperature is capable of being lower than the surrounding urban environment around 2 - 6 °C. According to these findings; one may conclude that the rise of evapotranspiration in cities, that has roots in vegetation and water body, can efficiently mitigate the influence of the urban heat island. Unfortunately, the effect that water bodies can have upon urban temperatures has not been thoroughly assessed in previous studies, specifically the difference between the daytime and night time influences of water bodies, and the matter the how urban design may be in influential in moving the cooling influence from the water bodies toward the city. This paper provides a theoretical background for the problem and reviews the related literature

Implementation of solar chimney in orang asli settlement in Bukit Lagong Selayang

In compliance with the Malaysia Housing Policy, providing adequate, affordable and quality housing for all is the major goal. The case study house for the study is in the existing settlement for Indigenous people located at Bukit Lagong, Selayang, Kuala Lumpur which was built under the 7th Malaysia Plan (1996-2000). However, the poor thermal performance of the existing house does not satisfy the occupants and cause most of the occupants rather carrying out the daily activities outside the house during the daytime. A field measurement was carried out from 12am of 4 March 2011 to 11pm of 5 March 2011 in order to obtain the real-time data and compared with the CFD simulated result. The experiments followed by introducing solar chimney at the simulation model and examine the result of the thermal performance. The findings show that the thermal performance of the mean air temperature and mean air velocity of the indigenous house has been improved after introducing solar chimney by 2.6% and 15% respectively at the hottest hour compared to the measurement results. This has shown that the solar chimney is useful and functions as the stack ventilation tool in the tropics

Field investigation of indoor thermal performance in Malaysia air-welled terraced house

This paper aims to determine the performance of the air well system in a hot and humid tropical climate with existing full-scale air well of single-storey terraced house. The application of air well in residential building widely applied in a traditional building, especially in the Middle East and Europe countries. However, resulted from the development, the application of passive cooling strategies such as air well is gradually replaced by a mechanical cooling system. The aim of the study is to investigate the cooling system role in tropics, where hot and humid climate the overheating of building interior are a critical dilemma due to solar penetration through building fenestration. A field measurement has been carried out in a single storey terraced house with built-in air well in Kuching, Sarawak for 5 days. The field measurement investigates the thermal performance of the single-storey terrace house air well under tropical context. The investigation was measured with U-12 HOBO data logger for temperature and humidity while the air velocity was measured with HD32.3 DeltaOhm measurement logger. Both types of the instrument placed in the air well in a vertical position while another U12 HOBO datalogger placed in a test room with window connected to air well. The outdoor weather data set were measured with HOBO U30. Findings show that the under Malaysia tropical climate, the mean air velocity induced by the air well throughout the measurement days marked as 0.91m/s while during the hottest hour of the measurement days, the air velocity induced in the upper air well could reach 1.09m/s with an outdoor air temperature of 33.6°C and solar radiation of 198 Wh/m². The findings of the study have explained the effectiveness of the air well in providing the thermal performance in the indoor environment and further study on modification of the air well configuration could enhance the airflow and air temperature

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

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 effectsin coastal cities, which need further researc

Thermal performance of single-story air-welled terraced house in malaysia: A field measurement approach

The provision requirement of 10% openings of the total floor area stated in the Uniform Building By-Law 1984 Malaysia is essential for natural lighting and ventilation purposes. However, focusing on natural ventilation, the effectiveness of thermal performance in landed residential buildings has never been empirically measured and proven, as most of the research emphasized simulation modeling lacking sufficient empirical validation. Therefore, this paper drawing on field measurement investigates natural ventilation performance in terraced housing with an air-well system. The key concern as to what extent the current air-well system serving as a ventilator is effective to provide better thermal performance is to be addressed. By adopting an existing single-story air-welled terrace house, indoor environmental conditions and thermal performance were monitored and measured using HOBO U12 air temperature and humidity, the HOBO U12 anemometer, and the Delta Ohm HD32.3 Wet Bulb Globe Temperature meter for a six-month duration. The results show that the air temperature of the air well ranged from 27.48?C to 30.92?C, with a mean relative humidity of 72.67% to 79.25%. The mean air temperature for a test room (single-sided ventilation room) ranged from 28.04?C to 30.92?C, with a relative humidity of 70.16% to 76.00%. These empirical findings are of importance, offering novel policy insights and suggestions. Since the minimum provision of 10% openings has been revealed to be less effective to provide desirable thermal performance and comfort, mandatory compliance with and the necessity of the bylaw requirement should be revisited

The impact of air well geometry in a Malaysian single storey terraced house

In Malaysia, terraced housing hardly provides thermal comfort to the occupants. More often than not, mechanical cooling, which is an energy consuming component, contributes to outdoor heat dissipation that leads to an urban heat island effect. Alternatively, encouraging natural ventilation can eliminate heat from the indoor environment. Unfortunately, with static outdoor air conditioning and lack of windows in terraced houses, the conventional ventilation technique does not work well, even for houses with an air well. Hence, this research investigated ways to maximize natural ventilation in terraced housing by exploring the air well configurations. By adopting an existing single storey terraced house with an air well, located in Kuching, Sarawak, the existing indoor environmental conditions and thermal performance were investigated and monitored using scientific equipment, namely HOBO U12 air temperature and air humidity, the HOBO U12 anemometer and the Delta Ohm HD32.3Wet Bulb Globe Temperature meter. For this parametric study, the DesignBuilder software was utilized. The field study illustrated that there is a need to improve indoor thermal comfort. Thus, the study further proposes improvement strategies to the existing case study house. The proposition was to turn the existing air well into a solar chimney taking into account advantages of constant and available solar radiation for stack ventilation. The results suggest that the enhanced air well was able to improve the indoor room air velocity and reduce air temperature. The enhanced air well with 3.5 m height, 1.0 m air gap width, 2.0 m length was able to induce higher air velocity. During the highest air temperature hour, the indoor air velocity in existing test room increased from 0.02 m/s in the existing condition to 0.29 m/s in the hottest day with 2.06 °C air temperature reduction. The findings revealed that the proposed air well could enhance the thermal and ventilation performance under the Malaysia tropical climate

Optimum overhang geometry for high rise office building energy saving in tropical climates

Intercepting the radiant heat wave using external solar shading before penetrating to the internal environment through the envelope openings is the main criterion to prevent solar heat gains into the building. In hot and humid climates, one draw back of using the external shading device is the risk of reducing daylight level in the interior space, which in turn increases the use of artificial lighting. Therefore, 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 device strategies as design solutions in hot and humid climates. This study investigates the effect of six different depths of external horizontal shading device on incident solar radiation, transmitted solar heat gains, natural-light penetration, building cooling and energy consumption. The experiment was carried out using a standard, single fenestration perimeter office room in a typical high-rise office building. The investigation is conducted using the eQUEST-3 dynamic energy simulation program supported by the DOE2.2 calculation engine. The results showed that overhang ratios of 1.2, 1.6, 0.6 and 0.8 reduced the incident direct solar radiation more than 80% on the east, west, north and south orientations respectively. The target illuminance of 500lux for internal lighting was obtained for overhang ratios of 1.0, 1.3, 0.2 and 1.0 on respective orientations. Further, findings indicated that deeper natural light penetration can be achieved through the bare window under Malaysian sky conditions compared to the common rule of thumb of 2.5 times the window height on all orientations considered. The findings also revealed that optimum energy savings of 14%, 11%, 6% and 8% were achieved by optimum overhang ratios of 1.3, 1.2 and 1.0 on the east, west and north, south orientations respectively. 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