Effectiveness of 'Penaga Lilin' (Mesua Ferrea L.) and 'Payung Indonesia' (Hura Crepitans L.) Trees as Thermal Radiation Filters in Outdoor Environment

In tropical climates, outdoor open spaces are highly exposed to solar radiation, resulting in uncomfortable conditions for pedestrians and other users. This influences the outdoor energy budget, leading to consequential thermal effects on the overall urban environment and contributing to the urban heat island effect. However, trees and other vegetation can play a significant role in reducing the effects of thermal heat in open spaces by filtering the incoming solar radiation before it reaches the ground. This study compares the effectiveness of two types of tree structural forms in filtering the thermal radiation. The trees are Mesua ferrea L. and Hura crepitans L., representing roundhead trees and horizontal shape species respectively. This study focuses on three variables that influence on solar radiation filtration, namely, transmissivity, leaf area index and shade form. Two evaluation methods were employed in this study; (i) a field measurement programme using a modified net radiometer and other related instruments, and (ii) Ecotect - a computer-based sunshading analysis.Results from this study indicated that both Mesua ferrea L. and Hura crepitans L. contribute significantly to direct thermal radiation modification below their canopies. The average heat filtration under tree canopy for Mesua ferrea L. was found to be 93% with 5% canopy transmissivity, 6.1 of leaf area index, and 35% of shade area. Meanwhile for Hura crepitans L. the average heat filtration under canopy was 79% with canopy transmissivity of 22%, leaf area index of 1.5 and 52% of shade area. Therefore, the study found that Mesua ferrea L. was better in filtering thermal radiation than Hura crepitans L. (93% and 79% respectively). This was attributed to the denser foliage cover and branching habit of Mesua ferrea L. with Leaf Area Index of 6.1 and allowing only 5% transmissivity as compared to Hura crepitans L. foliage density and branching system with Leaf Area Index of 1.5 and allowing for 22% transmissivity. Finally, the study also found that tree canopy characteristics of both species significantly influence thermal radiation filtration

Potential of individual and cluster tree cooling effect performances through tree canopy density model evaluation in improving urban microclimate

Technically, trees can provide cooling effect and able to reduce ambient temperature in its own way. This paper investigates the potential of individual and cluster tree cooling effect performances in improving urban microclimate through the evaluation of urban trees canopy density. The evaluation is based on the actual measurement of Leaf Area Index (LAI) and Leaf Area Density (LAD) and uses tested computer simulation tools ENVI-met. The study found that each tree has different capabilities in modifying each microclimate variables. However, it was revealed that the optimum effect of cooling of each tree was found during the hottest day to takes place approximately at 15:00 hours when the sun is overhead and solar angle height is close to 90°. Besides, trees with higher densities such as Ficus benjamina (i.e. LAI 9.7, LAD > 1.5) showed a remarkable reduction in comparison to the other loose density trees. It is also revealed that the implementation of cluster tree planting at larger scale could maximize the effects of cooling. Nevertheless, the downside of implementing high tree density could create a reduction of 63% of wind speed that might possibly influence the air movement in urban areas due to the drag force of tree canopy. The study concluded that the performance of tree cooling effect is well correlated with tree canopy density and it is also suggested the optimum cooling effect could achieved by higher tree density (mean LAD > 1.5) and larger tree quantities with tree cluster planting

Performance of groundcover on surface temperature reduction in the application of the extensive green roof

Malaysia’s climate is struggling with unusually hot and dry weather from February to May 2016. Temperatures soared to the limits of a new record. One of the solutions is by having green roof to reduce the heat transfer in urban microclimate and buildings. Thus, the evaluation of potential plants in this study is to understand their performance in surface temperature reduction. In this study, the field measurements was carried out with ten types of groundcover and one exposed soil and one selected concrete flooring on three clear days. The measurement is taken from 8 AM to 6 PM and recorded at one-hour interval using an infrared thermometer. This study was done to compare the surface temperature of green roof and exposed bare roof within the same outdoor ambient environment. The result from this study indicates that Eremochloa ophiuroides and Rhoeo spathacea are suitable for planting in extensive rooftop system. Eremochloa ophiuroides and Rhoeo spathacea significantly provide the value of the average percentage of surface temperature reduction which was 18.9% and 18.8% respectively. Thus, it is recommended that both species are suitable for extensive roof planting. This knowledge can be applied by professionals in landscape architecture, horticulture, urban planning and design to provide better rooftop planting material in tropical urban environments

A review of researches about human thermal comfort in semi-outdoor spaces

The role of human thermal comfort on sustainable architecture and urban design is substantial. To concentrate on outdoor thermal comfort subject as well as indoor thermal comfort is a key to solve the global warming andwasting energy problems for future years. Semi-opened spaces as favorable and frequent spaces for people in urban areas affect strongly the quality of life and well-being of persons. Although the assessments of outdoor thermal comfort have been increased in recent years, the number of researches that primarily focused on human thermal comfort in semi-outdoor spaces is few. This article reviews the studies about semi-opened spaces have been executed in various climate conditions since late years. Furthermore, it explained the general assessment methods of the semi-outdoor thermal comfort

Thermal comfort differences between polycarbonate and opaque roofing material installed in bus stations of Malaysia

Bus shelter as a semi-outdoor space protectsindividuals from direct sun light, rain and wind. The roofing material of busstop has extreme influence on environmental and subjective conditions ofpersons within this space. In this study, the principal concentration isdistinguishing the differences between installation of Polycarbonate plasticroofing material and that of opaque protection cover as two widespread roofingmaterials in obtaining human thermal comfort in equatorial climate of Malaysia. Hence, two bus stops, one covered by Polycarbonate translucent plastic and onewith opaque concrete-based tile, were selected to evaluate their inner thermalcomfort condition by measurement of four main microclimatic parameters (i.e.air temperature, wind velocity, humidity and mean radiant temperature) as wellas subjective survey in a university campus using the Physiological EquivalentTemperature (PET) as thermal index. The study found that the Polycarbonateroofing material is not appropriate material for permanence in bus shelters ofMalaysia neither objectively nor subjectively comparing with opaque protectivecover. Additionally, it was revealed adoption greatly impacts individualthermal perception which should not be neglected in the examination of thermalcomfort in non-indoor spaces

Stages and elements affecting development of low carbon parks in Malaysia: an expert review

The purpose of this paper is to explore carbon performance at Malaysia Parks. This article aims to identify stages and elements that contribute carbon emission at parks based on expert review. The stages and elements were identified through document review process and experts validation. At the end of these phases, a list of carbon contributor at parks is proposed. Based on findings, (3) three stages (construction, operation and maintenance) and (24) twenty-four elements have been identified from the literature. Afterwards, data will be collected from two Landscape Architects (LA), two Subject Matter Experts (SME), and two Contractor Experts (CE). Fleiss kappa analysis was used to measure the percent agreement to determine interrater reliability. In order to measure the percent agreement among the data collectors, a matrix table has been created. The finding from this study it is reveals that parks also contributes carbon to environment. The findings of the study substantially highlighted that all experts agreed with the stages and elements that contribute carbon to the parks. The main contribution of this paper is to highlight stages and elements needed to be taken into account when creating a sustainability parks in Malaysia