Studying the Microclimatic Effects of Trees on Thermal Performance of Residential Buildings in the Gaza Strip

Abstract

A growing interest among architects and scientists to achieve energy-efficient buildings complies with increased energy demand and the international goals of creating environment-friend buildings. The Gaza strip is one of the most growing population densities. Hence, as the population density increases rapidly, the populated built area increases too, resulting urban summer hotter and winter colder. The effects of urban heat islands, rising consumer standards through air-conditioning and electrical gadgets in buildings, and thus rising man-made CO2 emissions contribute to environmental damage, public health threatening, and economic crisis. Furthermore, the Gaza Strip suffers from energy sources shortage and in the same time it faces the most serious electricity problem. Accordingly, passive solar design techniques in modern buildings have been utilized to achieve thermal comfort by decreasing the dependence on fossil fuels as much as possible. One of the passive solar design methods is choosing suitable tree configurations near buildings. Urban trees play an important role in moderating urban climate and reducing energy demand by shading buildings in summer, thus reducing the need for energy intensive air conditioning, cooling the surrounding air though evapo-transpiration and other benefits. The current study investigated the effect of trees shade on the thermal performance of residential buildings in the Gaza Strip and highlighted the best trees configurations. Accordingly, the best tree configurations (trees geometries, crown size, locations near building, and numbers) have been targeted to achieve thermal comfort in both summer and winter seasons. The analytical approach using computer simulation tools namely “DESIGNBUILDER and ECOTECT” were utilized to carry out the study. The research concluded that choosing the optimum trees configuration depends on many factors including site orientation, building shape, soil type, tree shape and foliage, and the number and location of trees. It was found that the value of cooling loads reduction as a result of changing deciduous trees form can be ordered from the highest to the lowest as follow: vase tree, high trunk umbrella, rounded and oval. It was concluded also that shading the east side of building provides the maximum energy savings in summer and winter followed by west side and south side consequently. However, west side is the most important to shade because the need of tree shading afternoon is more important than that in the early morning. On the other side, the closer tree and larger to home, the more shade it provides. Besides that, it was observed that choosing the optimum trees number and locations can reduce annual energy consumption by about 10%-18%. The effect of trees on reducing energy loads increases as building orientations change from 0-North to 45-North. Also, North-South street orientation is more affected by trees shade in summer than other orientation, while East-West street orientation is more affected by trees shade in winter. Therefore, the research recommended choosing trees configurations according to scientific standards that comply with energy consumption reduction and environment conditions. It is important to take into consideration trees types, locations, maturity size, height and number when using trees.