173 Figure 5.6: Hourly profile of the average wind speed for the base case configuration in the four orientations; N-S, E-W, NE-SW and NW-SE. 174 Figure 5.7: Hourly profile of the average relative humidity for the base case configuration in the four orientations; N-S, E-W, NE-SW and NW-SE.
Introduction
Sustainability and the Built Environment Background
Thus, the main role of sustainable urban design is to optimize the form of urban development in order to reduce possible negative impacts on people's health, increase resource efficiency and improve productivity at the same time. Economically, sustainable output is the amount that can be consumed during the time period in continuous use until the end of the period (Basiago, 1999).
Climate Change
5 A sustainable neighborhood is a neighborhood that integrates the three pillars of sustainability 'Environment, Economy and Society'. Economically, those sustainable neighborhoods that provide all services and amenities will create independent livable, healthy communities that will have a positive effect on individuals and the entire society (Badland, 2014).
Pollution and Global Warming
Global warming, Urban Heat Island (UHI) and the increase in global air temperature are a result of the GHG emission effect. Therefore, cities must be designed in a way that minimizes GHG averages and pollution percentages.
Urban Planning and Design
Sustainable Urban Design
Sustainability at the urban level can be achieved by underestimating the three pillars of sustainability and the interrelation between them: environment, economy and social. All these compensations of urban designs should be designed in a way that provides vitality and comfort to improve people's lifestyle.
Liveable Environment
However, the study of urban living and the impact of urban design on people's health, well-being and productivity is ongoing. Parks and open and landscaped areas are elements of urban design that play an important role in providing a livable outdoor environment (Guzman and Harrell, 2014).
Climatic Urban Design
Livable outdoor environment and sustainable outdoor urban design, indoor environment and thermal performance of individual buildings (Lenzholzer et al., 2015). Zoning codes and urban planning regulations are generally established to control excessive shading of buildings from each other and to ensure fair access to sunlight and natural air for every building in any complex or neighborhood.
Urban Form and Urban Design Elements
Buildings Design and Geometry
Previous studies have demonstrated the effect of building design elements on the external and internal thermal performance of the built environment (Negendahl and Nielsen, 2015; Leiteet et al., 2015; Cruzet et al., 2016). 2015) studied the effect of the organization of the building within the complex and investigated the effects of different organizational plans on the energy efficiency of the building.
The Urban Canyon
On the other hand, Abohela, Hamza and Dudek (2013) investigated the effect of building roof shape on airflow and wind speed, and how this variable affects indoor thermal performance and energy consumption. Moreover, building facade materials, insulation, construction materials and the U-Value effect have a great impact on the energy performance of indoor spaces, and this fact has been presented in many studies (Alsemaa et al., 2016; Robati, 2017).
Buildings and Canyon Design Indicators
Gross Floor Area (GFA)" or "Built-up Area (BUA)" represents the amount of built-up area in the specific site or plot, and the GFA ratio or BUA ratio represents it. On the other hand, the 'floor factor that can be multiplied with the lot area to find the allowable FAR controls the compactness of the built-up area and is normally indicated in development codes and regulations to control it.
Dubai / UAE Urban Planning and Design
Urban Planning Codes and Mid-Rise Buildings
Most of these codes feature mid-rise residential buildings, but the configuration of this type, height, and orientation varies from code to code. This study will analyze medium-rise residential buildings to find the best configuration of this type of building that can help achieve minimum energy consumption.
The Significance of the Study
In addition, some published studies have examined the effect of urban design and configuration within the local context of the UAE and according to the weather characteristics of this region. This research will use computer software to simulate, analyze and evaluate urban configuration, and to identify the effect of urban geometry variables on outdoor microclimate parameters and indoor energy consumption.
The Research Questions
26 Climate change and environmental issues are among the top priorities on the UAE and Dubai agenda, and conducting this research will offer valuable results that could be considered by the urban planning and construction sector. Moreover, the findings of this research can be generalized to other world regions with the same weather characteristics and climate conditions.
Research Aim and Objectives
28 However, the previous findings related to the urban geometry variables and the effect of these variables on canyon microclimate parameters and building energy consumption will be illustrated in detail in the next chapter. The literature review, Chapter 2, will illustrate the past and recent findings related to urban configuration and urban geometry design.
The Research Focus and Limitations
The Research Framework
Furthermore, the suggested strategies for optimizing the urban geometry will be applied to the proposed scenarios developed. In addition, the best configurations that improve the parameters of the external microclimate and reduce the internal energy consumption will be presented.
Literature Review
The Microclimate and the Built Environment
However, the microclimate is the climatic conditions in the UBL and UCL in the built environment. It is still difficult to predict every single factor that contributes to microclimate conditions in the built environment.
Urban Heat Island UHI
Types of Urban Heat Island UHI
USHI is the average temperature of the horizontal surfaces, such as roofs of buildings, outdoor equipment. The second type of UHI is that within the Canopy Layer Heat Island (CLHI), which represents the area in the urban space between the buildings or the canyon space (Oke, 1976).
The Effect of the Urban Heat Island UHI
Hirano and Fujita (2012) conducted a field measurement study to determine the effect of UHI in Tokyo, Japan. Site function and building group have been shown to be another factor influencing the UHI effect.
Strategies for Mitigating the Effect of UHI
Canyon and Thermal Mass Exchange
Canyon Air Flow and Wind Velocity
Before illustrating the wind speed and air flow in the canyon space, the urban area's wind regime and wind pattern will be investigated. 45 material, the decisive factor that controls the behavior of the air flow in the canyon is the H/W ratio.
Canyon Air Temperature Distribution
The vortex moved to the top of the canyon and the air did not because of the high H/W ratio. On the other hand, the temperature of the floor surface is higher than the temperature in the center of the split room.
Canyon Surface Albedo
The Effect of Urban Geometry on Microclimate Parameters
A recent publication that examined the influence of urban geometry factors on environmental parameters of the built environment is a study published by Andreou (2014). The researcher presented the effect of urban geometry in the Mediterranean area. The researchers highlighted the influence of wind flow and relative humidity on heat transfer and presented the reverse.
Building Physics and Outdoor Microclimate Parameters
This reduction in CHTC at the bottom of the building is related to the small vortex effect in this area and the increased air residence time. Increasing the residence time of the air in the lower area reduces the temperature difference between this air and the surface of the building.
Ventilation and Air Quality in the Urban Canyon
Furthermore, the researchers assumed and analyzed different scenarios and found that the difference in effect between the parallel and the perpendicular wind is very small. The researchers simulated four scenarios of wind direction and speed to find the effect of each scenario on NO2 concentration.
Energy Performance of the Built Environment
This offers the opportunity to apply urban planning to reduce energy consumption on a large scale at an early design stage. On the other hand, Al Znafer (2014) studied the effect of SVF on the outdoor thermal comfort and the indoor energy consumption of an individual building in the city of Al Riyadh, Saudi Arabia.
The Effect of Urban Geometry on Building Energy Consumption
Cooling Plant Load and Energy Saving
The relative humidity is inversely related to the air's dry bulb showing the general relationship between both parameters. 75 Relative humidity is a measure of the actual amount of water carried by the air compared to cation at the saturation.
The UAE Urban Environment Researches and Studies
In addition, the researchers found that most simulated locations with an aspect ratio between 0.67 and 2.0 had light to gentle wind speeds. FLUENT (CFD) to achieve a more sustainable design. The researchers proved that the parametric design methodology produced a reduction of 1% - 8% in solar energy evaluation experiments.
The Urban Canyon in Hot Climate
The researchers used the SVF to represent the variation in urban geometry of the case study street. The researchers to evaluate the effect The climatic conditions of the city. to be an indicator of urban geometry variation and to study archers, they used the SVF to represent the urban geometry variation of the case study street.
Climatic Urban Design Strategies
Solar Effect
It will help to mitigate the effect of UHI and reduce energy consumption at city level. 87 Arnfield (1990) investigated the effect of H/W ratio and two orientations on the amount of sun received by canyon soils and building walls.
Wind Effect
Cao, Li, and Meng (2015) explored the effect of the canyon orientation on air speed and UHI. This configuration reduces the speed of the wind and reduces the air velocity in the canyon (Figure 2.53).
Summary of the Previous literatures on Urban Geometry and Gap Identification
On the other hand, an alternative arrangement of buildings is one of the urban geometry variables that has not been addressed or simulated using the software survey method. This research attempts to fill this gap and identify the effect of building height diversity and alternative configuration on indoor energy consumption at an urban scale.
Urban Geometry and the Research Selected Variables
In addition, few studies have examined the effect of microclimate parameters on indoor thermal performance and energy consumption at the urban level. Therefore, this study aims to fill this gap by investigating the effect of urban geometry variables, in particular the height diversity of buildings in the block, on microclimate parameters.
Methodology
Introduction
Chen and Edward Ng (2011) adopted the quantitative DEM data and the GIS software to generate a climate map. Furthermore, some studies have adopted the quantitative method and empirical data to develop a mathematical model that represents the relationship between the urban design factors and the environmental parameters (Ruiz-Arias et al., 2009; . Tarekegn et al., 2010).
The Most Employed Methodologies in Urban Planning Studies
Case study
In addition, the researchers approached the case study's qualitative method by using the Kowloon Peninsula in the southern area of Hong Kong for their study. The scale and location of the case study vary depending on the research goals and objectives (Djukic, Vukmirovic, and Stankovic, 2015).
Observation and Field Measurements
2013) compared six types of block typologies in the Netherlands to investigate the court's effect on energy efficiency. 2010) selected 15 housing archetypes in an area of London to evaluate the energy performance of housing, group of houses (Kavgic, 2010). 101 However, the time factor and the availability of the necessary instruments are some of the limitations of this method.
The Computer Simulation Software
In the published paper dealing with the effect of courtyards in Hijleh (2012), the IES-VE software used daylight factor and cooling load energy consumption. Muhaisen and Gadi (2005) VE software to investigate the effect of different proportions of the farm on solar energy and energy demand in Rome, Italy.
Methods of Exploring Energy Performance of Developments
The Research Methodology Selection
The Selected Case Study Description
The case study area is selected to collect the physical data required by the block model, which is additional. However, the area was built before the implementation of the Dubai Green Building Regulations and Specifications (2008). The community consists of two sets of medium-sized buildings.
The Computer Simulation Software Selection
The snapshot data generated from ENVI-Met will be edited as design data in the weather file in the IES-VE software. The capability, validity and accuracy of the IES-VE software had been proven in a number of publications.
Procedures of linking ENVI-met to IES-VE Software Data
In this research, this limitation was overcome by the maximum and minimum air temperature extracted from the ENVI-Met simulation software, and the humidity was represented by the wet bulb temperature. The maximum and minimum outdoor dry and wet bulb air temperature manually modified to the IES_VE weather file according to the extracted data of each configuration and orientation obtained from ENVI-Met.
The Computer Software Validation
The Validation of the Outdoor Microclimate Simulation Software ENVI-Met
Additionally, some plants are spread out in the main canyon/street between the buildings. The microclimate parameter chosen to validate the software is air temperature and one receptor is specified in the model to represent the exact location of the location station.
The Validation of the Indoor Thermal Performance Software IES-VE
The indoor air temperature of the villa for a given day and 12 hours is evaluated against th. The indoor air temperature of the cottage for one day and 12 hours of data is evaluated against the values obtained from the mode.
The Developed Proposed Scenarios Climatic Strategies
The simulation of the basic case study will be carried out on a complex or block of twenty residential buildings. The developed scenarios will be classified into three groups according to the selected urban geometry variables, each group.
The Proposed Urban Block Configurations
Planning and Regulations for Sustainable Form
137 However, it has been proven that medium-rise buildings and homes for the average population offer a higher level of sustainability (Marcus and Sarkissian, 1986; Heathcott, 2005; Fahmy and Sharples, 2009). The control, centralization and control in the planning can be displayed in the pattern planning; pattern planning is one of the planning strategies that can be applied to achieve the sustainable form.
Cluster Planning and the Urban Compactness Elements
The Methodological Approach to the Development of the Proposed Scenarios
Example of canyon (street) dimensions in Dubai regulation codes (Downtown Jebel Ali regulation code, Limitless, 2008). The developed configurations dimensions are selected based on the observation of the case study and review of the building codes and regulations followed n dimensions called the canyon dimensions presented in the development code of Downtown Jebel Ali.
The Cluster Urban Form
In the buildings and city regulations reviewed, the setback varies between 10m and 20m according to the use of this setback as a local street, driveway, alley, footbridge or landscaped area. 142 The recent architectural and urban planning trend of building a prototype villa community is a good example of the cluster form in urban planning.
The Development Criteria of the Proposed Groups
The height variation in the short axis is represented in the first group, while the height variation in the long axis is represented in the second group. The first group consists of four scenarios according to the proposed variation in building height in the short axis of the block, while the second group consists of six scenarios according to the height variation in the long axis of the block.
The Physical Characteristics of the Proposed Configurations
- The Base Case Configuration
- The First Group Configurations
- The Second Group Configurations
- The Third Group Configurations
146 Figure 4.7: The plan and the two sections A-A and B-B along the long and short axis of the base case. Similar to the base case and the two first groups, the block of buildings in the third group contains 24 buildings with a uniform height of G+5 and 24m.
Initial Input Data for Simulation Process
Preliminary Studies, the Dubai, UAE Climate
The weather in the UAE in general and in Dubai in particular is sunny most days of the year. The Wind Rose of Dubai again shows that the prevailing wind is the northwest wind with speeds that varied between 3 m/s - 9 m/s and it is rare that the wind speed rises above 12 m/s, although it has reached 15 m / s -20 m/s occasionally (Figure 4.14).
Micro climate Initial Conditions for Outdoor Simulation Software ENVI-Met
The initial input microclimate conditions to run the simulation process using the ENVI-Met software are illustrated. In the base case and all other group configurations, nine receptors are located in the main and side canyons of the developed model (Figure 4.20). All data will be collected at the level of 1.4 m from the ground surface at the receptor points (Figure 4.20). 4.21).
The Initial Conditions for the Indoor Thermal Performance Simulation Software
165 Therefore, the external microclimate data of the researched models will be extracted from the ENVI-Met software and will be used for the execution of the IES-VE software. 167 Table 4.2: Placement conditions in typical thermal file in IES-VE software for all.
The outdoor Thermal Performance of the Numerical Modelling
The Base Case Configuration Simulation Results
- Sky View Factor
- Air Temperature
- Wind Speed
- Relative Humidity
Figure 5.4 shows the SVF in the main canyons and alleys of the base case configuration. Although the SVF at the edge of the complex is higher than the SVF of the points in the center of the complex.
The First Group of the Proposed Configurations
Sky View Factor
Air temperature
Wind Speed
Relative Humidity
The Second Group of the Proposed Configurations
Sky View Factor (SVF)
Air Temperature
Wind Speed
Relative Humidity
The Third Group of the Proposed Configurations
Sky View Factor (SVF)
Air Temperature
Wind Speed
Relative Humidity
Summary of the Outdoor Thermal Performance for the Three Groups Configurations
The Configurations of the Best Outdoor Thermal Performance
Outdoor Thermal Performance and the Best Configurations
The Best Performance of the Base Case with Respect to the Block Orientation
The Best Performance of the First Group Configurations
The Best Performance of the Second Group Configurations
The Best Performance of the Third Group Configurations
The Effect of the Urban Block' Geometry and Orientation on the Outdoor Microclimate
The Heat Gain and Cooling Load of the Urban Block
The Indoor Heat Gain and Cooling Plant Load
Heat Gain and Cooling Plant Load of the Base Case
Heat Gain and Cooling Plant Load of the First Group Configurations
Heat Gain and Cooling Plant Load of the Second Group Configurations
Heat Gain and Cooling Plant Load of the Third Group Configurations
The Effect of Urban Geometry and Outdoor Microclimate Parameters on Cooling Load
Conclusion and Recommendations
The Effect Urban Geometry on Outdoor and Indoor Thermal Performance
The Effect of the Block Orientation
The Effect of the Height Diversity
The Effect of the Block Configuration
Urban Block Design and the Consideration for Climatic Design
Initial thermal and construction data of the typical configuration file used in IES-VE
The maximum and minimum microclimate parameters of the first group
The maximum and minimum microclimate parameters of the second group
The maximum and minimum reduction in air temperature averages of the third
