ArticlePDF Available

Abstract

Assessing human comfort outdoors is one of the key criteria in the design of building. One of the effective factors in creating comfort conditions is wind flow. The purpose of this study is to investigate the effect of urban blocks on wind flow for creating the comfortable condition. The ratio of buildings height to distance (H/W) and the orientation of buildings as the most important factors affecting wind flow were examined. The ratios of 0.5, 1, 1.5, and 2 were selected and orientations of 135° to 200° were examined. A residential complex in Tabriz was selected as a case study and weather information of the last 19 years (2002-2021) of Tabriz was extracted from the Meteorological Organization. Months of the year that were unfavorable in terms of comfort conditions were identified by using the Penwarden standard. Accordingly, January 6, 2021, was selected as one of the coldest days of the year, and to simulate different scenarios, Envi-met (4.4.5) software was used. The results show that the H/W ratios of 0.5 to 1 and the orientations of 200° to 185° and 135° are the most appropriate. In this research two important factors, H/W and their orientation were studied in a linear form. One of the limitations of the research is that only the comfort conditions in the outdoor environment of the buildings have been studied. Therefore, in future research, the arrangement of urban blocks to consume less energy inside buildings can be examined. Introduction Among the various factors of environmental comfort in outdoor space, wind flow has a great impact on the quality of urban spaces. In the 1970s, Lawson et al. reported the death of two elderly women due to sudden, strong winds around buildings. Wise et al. have conducted studies on shops that do not have customers due to wind conditions in the area. Various researches have been done on the shape and form of blocks, their ratio of height to their distance (H/W), orientations, and the effect of these factors on wind speed. However, most of this research has been done in areas with warm climates and cannot be generalized to other regions with different climates, and in most studies, the summer season has been analyzed and studied. A limited number of studies have examined the cold days of the year and cold climate. This research, in line with the research done in this field and with a more comprehensive look at the relationship between H/W ratio and also examining the orientation of buildings with more accurate angles, in the form of linear buildings, examines outdoor thermal comfort. This research has been done around one of the residential blocks in Tabriz, Iran with a dry climate and relatively hot summers and cold winters.
Journal of Environmental Studies
Vol. 48, No. 1, Spring 2022
Journal Homepage: www.Jes.ut.ac.ir
Print ISSN: 1025-8620 Online ISSN 2345-6922
The Relationship Between the Placement of Building Blocks and Wind
Flow at the Pedestrian Level
Mahsa Samadpour Shahrak1, Mehrdad Karimimoshaver1*
1 Department of Architecture, Faculty of Art and Architecture, Bu-Ali Sina University,
Hamedan, Iran
DOI: 10.22059/JES.2022.331141.1008229
Document Type
Research Paper
Received
September 23, 2021
Accepted
May 27, 2021
Abstract
Assessing human comfort outdoors is one of the key criteria in the design of building. One of the
effective factors in creating comfort conditions is wind flow. The purpose of this study is to
investigate the effect of urban blocks on wind flow for creating the comfortable condition. The ratio of
buildings height to distance (H/W) and the orientation of buildings as the most important factors
affecting wind flow were examined. The ratios of 0.5, 1, 1.5, and 2 were selected and orientations of
135° to 200° were examined. A residential complex in Tabriz was selected as a case study and weather
information of the last 19 years (2002-2021) of Tabriz was extracted from the Meteorological
Organization. Months of the year that were unfavorable in terms of comfort conditions were identified
by using the Penwarden standard. Accordingly, January 6, 2021, was selected as one of the coldest
days of the year, and to simulate different scenarios, Envi-met (4.4.5) software was used. The results
show that the H/W ratios of 0.5 to 1 and the orientations of 200° to 185° and 135° are the most
appropriate. In this research two important factors, H/W and their orientation were studied in a linear
form. One of the limitations of the research is that only the comfort conditions in the outdoor
environment of the buildings have been studied. Therefore, in future research, the arrangement of
urban blocks to consume less energy inside buildings can be examined.
Keywords: Outdoor thermal comfort, wind speed, building orientation, H/W ratio
* Corresponding Author: Email: mkmoshaver@basu.ac.ir
Journal of Environmental Studies
Vol. 48, No. 1, Spring 2022
16
Introduction
Among the various factors of environmental comfort in outdoor space, wind flow has a great impact
on the quality of urban spaces. In the 1970s, Lawson et al. reported the death of two elderly women
due to sudden, strong winds around buildings. Wise et al. have conducted studies on shops that do not
have customers due to wind conditions in the area. Various researches have been done on the shape
and form of blocks, their ratio of height to their distance (H/W), orientations, and the effect of these
factors on wind speed. However, most of this research has been done in areas with warm climates and
cannot be generalized to other regions with different climates, and in most studies, the summer season
has been analyzed and studied. A limited number of studies have examined the cold days of the year
and cold climate. This research, in line with the research done in this field and with a more
comprehensive look at the relationship between H/W ratio and also examining the orientation of
buildings with more accurate angles, in the form of linear buildings, examines outdoor thermal
comfort. This research has been done around one of the residential blocks in Tabriz, Iran with a dry
climate and relatively hot summers and cold winters.
Materials and Methods
The study site is located in a residential area of Tabriz city. Tabriz (38.12°N, 46.24°E) is a metropolis
in the Azerbaijan region of Iran and is the capital of East Azerbaijan Province. Tabriz has a population
of over 1.7 million (2016). Its climate is dry steppe and enjoys a mild and fine climate in spring, a dry
and semi-hot in summer, a humid and rainy in autumn, and snowy cold in winter. The prevailing wind
is from east to west. The average annual temperature is 12.6°C (54.7 °F). It's elevation ranges between
1,350 and 1,600 meters (4,430 and 5,250 ft) above sea level.
One of the pioneers who prepared a graph to predict pedestrians' outdoor comfort zone is Penwarden.
In 1975, he introduced his graph according to his comprehensive field studies in the UK. This graph
that had been used for several years shows the needed periods for sunshine, shade, and wind according
to the metabolic rate of the pedestrian with suitable seasonal clothes. For this reason, in this study, the
Penwarden index was used to identify months of the year when conditions are unfavorable for
pedestrians. Thus, January was identified as the worst month of the year in terms of thermal comfort.
Also, February and December do not have favorable conditions. As a result, January 6, 2021, was
selected as one of the coldest days of the year, and the effect of building blocks on wind flow in winter
was investigated (Fig1).
Figure 1: Status of different months of the year in Penward index, right: shadow, left: sunny
The Relationship Between the Placement of ...
Mahsa Samadpour Shahrak, Mehrdad Karimimoshaver
17
ENVI-met software (4.4.5) was used to simulate the surrounding environmental conditions. The
information entered in the software can be seen in Table 1.
Table 1: Information and data entered in ENVI-met software
Discussion of Results:
The comparison between the H/W ratio and wind speed shows that with increasing height above
ground level and this ratio, wind speed also increases.
The results show that in winter, with increasing the H/W ratio, the wind speed also increases. The
average of wind speed at the ratios H/W=0.5 and H/W=1 is close to each other and increases when this
ratio changes to H/W=1.5 and H/W=2. Therefore, H/W=0.5 to 1 ratio is suitable for design in this
climate, and increasing this ratio can disrupt outdoor comfort conditions. This study agrees with
researches that have examined this ratio in different climates in winter.
Also about the orientation of the blocks, Oke, Jin et al. concluded that in the linear pattern the angle
between the wind direction and the axes of the blocks are inversely related to the wind speed. As the
angle between the wind direction and the axes of blocks increases, the wind speed decreases. Studies
in the subtropical climate of Tunisia's Mediterranean climate in summer, the Brazilian subtropical
climate, the temperate climate of the Netherlands in summer, the very cold climate of China
considered North-South (NS) orientation as the most appropriate one. Rizk-Hegazy et al. compare the
four directions of 70,160,100,10 degrees from the north in the hot and dry climate of Saudi Arabia and
consider 160 degrees clockwise from the north as the most suitable option. Also, studies conducted in
the hot and dry climate of Algeria, hot and humid climate of Brazil are considered northeast-
southwest(NE-SW), Northwest-Southeast (NW-SE) as the best orientation. This study, which
examines eight angles, shows that the angles of 200° to 185° and 135° have a lower average wind
speed, so it creates favorable conditions at the site, and angles of 175°, 165°, 155°, and 145° have
higher average wind speeds and cause unfavorable conditions in the environment.
Conclusions:
The present study evaluates wind speed as the most important factor affecting thermal comfort
conditions around residential blocks in a linear manner. Assuming that the height, distance, and
orientation of the blocks are the factors that can affect wind speed. In this study, an arid climate with
relatively hot summers and cold winters was selected as the study area. By using the Penwarden index,
and comparing temperature and wind speed, the months of the year with the worst comfort conditions
were identified. January was selected as the month that needs to be studied more closely to improve
environmental conditions. Examining the number of changes that occur in the average wind speed in
changing the H/W ratio, it can be concluded that with increasing H/W ratio, the average wind speed
has an upward trend. And, ratios of H/W=0.5 to 1 can be considered the most appropriate ratio.
Concerning the orientation of the buildings, it shows that the average wind speed was the lowest at an
46.24°E, 38.12°N
Geographical Location
Tabriz, East Azerbaijan Province, Iran
Name of the area
2021.01.06
Date
x-Grids=50, y-Grids=50, z-Grids=40
Model Dimensions
dx=4,dy=4,dz=5
Size of grid cell in meter
9 AM-8 PM, 11hours
Simulation time
Min: -9°c, Max: 0.6°c
Temperature
2.9m/s
Wind speed
70°(North-East)
Wind direction
58%
Relative humidity
Albedo: 0.4, Thermal capacity: 2.08 [J m3 K1] × 106,
Thermal Conductivity: 1.63 [W m1 K1]
Pavement material: Cement Concrete
Thickness: 15cm, U-value: 2.54 (W/ m2K)
Building envelope: Cement Walls
Journal of Environmental Studies
Vol. 48, No. 1, Spring 2022
18
angle of 200°, and with the change of the direction of the buildings clockwise to the north, the average
of this index increased and reached the highest value at an angle of 165° then it decreases. Therefore,
angles of 200° to 185° and 135° are the most favorable, and angles of 175° to 145° are not suitable. In
this research two important factors, H/W and their orientation were studied in a linear form. One of the
limitations of the research is that only the comfort conditions in the outdoor environment of the
buildings have been studied. Therefore, in future research, the arrangement of urban blocks to
consume less energy inside buildings can be examined.





 




(H/W)

°°



H/W
°°°
H/W






LawsonPenwarden

Wise


Karimimoshaver



Metje



Müller

mkmoshaver@basu.ac.ir Email:
DOI: 10.22059/JES.2022.331141.1008229
DOR: 20.1001.1.10258620.1401.48.1.2.5

 

Kim









(Hegazy and Qurnfulah, 2020)
Achour-YounsiKharrat
H/W


HegazyQurnfulah



Shui



Liu





Lin





Masnavi






Javanroodi






Nasrollahi




EyniTaban




RozatiGhanbaran








Karimimoshaver





















(H/W)








































°°



 
¸¸














WRPLOT
Lakes Environmental




WRPLOT



























WRPLOT
Station Elevation
Lon
Lat
Station ID
Data Fields (2002-2021)

 E
N






Farsicad.com




Ashrae, 1997






Penwarden and Wise, 1975









 








(0.5 clo)

(1.0 clo)












(1.5 clo)


























  











(Taleghani et al., 2015





u/t+ui(u/xi)=-p/x+Km(2u/x2i)+ f(v
vg)- Su
v/t+ ui(u/xi)=-p/y+Km(2v/x2i)+ f(u
ug)- Sv
w/t+ ui(w /xi)=-p/z +Km(2 w /x2i)+
g (z) / - Ɵref(z))- S w
f ( = 104 
'pƟ
ZƟref

p

W


u
x
v
y
w
z
0


(ui= u,v,w i=1,2,3)Su,
Sv , Sw







Wang
and Akbari, 2016; Taleghani and Berardi, 2018




 




 





 




ampm






°N°E

Tabriz, East Azerbaijan Province, Iran



x-Grids=, y-Grids=, z-Grids=

dx=,dy=,dz=



°c

°c

°c







]
1
K
3
m [J 2.08 capacity: Thermal 0.4, Albedo: ]
1
K
1
m [W 1.63 Conductivity: Thermal ,
6
10 ×

K)
2
m (W/ 2.54 value:-U 15cm, Thickness:

Kasmaei









H/W
H/W







H/W


H/W=0.5

H/W=2
H/W=0.5H/W=1
H/W=1.5H/W=2






H/W









 

H/W






 

H/W=0.5,1







(Johansson et al., 2006)
(Martinelli and Matzarakis, 2017)



H/W
Jamei
and Rajagopalan, 2017Nasrollahi et)
(al., 2017H/W



°°
°°

°
°


°

°

°
°°




°°

°°






 
  


°°

°°

 °
 






OkeJin


 
Oke, 1988, Jin et al, 2017




(E-W)(N-S)
(NE-SW)NW-)
(SE
Achour- Younsi and Kharrat, 2016, )
Martins et al., 2012, Nasrollahi et al., 2017,
(Taleghani et al., 2015, Hegazy and Qurnfulah, 2020
Achour-Younsi and)
(Kharrat, 2016Martins et)
(al., 2012
(Taleghani et al., 2015)
(Liu et al., 2019)(N-S)
 HegazyQurnfulah








(Lin et al., 2019)
(NW-SE)Nasrollahi




°°
°°
°°
°°






 











H/W

H/W





°
°°°
°
°°°










1 Height to Width
2 WCET (Wind Chill Equivalent Temperature)
3 NavierStokes
4 BoussinesqApproximation

Achour-Younsi, S., & Kharrat, F. (2016). Outdoor thermal comfort: impact of the geometry of an
urban street canyon in a Mediterranean subtropical climatecase study Tunis, Tunisia.
Procedia-Social and Behavioral Sciences, 216, 689-700.
Ashrae, A.H.-F., 1997. American Society of Heating, Refrigerating and Air- Conditioning Engineers.
Inc. Atlanta.
Eyni, A., & Taban, M. (2019). Evaluation of the effect of physical structure on the wind flow pattern
in urban environments (case study: Siyah-Poshan and Gozare Shahi neighborhoods in Ghaleh
district of Dezful). Environmental Sciences, 17(2), 155-172.
Hegazy, I. R., & Qurnfulah, E. M. (2020). Thermal comfort of urban spaces using simulation tools
exploring street orientation influence of on the outdoor thermal comfort: a case study of Jeddah,
Saudi Arabia. International Journal of Low-Carbon Technologies, 15(4), 594-606.
Jamei, E., & Rajagopalan, P. (2017). Urban development and pedestrian thermal comfort in
Melbourne. Solar Energy, 144, 681-698.
Javanroodi, K., Mahdavinejad, M., & Nik, V. M. (2018). Impacts of urban morphology on reducing
cooling load and increasing ventilation potential in hot-arid climate. Applied energy, 231, 714-
746.
Jin, H., Liu, Z., Jin, Y., Kang, J., & Liu, J. (2017). The effects of residential area building layout on
outdoor wind environment at the pedestrian level in severe cold regions of China. Sustainability,
9(12), 2310.



Johansson, E. (2006). Influence of urban geometry on outdoor thermal comfort in a hot dry climate: A
study in Fez, Morocco. Building and environment, 41(10), 1326-1338.
Karimimoshaver, M., Hajivaliei, H., Shokri, M., Khalesro, S., Aram, F., & Shamshirband, S. (2020).
A model for locating tall buildings through a visual analysis approach. Applied Sciences,
10(17), 6072.
Karimimoshaver, M., & Shahrak, M. (2022). The effect of height and orientation of buildings on
thermal comfort. Sustainable Cities And Society, 79, 103720. doi: 10.1016/j.scs.2022.103720
Karimimoshaver, M., Khalvandi, R., & Khalvandi, M. (2021). The effect of urban morphology on heat
accumulation in urban street canyons and mitigation approach. Sustainable Cities And Society,
73, 103127. doi: 10.1016/j.scs.2021.103127
Kasmaei, M. (2003), Climate and architecture, Khak
Kim, H., Lee, K., & Kim, T. (2018). Investigation of pedestrian comfort with wind chill during winter.
Sustainability, 10(1), 274.
Lawson, T. V., & Penwarden, A. D. (1975). The effects of wind on people in the vicinity of buildings.
4th Int. In Conf. Wind Effects on Buildings and Structures, Heathrow.
Lin, Y., Jin, Y., & Jin, H. (2019). Field study on the microclimate of public spaces in traditional
residential areas in a severe cold region of China. International journal of environmental
research and public health, 16(16), 2986.
Liu, Z., Jin, Y., & Jin, H. (2019). The effects of different space forms in residential areas on outdoor
thermal comfort in severe cold regions of China. International journal of environmental
research and public health, 16(20), 3960.
Martinelli, L., & Matzarakis, A. (2017). Influence of height/width proportions on the thermal comfort
of courtyard typology for Italian climate zones. Sustainable Cities and Society, 29, 97-106.
Martins, T. A. T. H. I. A. N. E., Adolphe, L., & Krause, C. L. Á. U. D. I. A. (2012, November).
Microclimate effects of urban geometry on outdoor thermal comfort in the Brazilian tropical
semi-arid climate. In Conference opportunities, limits e needs towards and environmentally
responsible architecture.
Masnavi, M. R., Laghai, H. A., & Ghobadi, N. (2012). Eco design and the optimization of passive
cooling ventilation for energy saving in the buildings: a framework for prediction of wind
environment and natural ventilation in different neighborhood patterns. In Design for innovative
value towards a sustainable society (pp. 177-182). Springer, Dordrecht.
Metje, N., Sterling, M., & Baker, C. J. (2008). Pedestrian comfort using clothing values and body
temperatures. Journal of Wind Engineering and Industrial Aerodynamics, 96(4), 412-435.
Müller, N., Kuttler, W., & Barlag, A. B. (2014). Counteracting urban climate change: adaptation
measures and their effect on thermal comfort. Theoretical and applied climatology, 115(1), 243-
257.
Nasrollahi, N., Hatami, M., Khastar, S. R., & Taleghani, M. (2017). Numerical evaluation of thermal
comfort in traditional courtyards to develop new microclimate design in a hot and dry climate.
Sustainable Cities and Society, 35, 449-467.
Oke, T. R. (1988). Street design and urban canopy layer climate. Energy and buildings, 11(1-3), 103-
113.
Penwarden, A. D., & Wise, A. F. E. (1975). Wind environment around buildings. HM Stationery
Office.
Rozati, S. H., & Ghanbaran, A. (2014). Comfort Evaluation in Urban Open Spaces Based on Wind
Comfort Criteria, Case Study: Isfahan. Environmental Sciences, 12(4).

 
Shui, T., Liu, J., Yuan, Q., Qu, Y., Jin, H., Cao, J., & Chen, X. (2018). Assessment of pedestrian-level
wind conditions in severe cold regions of China. Building and environment, 135, 53-67.
Taleghani, M., & Berardi, U. (2018). The effect of pavement characteristics on pedestrians’ thermal
comfort in Toronto. Urban climate, 24, 449-459.
Taleghani, M., Kleerekoper, L., Tenpierik, M., & Van Den Dobbelsteen, A. (2015). Outdoor thermal
comfort within five different urban forms in the Netherlands. Building and environment, 83, 65-
78.
Wang, Y., & Akbari, H. (2016). The effects of street tree planting on Urban Heat Island mitigation in
Montreal. Sustainable Cities and Society, 27, 122-128.
Wise, A. F. E. (1971). Effects due to groups of buildings. Philosophical Transactions of the Royal
Society of London. Series A, Mathematical and Physical Sciences, 269(1199), 469-485.
ResearchGate has not been able to resolve any citations for this publication.
Article
Full-text available
Urban heat island (UHI) has proved to have an important effect in urban microclimate of large cities. In particular, the materials used for the pavements of urban spaces and sidewalks affect pedestrians' comfort significantly. Dark materials store solar radiation during the day and re-radiate it overnight. Reversely, cool materials, given their high albedo, are often proposed for mitigating UHI issues. This paper focuses on the effect on the outdoor thermal comfort of different materials in a main urban square in Toronto. The study is performed at the neighborhood scale, using the high resolution software ENVI-met. Simulations done for a summer heat wave in 2015 allowed predicting the maximum effect of pavements with surfaces having different albedo. The physiological equivalent temperature (PET) is used to assess the pedestrians' thermal comfort. The results show the relative effectiveness of different pavement materials. In particular, thermal comfort evaluations are reported to assess the microclimate benefits of bright marbles over black granites.
Article
Full-text available
Tall buildings have become an integral part of cities despite all their pros and cons. Some current tall buildings have several problems because of their unsuitable location; the problems include increasing density, imposing traffic on urban thoroughfares, blocking view corridors, etc. Some of these buildings have destroyed desirable views of the city. In this research, different criteria have been chosen, such as environment, access, social-economic, land-use, and physical context. These criteria and sub-criteria are prioritized and weighted by the analytic network process (ANP) based on experts' opinions, using Super Decisions V2.8 software. On the other hand, layers corresponding to sub-criteria were made in ArcGIS 10.3 simultaneously, then via a weighted overlay (map algebra), a locating plan was created. In the next step seven hypothetical tall buildings (20 stories), in the best part of the locating plan, were considered to evaluate how much of theses hypothetical buildings would be visible (fuzzy visibility) from the street and open spaces throughout the city. These processes have been modeled by MATLAB software, and the final fuzzy visibility plan was created by ArcGIS. Fuzzy visibility results can help city managers and planners to choose which location is suitable for a tall building and how much visibility may be appropriate. The proposed model can locate tall buildings based on technical and visual criteria in the future development of the city and it can be widely used in any city as long as the criteria and weights are localized.
Article
Full-text available
At present, the environmental quality of urban regions and outdoor spaces has turn out to be one of the main issues facing both climatologists and designers, which could be identified through their research outcomes. It is argued that the urban configuration affects the micro-climate of the urban outdoor spaces. The street's orientation form was identified as an element, which impacts the urban environment with regards of receiving passive solar, solar radiation and reflection against urban absorption, wind flow and the possible urban cooling techniques. The key purpose of this study is to look into the urban configuration factors affecting the human thermal outdoor comfort in Jeddah city as an example of hot humid climate regions. To accomplish its aim, the research is divided to two sections. The first one illustrates the problem of the research, then generally reviews the literature associated with the outdoor human thermal comfort; in addition, it discusses the relationship between street orientation and micro-climate. The second section highlight the assessments carried out between four different orientations of urban streets from two different districts in Jeddah city, using ENVI-met software. The research adopts three environmental variables to be examined, namely air temperature, wind speed, relative humidity together with pedestrian thermal comfort as indicators for predicted mean vote, during summer and winter seasons. The outcomes of the comparison assist to identify decisions related street networks to achieve the desirable human outdoor thermal comfort in such an urban environment.
Article
Full-text available
In the context of global climate change and accelerated urbanization, the deterioration of the urban living environment has had a serious negative impact on the life of residents. However, studies on the effects of forms and configurations of outdoor spaces in residential areas on the outdoor thermal environment based on the particularity of climate in severe cold regions are very limited. Through field measurements of the thermal environment at the pedestrian level in the outdoor space of residential areas in three seasons (summer, the transition season and winter) in Harbin, China, this study explored the effects of forms and configurations of three typical outdoor spaces (the linear block, the enclosed block, and the square) on the thermal environment and thermal comfort using the Physiologically Equivalent Temperature (PET). The results show that the thermal environment of all outdoor space forms was relatively comfortable in the transition season but was uncomfortable in summer and winter. The semi-enclosed block with a higher sky view factor (SVF) had a higher thermal comfort condition in summer and winter. The linear block with higher buildings and wider south–north spacing had a higher thermal comfort condition in summer and winter. When the buildings on the south side were lower and the south–north spacing was wider, the thermal environment of the square was more comfortable in winter.
Article
Full-text available
As residential environment science advances, the environmental quality of outdoor microclimates has aroused increasing attention of scholars majoring in urban climate and built environments. Taking the microclimate of a traditional residential area in a severe cold city as the study object, this study explored the influence of spatial geometry factors on the microclimate of streets and courtyards by field measurements, then compared the differences in microclimate of distinct public spaces. The results are as follows. (1) The temperature of a NE-SW (Northeast-Southwest) oriented street was higher than that of a NW-SE (Northwest-Southeast) oriented street in both summer and winter, with an average temperature difference of 0.7–1.4 °C. The wind speeds in the latter street were slower, and the difference in average wind speed was 0.2 m/s. (2) In the street with a higher green coverage ratio, the temperature was much lower, a difference that was more obvious in summer. The difference in mean temperature was up to 1.2 °C. The difference in wind speed between the two streets was not obvious in winter, whereas the wind speed in summer was significantly lower for the street with a higher green coverage ratio, and the difference in average wind speed was 0.7 m/s. (3) The courtyards with higher SVF (sky view factor) had higher wind speeds in winter and summer, and the courtyards with larger SVF values had higher temperatures in summer, with an average temperature difference of 0.4 °C. (4) When the spaces had the same SVF values and green coverage ratios, the temperature of the street and courtyard were very similar, in both winter and summer. The wind speed of the street was significantly higher than the courtyard in summer, and the wind speed difference was 0.4 m/s.
Article
Full-text available
Cooling buildings in urban areas with hot-arid climate put huge loads on the energy system. There is an increasing trend in urban energy studies to recognize the urban design variables and parameters associated with the energy performance of buildings. In this work, a novel approach is introduced to investigate the impacts of urban morphology on cooling load reduction and enhancing ventilation potential by studying a high-rise building (target building), surrounded by different urban configurations, during six warm months of the year in Tehran at four major sections including: (1) generating 1600 urban case studies considering three parameters (Urban Density, Urban Building Form, and Urban Pattern) and modelling the urban morphology of Tehran based on a technique namely "Building Modular Cells" , (2) validation study of CFD simulation of the wind flow around buildings, (3) calculating the average cooling load and wind flow at the rooftop of the target building, and (4) investigating sixteen best urban configurations with the lowest cooling load and highest ventilation potential. Results indicate that urban morphology has a notable impact on the energy consumption of buildings, decreasing cooling load and increasing ventilation potential more than 10% and 15% respectively, compared to the typical cases. This work also proposes design solutions for architects and urban designers, based on Top 100 configurations (out of 1600), for improved energy performance and better ventilation of buildings in urban areas.
Article
The purpose of this study is to investigate the climatic and natural capabilities to optimize open spaces. Two physical indicators, the ratio of the height of buildings to their distance from each other (H/W) and the orientation of buildings towards the street, were examined as the most critical factors affecting outdoor comfort conditions. Regarding the aspect of H/W, ratios of 0.5, 1, 1.5, and 2 were selected, which represent buildings with 3 to 13 floors at a distance of 20 meters from each other. Also, about the orientation factor, angles of 135° to 200° clockwise from the north were examined. This study was conducted in Tabriz with a dry climate, cold winters, and relatively hot summers. For simulating different scenarios, Envi-met and Rayman were used. Three factors of air temperature (Ta), mean radiant temperature (Tmrt), and physiological equivalent temperature index (PET) were examined as essential factors of thermal comfort. For validation, local and field data on a simulated day were compared with the data extracted from the software. The results show that considering both summer and winter, the ratio of H/W=1.5 and the angle of 135° from the north are the most suitable.
Article
The configuration of urban street-canyons, especially the ratio of the height of the buildings to the street width (H/W) and length to width (L/W), plays an essential role in directing and dispersion of wind flow and consequently affects changes in air temperature and urban heat islands (UHI). Despite many studies examining the aspect ratio of street-canyons, failure to follow these ratios from a specific order and organization and the lack of an optimal range for urban design is a gap seen in these studies. In addition, if the H/W exceeds a certain range, the results will change significantly and sometimes in reverse. Therefore, this paper simulates a residential town using CFD calculations in ANSYS-CFX 18. In two different scenarios (each scenario has four modes), wind flow and temperature changes were evaluated to find the optimal value of H/W and L/W. The analysis of changes in the three factors of wind velocity, temperature, and pressure show that the ratios H/W =1 and L/W=2 are the most suitable conditions for temperature reduction and UHI control. In addition, a sensitivity analysis confirms the generalizability of the obtained ratios to other fields with different temperature conditions and wind speeds.