Urban Cool Islands (MArch)

URBAN COOL ISLANDS

EMTECH 2015

Shahad Abdulmonem & Abhilasha Porwal

Urban Cool Islands reverse the efect of heat islands by the designed use of a combination of water and vegetation based on principles of evaporative cooling and shading.

Architectural Association School of Architecture

Program: Emergent Technologies & Design

Term: 2014/2015

Name: Shahd Abdelmoneim, Abhilasha Porwal

Title: Urban Cool Islands

Course Title: Master of Architecture

Course Tutors: Michael Weinstock, George Jeronimidis Evan Greeberg, Mehran Gharleghi

Date: 06-02-2015

Declaration:

“I certify that this piece of work is entirely my/our own and that any quotation or paraphrase from the published or unpublished work of others is duly acknowledged.”

Signature:

Shahd Abdelmoneim Abhilasha Porwal

Acknowledgements

Our sincere gratitude to Mike and George - your relentless eforts and feedback are invaluable. We would like to thank Evan, Mehran, and Wolf for their inspiration and support throughout this thesis and course.

We would also like to thank our families and friends. Your continuous love and support are the pillars on which we stand.

Abstract

For cities in extreme hot, arid climates thermal comfort is perhaps the most prominent factor that dictates the use of outdoor space. While vernacular cities arranged themselves in ways to ameliorate heat, they failed to accommodate technology and modern modes of transport. Therefore, this model was abandoned and cities were planned based on foreign principles derived from milder climates.

Thus, contemporary cities in this region sufer from an exceptionally severe amplifcation of heat in the form of Urban Heat Islands (UHI), and because temperatures are regularly above 40°C this has a catastrophic impact on outdoor space.

To mitigate the efect of the UHIs, this research investigates methods based on evaporative cooling and shading within cities located in the hot, arid region. This is carried out through a calibration between building arrangement, vegetation, and water. Further, it explores the scale and morphology at which outdoor spaces can occur based on what thermal comfort allows. As park is to mild climates, Urban Cool Island is to hot ones.

“As cities are a refection of our culture, a universal approach to urban development seems an absurd concept. Urban ecology and culture are directly linked to climatic conditions. In the past these have been powerful drivers in the development of both city layouts and individual building typologies, creating unique urban or architectural features such as shaded streets, protected squares and courtyards that greatly contribute to the identity of the city they are creating and infuence the lives of their inhabitants.”

- Wolf Mangelsdorf

Domain

Areas of Concern & State-of-the-Art

Climatic Conditions

General Climatic Characteristics of Hot, Arid Regions

According to the Koppen climate classifcation, most regions that fall under the hot and arid region are located 30 degrees north or south of the Equator. Areas that usually fall under this climatic band are Central/Western Asia, the Middle East, North/South America, Africa, and Central/Northwestern Australia (Corsi 2004). See Figure 1.3.

The general pattern in these regions can be characterised by low moisture levels in the air and soil, and high day temperatures during the summer. Maximum temperatures during the summer range from 35°C to 50°C, with humidity levels rarely exceeding 50%. See Figure 1.4. Minimum summer temperatures fuctuate between 25°C and 30°C. High temperatures are mainly due to the high solar incidence angle on areas in the lower latitudes, in addition to the lack of cloud cover which otherwise refect, absorb, or scatter solar radiation. Direct solar radiation is as intense as the radiation refected from the light colored land, amplifed by the high glare from refective buildings. As a result, ground surface temperature can reach up to 70°C (Peell 2007).

Figure 13

Koppen

Classifcation: location of regions that fall within the hot, arid band. http://upload. wikimedia.org/ wikipedia/commons/

Phoenix, Arizona, Usa

Tehran, Iran

Khartoum, Sudan

Riyadh, Saudi Arabia

Kuwait City, Kuwait Sanaa, Yemen

Alice Springs, Australia

Climatic Conditions of Cities in the Hot, Arid Region

Numerical data on general climatic conditions.

Data obtained from IISD.

Figure 1.4

Geographic Conditions

Aridity can be expressed using the Climatic Aridity Index; a ratio of precipitation over the potential of evapotranspiration (Zomer, 2008). Desert regions typically receive less than 250 mm of rainfall annually, with an average Aridity Index of 0.2. Some regions may receive more than 250 mm of precipitation per year, but because of scorching temperatures and thus a high rate of evapotranspiration the region loses more water than it gains.

Warm winds high in velocity increase the already extreme ambient temperature. This coupled with low precipitation rates means low soil moisture and quality, and thus low vegetation cover and a high percentage of nonarable land. See fgure 1.7. This also contributes to dust storms, which are common in the region.

Furthermore, freshwater is scarce in these regions leading to very high water stress levels. Simultaneously, these regions are the same ones that consume the most freshwater, which usually is obtained through desalination. See Figure 1.6. Extreme heat, aridity, and the lack of freshwater combine to form some of the harshest conditions in the world, making it a constant struggle to live with the urban heat generated by the contemporary city planning and a growing population.

Figure

Figure 1.6

Data from KISR, Water Research Center.

Fresh Water Availability vs. Consumption

Figure 1.8

Street Views in Bahrain, Kuwait and Shibam.

http://thefabweb. com/86422/30best-aerialpictures-of-themonth-march17th-to-april15th-2013/

Vernacular Urban Fabric

Precedents from Vernacular Cities in the Region

Figure 1.9

Passive Cooling in a Typical Courtyard in Kuwait.

http://i19. photobucket.com/ albums/b169/ ktland/daa7f0d0. jpg

2.0

Aerial View of Shibam, Yemen.

http://wgaw. blogspot. co.uk/2009/12/ old-bahrain.html

Figure 2.1

Aerial View of Ghadames, Libya.

national geographic.com/ photography/ photo-of-the-day/ ghadames-aerialsteinmetz/

In climates where heat records are the highest in the world, it is imperative for distances to be walkable whilst minimizing radiation.

Vernacular urban tissue samples of cities belonging to such climates show that prior to controlled thermal indoor environments, streets were on average no more than 5 meters wide and courtyards occurred as often as every 20 meters. See vernacular tissue samples.

Water bodies and trees were also strategically placed to alleviate heat in the immediate outdoor area. See Figure 1.9. Wind catchers and water fountains were also placed to improve ventilation and cool the air.

Materials were also typically made of a mixture of adobe, stone, and any available material. These materials were non-refective and did not radiate heat. Thus, the surrounding buildings did not heat the streets maximizing the cooling efect of shade.

The harsh climatic conditions resulted in compact cities, where relatively large spaces were reserved for important (i.e. religious, judicial) functions where gatherings on a larger level would occur.

Figure

Vernacular Tissue Samples

Extracting Physical Parameters of 100m x 100m samples from Shibam, Muharraq, and Kuwait City

Figure 2.7

100x 100 patch sample of Muharraq, Bahrain.

Figure 2.8 Radiation analysis.

Figure 2.9

Public space distribution in Muharraq, Bahrain.

Figure 3.0 Extracted parameters.

Figure 3.1 Typical street canyon.

Figure 3.7 Socialising in a market in Mosul, Iraq 1932.

http://www.loc.gov/ pictures/collection/ matpc/item/

Figure 3.8 Market in Tunisia, 1942. http://www.sigmatur. ru/country/tunis/ photos/9.jpg

Figure 3.9

Deep conversation in

Muharraq cafe. Bahrain, 1950.

Figure

Figure 3.4

Figure 3.5

Figure 3.6

Figure 4.0

Typical neighborhood in Riyadh, Saudi Arabia.

https:// sahelblog.fles. wordpress. com/2010/02/ riyadh.jpeg

4.1

Aerial view of Dubai, UAE.

http://www. listofmages. com/

Contemporary Urban Fabric

Existing Urban Conditions in the Region

“Facilitated by increasing car numbers, and individual transport, the American city freeway has become the icon of modern urban development. The number of cars at a given speed determines width of roads, and pedestrian fows generated by key attractors result in route layout, width and surface design with little notion of spatial qualities generated; spaces are separated according to their usage.”

- Wolf Mangelsdorf, Buro Happold

4.2

Main highway in Riyadh, Saudi Arabia.

http://www. the-saudi.net/ saudi-arabia/ riyadh/75601. jpg

Contemporary urban confguration in the region is based on western urban models. These models are car-centric, and adapted to much more mild conditions. As a result, the city is able to expand over longer distances covered in a much shorter period of time. However, it heavily encourages energy consumption to maintain a controlled indoor thermal environment. Wide streets, highly refective materials, and high albedo amplify radiation in the form of an Urban Heat Island Efect (UHI) making it no longer viable to walk or spend time outdoors for a signifcant amount of the year.

Figure

Figure

Contemporary Tissue Samples

Extracting Physical Parameters of 1Km x 1Km samples from Kuwait City

Figure 4.8

Figure 4.9

Figure 5.0

Figure 5.1

When comparing samples of the same size, it is evident that although the building surface fraction (built:unbuilt) is very similar, the arrangement has a signifcant impact on radiation levels. In the vernacular arrangement most pedestrian pathways were shaded by the surrounding buildings; the opposite occurs in contemporary sample. With the exception of inaccessible spaces caused by setbacks between the buildings, any street is completely exposed to the sun. This is also the direct result of the building typology aiming to maximize the built footprint on a given plot of land.

Figure 5.6

Scale Comparison: Vernacular vs. Contemporary Comparing 100m x 100m samples

Urban Heat Islands

The energy balance of an urban area is made up of several factors. See fgure 5.9. Concrete, asphalt, and other common building materials have a high albedo; they absorb short-wave radiation during the day. This energy is released at night as long wave radiation, which slows down cooling. Unlike vegetation, these materials are impervious and thereby reduce evapotranspiration in urban areas. Cooling, shade, and air quality are greatly reduced with the decrease of vegetation. Shaded or moist surfaces remain close to air temperatures, which occurs more often in rural surroundings. Hence, the diference between heat capacity, thermal conductivity, and surface properties causes a change in the energy balance of the urban area, resulting in higher temperatures in comparison to the surrounding rural areas. (Doick 2013.)

Urban Heat Islands (UHI) are caused primarily by the properties of urban material, the reduction of vegetation, and urban geometry. Signifcant factors that also contribute to the heat intensity are climatic and geographical conditions and population density. The Urban Heat Island Efect (UHI) is ultimately a result of the modifcation of the land surface such that it retains heat. This modifcation in urban settlements occurs by replacing green or permeable ground with highalbedo heat-absorbing buildings, streets and other impermeable surfaces. This disrupts the urban energy balance, see Figure 6.0. With seasonal change, ground cover and solar intensity varies impacting the magnitude of the UHI. Therefore, UHIs are more intense during the summer. Urban geometry can restrain the release of long wave radiation into the atmosphere. The spacing between buildings,

The repartitioning of surface cover means that instead of heating permeable surfaces and releasing latent heat through evapotranspiration, the incoming energy is lost through a heat fux resulting from the mass of the built environment in the form of sensible heat.

percentage of refective surfaces, built density, height, and shape all contribute to how easily long-wave radiation is released into the cooler open sky. Higher built density also blocks wind. The efciency, increased by these factors, of the UHI is called the Urban Canyon Efect. Sky view factor and FAR, therefore, become important values to evaluate the intensity of the UHI.

In addition, land use distribution within a city also impacts UHI. Depending on the population density and the level of activity, surface temperatures within a city vary. Industrial areas, for example, show a signifcantly higher surface temperature than residential areas. Although in cooler climates UHI are seen as a positive efect, as they ameliorate the temperature and prolong plant-growing seasons, they amplify the unbearable heat in desert regions. There is a massive amount of energy spent on cooling, and overall energy consumption. Air pollutants and emissions increase, worsening the greenhouse efect.

Heat Generators in the City Energy Balance Heat fluxes

Type

Long-wave/Infrared Radiation

Short-wave Radiation

Sensible Heat

Anthropogenic Heat

Latent Heat

Source

built environment solar

impervious surfaces

Thermal Storage people vegetation, pervious surfaces impervious surfaces

Figure 5.9 Energy balance in the city.

Figure 6.0

Heat fuxes in the city.

Figure 5.8

The Urban Heat Island (UHI) Efect.

a street comparing pervious and impervious surfaces.

Evapotranspiration

The Impact & Potential of Vegetation and Water bodies Within Urban Context

By altering the amounts of heat energy absorbed, stored, and transferred via the manipulation of surface cover combinations it is possible to efectively modify the urban climate. Adopting evaporative cooling strategies by the use of water and vegetation delivers several mechanisms of cooling simultaneously in a complementary manner (Doick 2013)

Rather than transferring stored energy into sensible heat, it is used to convert water into water vapour through the process of evaporation. Consequently, air temperatures feel lower (Oke 1987) The process is termed evapotranspiration when water is within a plant, on its surface, or in the soil.

“The surface temperature within a green space may be 15–20°C lower than that of the surrounding urban area, giving rise to 2–8°C cooler air temperatures and a cooling efect that extends out in to the surrounding area.’’

(Taha, Akbari and Rosenfeld, 1988; Saito, 1990–91)

Vegetation

The larger the tree, the greater the amount of refected and absorbed solar rays, and therefore the cooler the temperature. See fgure 6.2. The efectiveness and magnitude of cooling resulting from a tree is Dependant on the breadth of its crown, and the density of its leaves. Trees with smaller leaves in a dense arrangement provide more efective cooling, as they maintain lower crown temperatures (Doick 2013).

Large, dense trees yield larger, more intensely shaded areas. Research in Fresno, California has shown that the value of shading is 2.5 times greater than that of cooling due to evapotranspiration. Furthermore, analysis of data collected across the city of Portland, Oregon proved that the temperature under a shading canopy can be 1.7C to 3.3C cooler during the daytime than in areas with no trees (Oliviera et al. 2007).

Hence, the “most important urban characteristic separating warmer and cooler regions was tree canopy cover.’’ (hart and sailor 2007). Thus, informed selection of trees should be based on the following parameters: crown area, leaf area (small vs. large), canopy length, level of water demand, and water resistance. For the case of hot arid regions in the Middle East, appropriate trees are shown on page 55. These trees provide signifcant shade and cooling with low water demand.

Impacts of Vegetation on Climate UK Forestry Commission

Absorbs sound and blocks dust

Provides shade and reduces wind

Evapotranspiration from leaves and soil cools air

pollutants in air

The strategic placement and mindful selection of trees and green infrastructure has the potential to reduce air temperature by 2°C to 8°C.

Figure 6.3

Impacts of vegetation on climate.

Figure

Figure 6.4 Parameters of tree that contribute to maximising cooling.

Oasis Effect

Water and Vegetation

On a urban scale, a study conducted in Petaling, Malaysia confrms that there is a strong correlation between cooling efect intensity and the proximity from the park boundary within the distance of 500 meters. Three parks ranging from 6 Ha to 10 Ha were sampled, and their land cover distribution was compared to their Land Surface Temperature (LST) using GIS and Remote Sensing. Zones were measured at a 50 meter interval. After the 500 meter zone, the efects are disrupted by the presence of other buildings, human activities, and other mature trees. Additionally, the cooling intensity was mainly due to the compactness of the green spaces as opposed to the size of the park (Buyadi et al. 2014) See fgure 6.4.

The cooling efects of the parks were consistent up to 500m. After that, the cooling was disrupted by presence of other buildings, human activities, and other mature trees.

In an urban context, water bodies whether ornamental or not, have a signifcant cooling impact on the surrounding environment. Lower amounts of solar energy is retained due to the refective surface, in addition to a larger portion of energy being directed towards evaporation rather than sensible heat warming the air. This principle is evident in vernacular Arab architecture.

ASTER maps for Beijing, China portray that there was a diference of up to 20C between the downtown area and the suburbs. This correlated with the areas of high built density vs high vegetation/water body concentration (Sun et al 2011). See fgure 6.6.

Studies to quantify the efect of diferent sizes of parks and water bodies on temperature outline the relationship between surface area and change in temperature. Large concentrations of water bodies or planted areas can decrease the ambient temperature of a city, while smaller ones can produce a more local microclimate (Alcoforado et al. 2008).

For water bodies of a surface area of 2 Ha to 5 Ha, cooling within a built context was possible from a radius of 300 meters to 800 meters.

Figure 6.6

ASTER maps for Beijng, China: Land Surface Temperature vs. Ground Cover.

Figure 6.7

Extent of cooling for vegetation and water of a certain size within an urban context.

Figure 6.4

Three parks of 6-10 Ha tested in Malaysia for their cooling impact. Buyadi, Misni, Naim 2014

Thermal Comfort

Relative Comfort Zones

Thermal comfort is a relative and subjective condition of satisfaction with the thermal environment (Ashrae 55). The six primary factors that afect human thermal comfort that fall under two categories: physiological and environmental. The former are unique to the individual’s metabolic rate and clothing; faster metabolism and heavier clothing mean a higher rate of transpiration. There are four environmental conditions: air temperature, air velocity, relative humidity, and mean radiant temperature. See Figure 7.0.

Although air temperature is the most common indicator and most infuential factor, it is inaccurate to consider it without combining it with other environmental parameters. For example, the felt temperature can vary up to 20°C due to high wind velocity. (Nasir 2013)

There are several indices and human energy balance models that attempt to quantify perceived temperature based on the comfort equation developed by P.O. Fanger in 1972. The basic principle builds upon the correlation between skin temperature, activity level, and evaporation rate; more active individuals were comfortable with low skin temperatures and high evaporation rates (Hygge 1990). Hence, low skin temperature is based on two factors: clothing and metabolism, while evaporation rates are driven by humidity, air temperature, velocity, and radiation. This relationship is represented by the Predicted Mean Vote (PMV). This allows for a relative scale to predict the level of discomfort. Following this, the Klima-Michel Model was developed by Jendritzky in 1990 (Matzarakis 1997) which references comfort standards in relation to Michael, a 35-year old Western male. Indices such as the Heat Index (Steadman Model 1994) and Physiologically Equivalent Temperature (PET, Hoppe 1999) were then derived by diferentiating the emphasis on the six primary parameters. These have been compared in the methods chapter.

Though the results of these indices vary slightly, choosing an index will greatly depend on the local climatic conditions. For example, in cold climates Wind Chill rates human discomfort by emphasizing velocity. In hotter climates, however, the Physiologically Equivalent Temperature (PET) has been used in scientifc study (Doick 2013).

Because comfort levels have been in relation to Western ideals, an adjustment is necessary to adapt to Middle Eastern perceptions of temperature and comfort. Major diferences include clothing material and cover, in addition of what conditions of a “pleasant day’.

Thermal Comfort & Perception of Space

Research on bioclimatic conditions and the perception of space verifes that despite the physical appeal of a space, its perception is heavily altered if it fails to fall within comfort thresholds. In a study conducted in Malaysia, three gardens were compared and surveyed in terms of comfort and perception. Although the roof garden rated higher in terms of design, it received a high amount of solar radiation and thus remained empty. On the other hand, the court garden was rated more appealing because wind and radiation were within comfort range, and was ameliorated by the presence of water fountains and trees. In this study, low radiation and cross ventilation deemed the most infuential factors on thermal comfort (Taib et al. 2010).

Another study conducted in Lisbon aimed to assess bioclimatic comfort in outdoor space and to correlate actual climatic conditions with what people perceived. This study concludes that people were generally more sensitive to wind than any other parameter, and overestimated its condition. Furthermore, the optimal human performance ranges from 27°C to 32°C in outdoor conditions. (Alcoforado 2007)

Thermal Comfort Scales

Figure 7.0

Chart outlining the necessary levels of wind velocity, moisture, and radiation to achieve thermal comfort.

Based on Olgayay Bioclimatic Chart.

Figure

Figure 6.9

Comparison between thermal stress levels in temperate vs. desert regions.

Based on the Klima-Michel Model. W

Contemporary Public Space in the Region

Mapping comfort zones at diferent points in a park in Cairo, Egypt.

Due to the concentration of vegetation and water bodies that make up most urban parks, they ameliorate the urban microclimate and an individual’s thermal perception. Studies referenced in this paper illustrate that shade and evapotranspiration has a cooling impact from 1 to 4.7°C.This impacts the use of outdoor spaces, especially in hot and arid regions. This study investigates the climatic efects on human comfort of an urban park in the midst of Cairo, Egypt. Nine diferent zones were chosen based on thermal environmental parameters: air temperature, solar radiation, relative humidity, and wind speed. The most relevant zones to this research were: spine, entrance, fountain, and cascade. See Figure 7.2.

Data was recorded during June (summer) and December (winter), in addition to a subjective survey based on the ASHRAE 55 seven-point Thermal Sensation Vote (TSV). Users were asked to rate their thermal comfort at this location from -3 (winter) to +3 (summer); where the ideal comfort zone was -1 (winter) to +1 (summer). This was graphed against the Physiologically Equivalent Temperature (PET), which was calculated using the RayMan model. The model takes into account the time of day and year, air temperature, air humidity, degree of cloud cover, and the albedo of the adjacent surfaces.

Sky view factor (SVF) and shade afect behavioral performances, both which are greatly afected by geometry and orientation. This is mainly because SVF and orientation of streets afects the absorption and emission of the incoming solar and the outgoing long wave radiation. In addition, this study discusses the “cooling capacity for some orientations and levels of urban density due to the compact form and green

Comfort surveys for Predicted Mean Vote (PMV) suggest that parks are a failed model in the region, due to high radiation and lack of moisture. Highest comfort levels were near water.

cool islands and fow of wind through main street canyons.”

(Hassaan et al. 2011)

The diferences in the PET indices result due to diferent sky view factors (SVF), the presence of moving water, and wind speed. These factors also afected the human comfort levels, and thus, should be taken into consideration when designing landscapes in hot, arid regions. It also further emphasizes that the notion of a park, a foreign concept to the region, does not work and does not encourage the use of outdoor public space.

This study concludes that the presence of water is essential to provide a comfortable microclimate, and that parks are a failed model in the region. Furthermore, trees should be arranged in clusters or groups to provide shading rather than lined where their function becomes mostly aesthetic. Shaded seated areas should also be placed. (Hassaan et al. 2011)

Analytical Techniques for Assessing Thermal Comfort

When evaluating thermal comfort, the meteorological method involves an analysis of air velocity, turbulence, thermal variations, and pollution concentration. This data is collected at diferent mobile stations across the city. This method, albeit easy to carry out, is limited and time consuming because only a certain number of parameters can be measured simultaneously especially when a 3D spatial distribution of the relevant factors is not always possible. This data, in combination with adaptive thermal comfort predictions, can then be used to locate urban heat islands within a city by studying the points of increased ambient temperatures.

Thermal remote sensing and GIS have also been used to locate UHIs (Oke 2003). This method provides information on surface temperature, surface radiation, and thermodynamic properties. However, due to atmospheric interactions, it is not possible to obtain steady images of the urban surface at all times. In addition, it is very expensive because images are generated using satellites and aircrafts.

A more accessible method is to use simulation software where a replica of a portion of the urban area is constructed. This model is evaluated using energy balance models and computational fuid dynamics (CFD). See Methods.

Recorded Sky View Factor: 0.78

Due to the high sky view factor, people were not comfortable in this location of the park. The surrounding materials also had a high refectivity, which further amplifed the heat.

Recorded Sky View Factor: 0.69

The main spine is approximately 7 meters wide. Trees lined along the spine only defned the path, rather than shade the walkway itself. Pedestrians walk through an exposed long path that stretches down the middle of the park, with only seating along it. Though it has a low SVF, it is one of the most uncomfortable locations.

Recorded Sky View Factor: 0.78

The presence of water made little diference to this area, because of the lack of concentration of surface area. In order to have a cooling efect, water must be present in the form of pools, or exposed surface area moving at a regular pace. In this case, water splashes at an instant providing more of an aesthetic function.

http://www. gardenvisit.com/ uploads/image/

Recorded Sky View Factor: 0.87

Though the radiation during the hottest day of the year is high, the recorded comfort level at this location was ideal. Due to the presence of moving water, people were able to feel comfortable and endure the heat even on an extremely hot day.

http://media-cdn. tripadvisor.com/ media/photos/02/2d/5a/22/ fountain.jpg

Figure 7.1

Aerial view of AlAzhar Park, Cairo, Egypt.

Figure 7.4 Fountain

Figure 7.5

Moving Water

http://media-cdn. tripadvisor.com/ media/photo-

Outdoor spaces in hot , arid regions CONCERNS

Building arrangement high radiation, low canyon ratio

Building material hot air, high albedo

Aridity poor soil quality, low vegetation

Water Stress low availibility, high consumption

Precedents

Canyon Ratio > 1.5

Cool Walls

Regional Vegetation

Bioremediation: constructed wetlands

Potential for new morphology of public space

Masdar Institute

Sony Bioskin

Wadi Hanifa

Precedents

Bioskin - Nikken Sekkei, Tokyo

The installation of this system on multiple buildings has the potential to lower the city temperature collectively, as it can cool the surrounding microclimate by 2° C to 3°C. The system decreases the building surface temperature by 12°C, thus making a 3% diference in energy expenditure.

BioSkin is an evaporative cooling system installed on building facades designed to reduce energy usage by 3%. (Sekkei 2011)

The system is made up of ceramic pipes with an aluminum core of a diameter of 110mm by 70mm that are flled with water. Rainwater is collected from the rooftop, and drained to a subsurface storage tank. It is then fltered and sterilized, and pumped up and circulated through the pipes. The water evaporates through the porous ceramic, cooling the surrounding air. The excess water is then drained down to soil, which reimburses moisture within the ground and reduces the load on the sewage infrastructure. See Figure 7.9.

Figure 7.9

Water cycle through the building used for evaporative cooling.

Figure

Figure

http://www.

Masdar Institute, UAE

Masdar Institute is part of Masdar City, a prototypical and sustainable city in Abu Dhabi developed as a test base for environmental technologies; it aims to be powered entirely by renewable solar energy. The design draws heavily on passive and active environmental strategies such as shaded streets, water bodies and solar panels. Buildings are typically four storeys high, and streets are 5 meters wide. Upper foors have few fenestrations, while the ground foors are more porous with 45% glazed area.

Openings are designed to provide maximum natural ventilation, with walls that surpass the insulation standards of the ASHRAE by over two times. They are shaded by horizontal and vertical fns. There are frequent water fountains in public courtyards and walkways. Passages usually maintain a canyon ratio of 3 on average.

The building operates on energy produced by a 10 megawatt solar feld, and uses only 40% of the energy provided. This is partially due to the treated outdoor material fnishing. The remaining 60% is then fed back to supply Abu Dhabi. Three-fourths of the hot water used is heated by the sun. (DesignBoom, 2010)

There are frequent water fountains in public courtyards and walkways. Passages usually maintain a canyon ratio of 3 on average. The building operates on energy produced by a 10 megawatt solar feld, and uses only 40% of the energy provided.

Precedents

Wadi Hanifa, Saudi Arabia

Wadi Hanifa is a 120 km long valley in the middle of the Najd Plateau in Riyadh, with a natural water drainage course which covers an area of over 4,000 square kilometers. The valley has undergone a bioremediation and rehabilitation project engineered by Buro Happold, and won the Aga Khan Award in 2010. See Figure 8.4.

The wadi is subject to seasonal fooding, and with water fowing from the city sewage combined with the rising groundwater needed signifcant treatment and restoration. Rather than depending heavily on desalination and using traditional techniques, the water was remediated thereby providing water for irrigation. The areas around its banks were landscaped such that they encouraged its use as a public space, and reinforced activity to residents living around the area.

The project has successfully converted a wastewater management facility into a tourist attraction, and reimbursed balance into the local ecosystem including vegetation and birds. Additionally, since it is the city’s most prominent feature amidst a dry area, it also helped form a more mild microclimate.

-Buro Happold, 2010

The project involved the reclamation of a 3.4 mile long vehicular street and its replacement with a watercourse and river bed in Korea. With the increase in open public space, bridges were constructed at intervals throughout the promenade to improve and encourage pedestrian mobility across this landscaped corridor.

The introduction of this project has shown to reduce temperatures by 3.3°C to 5.9°C in comparison to a parallel road 4-7 blocks away. REF. The cooling efect of the stream, reduction of vehicular movement, and increase in vegetation in turn also led to wind speed increasing from 2.2 to 7.8%. Air pollution was also reduced by 35%, which meant residents around the area are half as likely to sufer from respiratory disease than in other parts of the same city.

Figure 8.6

River Restoration.

http://static. panoramio. com/photos/ large/12155043.jpg

The introduction of this project has shown to reduce temperatures by 3.3°C to 5.9°C in comparison to a parallel road 4-7 blocks away. The cooling efect of the stream has also led to the reduction of vehicular movement, and increase in vegetation.

Figure 8.7

Street reclamation activates public space

http://3. bp.blogspot. com/_16i_ C8BxwU8/ TJhZUxztY8I/ AAAAAAAAAkQ/ ODg8ltjP__w/ s1600/IMG_1989.

Figure 8.4

The Wadi Rehabiliation activates public space around it.

www. burohappold.

Figure 8.5

People spend time beneath the trees.

Cheongyecheon Restoration Project, Korea

Figure 8.8 River creates microclimate up to 6C less

http://webarchive. nationalarchives. gov.uk/

Constructed Wetlands

Constructed wetlands are secondary treatment systems which operate on the basis of running grey, black, or brown water through a planted flter bed. These systems do not require chemicals, energy or high-tech infrastructure (Tiley 2014).

In addition, they work well when combined with irrigation systems. Wetlands are typically 70 cm deep, with water fowing 10-15 centimeters below the surface. There are three main types of constructed wetlands: free-water surface fow, horizontal subsurface fow, and vertical subsurface fow.

Constructed wetlands require minimal or no maintenance, and can be constructed with available materials such as gravel and sand. They also help in clearing pathogens from water, and increasing the vegetation cover within a city.

Free water surface fow systems provide a natural habitat for animals. Simultaneously, however, they also attract mosquitoes and bugs which can be disruptive in an urban context. Vertical and horizontal fow systems do not face this problem.

Vertical fow systems require less space, enabling them to work well within compact urban settings where space is scarce. Horizontal subsurface fow systems are simple to construct, and is suitable for hot climates.

For the purpose of this research, the horizontal subsurface fow will be adopted. In hot climates, wider canals are necessary in order to maximise evaporative cooling without attracting insects.

Local halophytes in the region include sea rush,

common reed, sea lavender and the desert bunchgrass. They tolerate aridity and full sun. They can help improve soil quality and flter the water. Size ranges from just below 0.5 m to 3m (Tiley 2014).

Types of Halophytes Suitable for Hot, Arid Regions

Horizontal Subsurface Flow

Advantages and Disadvantages of Wetland Systems

Advantages

Free Water Surface Flow

Subsurface Flow

System Type Disadvantages attracts mosquitoes, requires wide land area requires supervision

aesthetically pleasing, moderate pathogen removal, no electrical energy required

low operation/maintenance, does not attract mosquitoes, odour free, high pathogen reduction

Figure 9.1

Horizontal subsurface fow section.

Figure 9.2

Comparison between water surface fow and subsurface fow.

Figure 9.3

Shanghai Houton Park wetlands.

http://www.

Kuwait City, Kuwait

A Test Case for Urban Cool Islands

Kuwait is situated on the northernmost part of the Arabian Gulf. Its climate is extremely dry with temperatures soaring above 45°C in the summer. The prominent wind comes from the NorthwestSouthEast axis. Although it is next to the sea, the breeze is hindered due to the high salinity levels.

Prior to the discovery of oil in Kuwait in 1952, the existing urban tissue was driven by the local climatic conditions and refected cultural values. This resulted in a very tightly knit fabric where streets were narrow, intensely shaded by the walls surrounding them. In addition, a clear spatial hierarchy of gradual transition from private to public meant that there was a strong sense of orientation. Shared spaces were an essential part of this logic, from the courtyard in the house to the very public clearing near the market street, making them points of reference. Programmatically, similar functions were clustered to form specialized streets and districts. Relatives and close families would usually resided in the same street (Aljassar 2009).

Despite the small spaces, however, a clear hierarchy can be observed on diferent scales. This not only maintained navigation within the city, but followed a strong social structure. Within the household, rooms were arranged surrounding a courtyard, which in relation the activities within the house, was considered to be a semi-private space. Bedrooms were located at the very back of the house. The Diwaniya, the room where men entertained other male guests, was located at the very front of the house along with an outdoor seating. See Figure.

Residents of one street often meant that they were related or very close friends. This resulted in small spaces in between the houses for children to play in, and women to socialise during the day. These spaces physically manifested as a result of recessions within the house prototype. See Figure.

These private streets then connected to a secondary network, which then led to a primary route and eventually a large clearing or square. Surrounding these squares public functions such as markets and mosques were located. This meant that the square was not only a transitional space, but also where people met most frequently en route to the most popular activities. Based on the principles of graph theory, the square has the highest betweenness value within a network. See Figure 4.

https:// c2.staticfickr.

Although the vernacular model refected the regional values and worked to ameliorate climatic conditions, it failed to accommodate the rapid growth that came with industrialization. It was not only a limitation of the sudden surge in the increase of the number of people, but the change in the mode of transport - from foot to caras well.

The implementation of a new master plan in 1952 based on the Garden City inverted the vernacular organisation. The original city bounds became the city business center, and residents were given dispersed housing outside it. The introverted courtyard model was replaced by an extroverted villa, and narrow streets were replaced by wide ones to accommodate cars. Neighborhoods followed a “self-sufcient” model, such that at its center was a supermarket, clinic, school, and mosque. A “green belt” surrounded the city center. Thus, much of the shading, and thereby the notion of public space disappeared. Due to the heat, parks are not used most of the time. See Design Proposal.

Unlike the vernacular network, contemporary urban fabric follows a more direct-path approach. The transition from private to public space is no longer present; public zones begin at the parking spots directly preceding the house. Public areas and parks are isolated, and become a destination rather than a connector. Programmatically, they are not surrounded by attractive functions. Furthermore, they are no longer shaded which, along with the previous factors, leads them to be one of the most unvisited places in the city.

As a consequence, the contemporary city becomes less sociable, connected, and much less thermally comfortable. It is no surprise that the frst spaces of the city to sufer are the public spaces that were once essential to the social infrastructure and its health.

http://www3. hilton.com/ resources/media/ hi/KWIHIHI/en_ US/img/shared/ full_page_image_ gallery/main/HL_

Figure 9.5 Kuwait skyline.

Figure 9.6

Contemporary Kuwait aerial view.

Figure 9.4

Aerial view of Kuwait prior to the application of Garden City

Figure 9.8 Outdoor seating was located in front of every house.

https://www. magnumphotos. com/

Figure 9.9

Figure

Existing Public Spaces in Kuwait

The municipality park is located in the city center, beside the municipal complex. It is surrounded by commercial and ofce buildings. However, it is isolated by vehicular roads and parking lots on all sides. This makes it merely a place to cross from one parking to another.

It does not connect to any other space or function, and due to the lack of shading is exposed to a large amount of radiation.

The Safat Square is a landmark square in downtown Kuwait City. It holds historical and political signifcance, yet is only used as a transitional space. It can be accessed on foot from the market directly adjacent. It is sunken and contains small shops at the bottom under a gallery.

It also lies on one of the main roads. Yet because it has no seating, is not shaded, and is exposed to high radiation it is often unoccupied.

The beachfront is the most prominent promenade in Kuwait. It is lined with low bushes and dispersed trees. The beachfront is lined with restaurants, cafes, hotels, and commercial centers.

It is further connected by a pedestrian walkway, which is occupied mostly after sunset. The space, however, is directly fanked by parking lots and is separated from the rest of the city by the Gulf Road.

AlSafat Square

This tree provides wide areas of shade, and is known as the local gum tree. In addition , it stabilizes the soil and prevents erosion, and thus can help during dust storms.

The Neem tree is an evergreen tree with a canopy typically ranging from 15-20 meters. Its small, dense leaves make it ideal for transpiration as well as shading. The tree also has medicinal uses known within the region.

The Egyptian Mimosa has an extremely dense spherical crown, and is extremely durable. Its leaves are small and dense.

The Date Palm is durable, tall, and provides a variety of dates essential to the regional diet. Date palms tend to be planted in groups, and provide signifcant shade as their crowns come close together.

The almond tree is very tall, and though its crown is not wide it spreads as the tree matures.

Acacia Tree Arabic Gum Tree

Azadirachta Indica Neem Tree

Acacia Niloteca Egyptian Mimosa

Phoenix Dactilyfera L. Date Palm

Terminalia Catappa Malabar Almond

Research Question

Given the harsh conditions present in contemporary cities in hot, arid climates outdoor comfort has been greatly compromised. While vernacular urban models have succeeded in providing dispersed, shaded communal spaces, they fail to integrate a vehicular transportation system within the city fabric. Conversely, contemporary urban planning is based on western logic adapted for a much more mild climate where buildings are made of refective material arranged around wider more open streets and spaces. As a consequence, these cities sufer from an extreme Urban Heat Island Efect resulting in felt temperatures soaring above the 45C air temperature. Research has proved that the introduction of vegetation and water bodies can reverse this efect through evaporative cooling and shading.

The aim of this research is to explore the potential of informed and careful organization of vegetation and water on comfort in outdoor spaces. This involves an alteration in built arrangement and morphology, and use of several evaporative cooling strategies: cool walls, constructed wetlands, and shade trees. The collective efect of these elements on felt temperature is termed an Urban Cool Island.

The thesis attempts to answer the following questions:

1. In which format can these cool islands exist in an urban context, and in what arrangement?

2. In which proportion should these elements exist in order to maximize cooling?

3. What is the radius of cooling provided by these diferent combinations? Is there a potential to cool beyond the immediate area?

4. Can Urban Cool Islands provide an opportunity to reintroduce outdoor public space in the region?

Elements of an Urban Cool Island

1. Which sequence and arrangement achieves maximum cooling?

2. Is it possible to create a differentiation in outdoor space as a result of cooling?

Domain References

1. Corsi, Buf. “The Desert Biome.” University of California Museum of Paleontology. 1 Jan. 2004. Web. 1 Jan. 2015.

2. “Characteristics of Arid Climates | eHow.” eHow. N.p., n.d. Web. 24 Jan. 2015.

3. “Arid and Semi-Arid Lands: Characteristics and Importance.” IISD. Web. 24 Jan. 2015.

4. “BIL 160 - Lecture 19.” N.p., n.d. Web. 8

5. Peell, M. C., B. L. Finlayson, and T. A. McMahon. “Updated world map of the Köppen-Geiger climate classi ication.” Hydrol. Earth Syst. Sci 11 (2007): 1633-1644.

6. “Global Aridity and PET Database CGIAR-CSI.” N.p., n.d. Web. 8 Feb. 2015.

7. Zomer RJ, Trabucco A, Bossio DA, van Straaten O, Verchot LV, 2008. Climate Change Mitigation: A Spatial Analysis of Global Land Suitability for Clean Development Mechanism Aforestation and Reforestation. Agric. Ecosystems and Envir. 126: 67-80.

8. Pang, Garwood. “China and Middle East Middle East & North Africa.” Virtual Water, Univeristy of British Columbia. Print.

9. Akber, A. Water Securities in Kuwait: Aspirations and Realities. Kuwait: KISR, 2014. Web.

10. Doick, Kieron, and Tony Hutchings. “Air Temperature Regulation by Urban Trees and Green Infrastructure.” UK Forestry Commission. Forestry Commission Publications, 1 Feb. 2013. Web. 1 Dec. 2015.

11. Wong, Eva, and EPAOAP. “Reducing Urban Heat Islands: Compendium of Strategies Cool Pavements.” (2005): 37. Web.

12. Buyadi, Afzan, Alamah Misni, and Wan Mohd Naim. Quantifying Green Space Cooling Efects on the Urban Microclimate Using Remote Sensing and GIS Techniques. Kuala Lumpur: FIG CONGRESS 2014, 2014. Web.

13. Alcoforado, Maria-João, Henrique Andrade, António Lopes, and João Vasconcelos. Application of Climatic Guidelines to Urban Planning The Example of Lisbon (Portugal). Lisbon: U of Lisbon, 2007. Print.

14. Taib, Nooriati, Aldrin Abdullah, and Sharifah Fadzil. An Assessment of Thermal Comfort and Users’ Perceptions of Landscape Gardens in High Rise Ofce Building. Vol. 3. Penang: Universiti Sains Malaysia, 2010. Web.

15. AE, Enander, and Hygge S. Thermal Stress and Human Performance. Karlstad: National Defence Research Establishment, Scandinavian Journal of Work, 1990. Web.

16. Nasir, Adawiya, Sabarinah Ahmad, and Azni Zain. Perceived and Adaptive Thermal Comfort at an Outdoor Shaded Recreational Area in Malaysia. Geneva: TransTech Publications, 2013. Print.

17. Matzarakis, Andreas, and H. Mayer. “Heat Stress in Greece.” International Journal of Biometeorology 41.1 (1997). Springer-Verlag. Web.

19. Erell, Evyatar, David Pearlmutter, and Terry Williamson. Urban Microclimate. Vol. 1. London: Earthscan, 2011. Print.

20. Oke, Timothy R., and I.D. Stewart. “Datasheet for Local Climate Zones.” American Metereological Society (2012). Print.

21. Hassaan, Ayman, and Ahmed Mahmoud. “Analysis of the Microclimatic and Human Comfort Conditions in an Urban Park in Hot and Arid Regions.” Building and Environment 46.12 (2011). Print.

22. Tilley, E. “Horizontal Subsurface Flow.” Sustainable Sanitation and Water Management. Swiss Federal Institute of Aquatic Science and Technology, 1 Jan. 2014. Web. <http://www.sswm.info/ category/implementation-tools/wastewater-treatment/hardware/semi-centralised-wastewater-treatments/h>.

23. Sun, Runhao, and Liding Chen. “How Can Urban Water Bodies Be Designed for Climate Adaptation?” ElSevier (2011). Print.

24. AlJassar, Mohammed. Constancy and Change in Contemporary Kuwait City The Socio-Cultural Dimensions of the Kuwaiti Courtyard and Diwayniyya. Milwaukee: U of Wisconson ProQuest LLC, 2009. Print.

25. Foster + Partners: Masdar Institute Campus - Designboom | Architecture & Design Magazine.” 2015. Designboom | Architecture & Design Magazine. Accessed January http://www.designboom. com/architecture/foster-partners-masdar-institute-campus/. “reStreets.” N.p., n.d. Web. 28 Jan. 2015.

26. Oliveira, Sandra, and Henrique Andrade. “An Initial Assessment of the Bioclimatic Comfort in an Outdoor Public Space in Lisbon.” International journal of biometeorology 52.1 (2007): 69–84. Print.

27.Latini, G, R C Grifoni, and S Tascini. “Thermal Comfort and Microclimates in Open Spaces.”

Methods

Computational Tools

Comparing Computational Tools, Indices, and Mathematical Models

After comparing mathematical equations for calculating indices, available software, and what can be incorporated into the grasshopper environment a selection was made. However, the wokfow still involves three diferent platforms: the grasshopper environment, CFD, and rayman index calculator. With Grasshopper, a complete loop can be developed using the Ladybug plug-in in order to generate results that take radiation into consideration. Wind simulation cannot be taken into consideration in a continuous loop, but can be used as an evaluation and to extract principles that can be implied through rules in Grasshopper. After all of the above, the resulting radiation, wind velocity, and data must be manually input in RayMan to generate a felt temperature index PET. Though this fow is more time consuming than having everything in one platform, it takes more factors into consideration, making the numerical results more accurate.

Computational Tools Comparison Limitations and Advantages

Ecotect Radiation Analysis Plug-in

Simulation CFD

Heat Index

Physiologically Equivalent Temperature (PET)

Radiation Analysis Software

Fluid Dynamics Software

Index

3D mesh, ground surface, epw weather file

3D mesh, epw weather file, material properties Temperature, wind velocity, 3d model (solid)

Temperature, Relative humidity

Temperature, wind velocity, relative humidity, sky view factor, human metabolic rate

Temperature, wind velocity, relative humidity, sky view factor, human metabolic rate, human vote

Temperature, wind velocity, relative humidity, sky view factor (fisheye photo/free drawn), human metabolic rate, material properties, vegetation type

visual radiation projection on 3d model, shadow hours, sky view diagram and value

Weather data, visual radiation projection on 3d model, shadows

visual diagram of wind velocity and pattern due to 3d arrangement, air temperature, air pressure

Heat Index/WindChill Factor

Felt/physiologically equivalent temperature

or comfort level at that temperature

1 minute

TSV, Radiation including materials,

does not consider materials, does not consider heat exchange

not within grasshopper environment, takes very long for a small mesh setting for precision

not within grasshopper, based on a portion of urban tissue, is based on a static condition (one instant of time)

does not consider human metabolic rate, no visual diagram

Assumes human metabolic rate (general), is part of a more complex MEMI equation, no visual diagram

based on subjective vote, is part of a more complex MEMI equation, no visual diagram

does not take ready 3d models, no visual output, sky view must be drawn by hand in software/photos

Computational Work Flow

INPUT

COMPUTATIONAL TOOLS OUTPUT

Hottest day conditions (14th August)

Temperature 45°c

Wind velocity

7 m/s

Humidity

6%

Existing site conditions (3D model)

Fluid dynamics (Autodesk Simulation CFD)

Solar radiation analysis (GH Ladybug)

Thermal comfort analysis (RayMan)

Wind speed (m/s)

Air temperature (°C)

Radiation (W/m2)

Physiologically equivalent temperature PET (°C)

Comfortable conditions (21st April) compare

Temperature

33°c

Wind velocity

4 m/s

Humidity

40%

Selected Computational Tools

Autodesk Simulation CFD (Computational Fluid Dynamics)

Although Simulation CFD is originally a mechanical engineering tool, it can provide insight of outdoor environments surrounding buildings. In relation to other methods, it is quick and fairly accurate. Due to the increase in density of the urban environment, there is a rise in energy demand. This causes trapped radiant heat and obstructed winds, and hence, great outdoor discomfort (Setaih et al., 2014). Thus, a modifcation to local wind patterns, humidity, and ambient temperature occurs causing urban micro-climates to face signifcant changes in atmospheric characteristics (Setaih et al. 2014).

Simulation CFD takes into consideration energy and heat exchanges between the surfaces of buildings, pavements and streets. It is also possible to assess a range of issues dealing with air speed and movement, wind comfort and air temperature. Thus, it can analyze complex environmental phenomena. This allows for the prediction of important micro-climatic parameters through the understanding of fuid fow around buildings, and hence prevention of turbulence, pollution concentration and stale air.

The software requires a 3D model converted to a .sat format fle. Elements in the 3D model must be comparable in scale; CFD will omit small geometry if the surrounding context is much larger. The model should be bound by a cube, or an assumed volume of space. This cube should be 2-5 times the length of the highest building in order to ensure stable incident fow. The model is then assigned materials, surface temperatures and boundary conditions. See fgure x. Before the solver is run, the model is converted into a mesh. Larger mesh divisions means more rapid calculation, while smaller ones give a higher resolution result. Once the solver begins, velocity and temperature felds are separated. Air velocity and heat exchange are calculated frst, until it converges into a solution. Based on that solution, air temperature is then calculated. Accurate results need 300-700 iterations. This requires powerful computers, as it is very time consuming.

Simulation CFD exports still and dynamic images. With the latter results are both visual and numerical; it is possible to extract the exact velocity at a certain point. However, the value is a compilation of several hundred iterations and represent a single instance. In addition, the change in humidity cannot be extracted, only the change in air temperature.

RayMan

RayMan is a model developed by the University of Freiburg to calculate short and long wave radiation fuxes on the human body. It has been used by many of the latest studies conducted for bioclimatic assessment. The model takes into account complex urban structures and heat exchange as well as location and climatic conditions. It is therefore very useful for applications in urban and street design, and has proven very accurate when compared to on-site results. Possible outputs are the values for Mean Radiant Temperature, Predicted Mean Vote (PMV), Physiologically Equivalent Temperature (PET), and Standard Efective Temperature (SET*).

Rhinoceros 3D

McNeel & Associates

Rhinoceros 3D, or Rhino, is a three-dimensional modeling software based on the NURBS mathematical model. It can produce mathematically precise curves and free-form surfaces. It is a computer aided (CAD) design tool, used in architecture, industrial design, and product design. It is compatible with scripting and visualization tools, such as Grasshopper and V-ray. It currently runs mainly on Windows, although a beta version is available for Macintosh.

Parametric Modeling & Scripting Software

Grasshopper 3D

McNeel & Associates

Grasshopper is a visual scripting plug-in for Rhino3D, mainly used for parametric modeling. Elements from the Rhino environment can be imported and then exported in the form of mesh, brep, or polysurfaces. Several plug-ins are available to evaluate the outputs within the Grasshopper environment. In architecture, these are mainly for environmental, structural, material, or mathematical purposes. Plug-ins used in this research are Ladybug + Honeybee, Octopus, and Python.

GhPython enables the Python programming language to be incorporated within the Grasshopper environment. Rhino commands can be imported as rhinoscriptsyntax in addition to Python and .Net commands. GhPython is especially useful when sorting data lists and trees based on if-then principles.

Ladybug + HoneyBee

LadyBug is a plug-in for Grasshopper that provides radiation and shade analysis by importing standard EnergyPlus Weather fles (.EPW). It provides a variety of 3D interactive graphics like a radiation mesh which aids in understanding the 3D model physical arrangement. This allows for more conscious decisions in the initial stages of design.

Honeybee grants access to softwares like Dayism, EnergyPlus, Radiance, and OpenStudio for daylighting and building energy simulation.

Octopus is a Grasshopper plug-in that implements evolutionary principles in parametric design and problem solving. The plug-in provides design options and patterns generated during the search for many options simultaneously. The result is a wide range of solutions sub-optimized for several ftness criteria. It is based on SPEA-2 and HypE and the grasshopper Galapagos interface. It requires a 3D mesh as an input from a grasshopper model, and a set of changing parameters (genes) and at least two ftness criteria to measure the results against. It is possible to direct the solution based on a preferred physical arrangement (phenotype) or numerical makeup (genotype). Moreover, the search space can be defned by the population size (i.e. number of options produced at each iteration), number of generations (iterations) and the percentage of ft or unft solutions carried forward. The output is a 3D polysurface and a set of charts with the evaluation criteria values.

Octopus

GhPython

Figure 1.1

Example of GA pseudocode.

http://fle.scirp. org/Html/7-

Algorithms

Genetic Algorithms

A genetic algorithm is a problem-solving search algorithm based on the process of natural selection. It belongs to a wider category of Evolutionary Algorithms, which aims to generate solutions optimal for a set of problems. The techniques used to generate variation are based on genetic mutation, insertion, deletion, and crossover. Each variant, or individual within a “population” of possible solutions is then evaluated against a pre-set ftness criteria which determines “ft” or “unft” solutions. Because these parameters are highly dependent on the design objective, a solution is said to be sub-optimised for a particular purpose. There are also other forms of fltering results, such as elitism, which guarantees that the ftness quality of a population is constant from generation to generation.

Initialise population

Figure 1.2

Example of CA pseudocode.

http://upload. wikimedia. orgLampFlow chart. svg/2000px

Selection

Computational Algorithms

Computational Algorithms comprise of precisely defned set of operations to be carried out on a set of data, for a fnite number of iterations. The result is a another set of data. It does not “learn” or use a search space in order to fnd a solution; it is merely a tool to execute commands in mass. This process is very deterministic, and is used largely in data management.

Methods References

1 Setaih, Khalid, Mohammed Mohammed, Steven Dudek, and Tim Townshend. “CFD MODELING AS A TOOL FOR ASSESSING OUTDOOR THERMAL COMFORT CONDITIONS IN URBAN SETTINGS IN HOT ARID CLIMATES.” Journal of Information Technology in Construction 19 (2014). Print.

2. Davidson, Scott. “Plugins.” Grasshopper3D. 1 Jan. 2011. Web. <http://www.grasshopper3d.com/group/ ladybug>.

3. Rutten, David. “Plugins.” Food4Rhino. McNeel Europe, Jan. 2015. Web. <http://www.food4rhino. com/?ufh>.

Design Development

Initial Experiments

Experiment 1

Testing the impact of 3-Ha water body arrangements & geometry on air temperature.

The aim of this experiment is to determine the extent of cooling due to water body arrangement and geometry.

Diferent arrangements of a 3 Ha water body with a depth of 0.3 m were tested in CFD.

The incoming wind was set at 2 m/s coming from the top, perpendicular to the water bodies. The air was set at a humidity of 6% and a temperature of 45°C, which were extracted from the hottest day conditions in Kuwait. Water temperature was assumed to be at 30°C, since it would have to be cooler than the air temperature in order to cool it.

Velocity 2 m/s, perpendicular water surface area: 3 Ha

Air temperature: 45°C

Humidity: 6%

water depth: 0.3 m water temperature: 30°C

Wind passing over a longer distance of water body is more efective in cooling a longer distance. For example, Case 4 the air passes over a water body of 250 m and cools 500 m ahead (twice as much given that it is at least 20 meters wide). This is given that the water body is perpendicular to the wind direction.

Wind speed must decrease prior to passing over a water body to cool the surroundings.

For a water body of 3 Ha, arranging it in smaller 1-Ha bodies provides more efcient cooling. Case 5 and Case 6 show that arranging the water bodies in a consecutive manner cools up to 250 m more.

Since this experiment was set independent of any urban context, these values are ideal. A main assumption is also that the water temperature is at 30°C, which would only happen if the water body is in shade.

Experiment 2

Testing the impact of wetlands within urban context.

BODY ARRANGEMENT

COOLING PATTERN

The aim of this experiment is to defne the scale and pattern at which cooling occurs in an urban context by insertion of diferent arrangements of a 3 hectare water body.

A 500 m x 500 m patch of a business district and a neighbourhood were modeled. A 3-hectare water body was then placed around the edge, horizontally, and vertically in the business district. In the neighborhood, the 3 hectares were dispersed.

For radiation analysis the site location was set to be in Kuwait City on the hottest day, on August 14 from sunrise to sunset.

In CFD, the incoming wind was set at 7 m/s coming from the NorthWest-SouthEast direction at a humidity of 6% and a temperature of 45°C.

Velocity 7 m/s, NWSE

Radiation: August 14 (hottest day)

wetland surface area: 3 Ha

Air temperature: 45°C

Humidity: 6% 1. Water body arrangement

In order to achieve cooling in an urban setting, certain physical conditions must be manipulated: orientation, canyon ratio, building spacing, and building geometry. These must create the condition for water to be under shade in order to decrease its surface temperature. Buildings must also slow down the wind and be arranged to minimise wind shadow and turbulence. See part A, B.

In the street condition B, cooling did not extend as much as expected despite having good wind velocity. This is due to the low canyon ratio, which exposes it to a high amount of radiation.

In addition, it is possible to cool beyond the frst row of buildings for up to 200 meters. This provides opportunity to place public functions there. However, in some areas cooling may happen due to very slow wind speed which is actually in the wind shadow of buildings. This may not have a signifcant impact on felt temperature. See part C. Thus, the ideal wind velocity would be from 1-4 m/s.

Experiment 3

Testing the impact of canyon ratio and street orientation on wind and radiation.

PHYSICAL CONDITIONS

Canyon Ratio

ENVIRONMENTAL CONDITIONS

The aim of this experiment was to identify which canyon ratio and street orientation would yield the ideal radiation and velocity.

This experiment was run parallel to Experiments 1 and 2. Both radiation and wind velocity play a major role in afecting the felt temperature. High radiation and high wind velocity have the potential to increase felt temperature above the air temperature; 45°C will feel like 48°C if radiation and wind are too high. Ideal radiation values were taken to be less than 3.33 kWh/m2, while wind was between 0.5 - 2 m/s. These values were extracted from vernacular precedents.

SET-UP

A 3d model of 180m x 180m was used as input. Building footprint size was 20m x 30m, and street width 45m based on a typical arrangement on site.

For radiation analysis the site location was set to be in Kuwait City on the hottest day, on August 14 from sunrise to sunset.

In CFD, the incoming wind was set at 2 m/s with the assumption that the wind would slow down from 7 m/s (hottest day condition) because of the surrounding built context.

Velocity 2 m/s, NWSE

Radiation: August 14 (hottest day)

Building footprint: 20 x 30

Street width: 45 m

VARIABLES

None of the canyons showed good radiation results. Shade was only acquired one the side. Even with a 3.o canyon ratio, a medium-high radiation level was achieved.

Canyon 2.0 was just above 3.33 kwH/m2

This orientation performs best, as most of the central area falls under low radiation.

A minimum canyon of 2.5 resulted in medium-low radiation levels in the center, with higher patches above and below it.

1. Street Orientation NS, NESW, EW, NWSE

2. Canyon Ratio 0.5, 1.0, 1.5, 2.0, 2.5, 3.0

Overall good wind fow, with some regions as low as 1.5 m/s. This implies a possibility of wind shadow.

Mixed zones are achieved here ranging from 2.5 m/s to 4 m/s. This falls within ideal range.

Buildings were able to block wind such that it is consistent throughout the center, at 2.3 m/s.

Overall, canyon ratios with the highest potential to decrease radiation and wind velocity were within the 1.5-2.5 canyon ratio range. For both radiation and velocity, streets with an East-West and NorthWestSouthEast orientation were best.

Although the remaining two orientations were not suitable for radiation, they perform well in terms of wind fow and thus have potential with some shading strategies.

Because the experiment was set without surrounding built context, the results are inaccurate. Depending on the surrounding arrangement, incoming wind may be faster or slower. However, conclusions can be drawn based on how each canyon-orientation combination performs in isolation.

Following these results and with the context of a typical neighborhood in mind, in principle streets should maintain a canyon ratio no less than 1.5 and no greater than 2.0. Furthermore, because the prominent wind direction comes from NorthWest-SouthEast, streets oriented in the opposite direction are not suitable. Therefore, strategies will be developed in order to best utilise streets in either a North-South, NorthWestSouthEast, and East-West orientation.

Wind velocity increased from 2 m/s to 4.57 m/s.

Experiment 4.1

Testing building arrangement preceding the wetland.

No. of Rows

BUILDING ARRANGEMENT

The aim of this experiment was to derive the number of building rows required with cool walls preceding a wetland such that it pre-cools the air to 40°C, and in what alignment (staggered vs. straight). This would maximize the cooling distance of the wetland.

In a 3d model, rows of buildings preceeding the wetland were arranged parallel to it. Rows succeeding it were arranged perpendicular, leaving a clear space to receive the cooling. Building footprint size was 20m x 30m, and street width 45m based on a typical arrangement on site.

For radiation analysis the site location was set to be in Kuwait City on the hottest day, on August 14 from sunrise to sunset.

In CFD, the model was oriented such that the wetland was perpendicular to the wind direction. The incoming wind was set at 5 m/s in order for it to decrease to approximately 2 m/s when incident at the wetland. Humidity was set at 6% and temperature at 45°C.

Velocity 5 m/s

Radiation: August 14 (hottest day)

Street width: 45 m

Orientation: perpendicular to wind

Air temperature: 45°C Humidity: 6%

3, 4, 5 wetland width: 25m

1. Number of rows preceding wetland

2. Building alignment straight staggered

Experiment 4.2

Testing the building arrangement preceding and following the wetland.

BUILDING ARRANGEMENT

No. of Rows Alignment closed end 2,4,3,5 straight, staggered CAPTURED COOLING PATTERN

This experiment was conducted similar to 4.1 with the introduction of a row of buildings at the receiving end to capture the cooling. The aim of this experiment was to derive the captured cooling pattern resulting from the diferent number of rows preceding the wetland.

Velocity 5 m/s

Radiation: August 14 (hottest day)

Building footprint: 20 x 30

Street width: 45 m

Air temperature: 45°C

Humidity: 6%

Orientation: perpendicular to wind

Rows of buildings preceding the wetland were arranged parallel to it. Rows succeeding it were arranged perpendicular, leaving a clear space to receive the cooling. Furthermore, a row of buildings at the end of the receiving end was added arranged perpendicular to the wind. Building footprint size was 20m x 30m, and street width 45m based on a typical arrangement on site.

For radiation analysis the site location was set to be in Kuwait City on the hottest day, on August 14 from sunrise to sunset. In CFD, the model was oriented such that the wetland was perpendicular to the wind direction. The incoming wind was set at 5 m/s in order for it to decrease to approximately 2 m/s when incident at the wetland. Humidity was set at 6% and temperature at 45°C.

1. Number of rows preceding wetland 2, 3, 4, 5

2. Building alignment straight staggered

Cool walls must be placed parallel to the wind direction to achieve maximum cooling. In addition where there are 5 building rows preceding the clearing a distance of 316 meters are cooled below 35°C. This shows that there is a signifcant amount of cooling to be captured.

Thus, in experiment 4.2 when the open space was created by closing the end cooling reached up to 208 meters. This divides the resulting cluster into two parts: an active cooling part (preceding wetland) and receiving end (after the wetland).

Since these rows work climatically but are too exaggerated for urban setting, an arrangement of 2 rows will be considered for site. This means that additional strategies to help cooling must be developed. Staggering of buildings prevents wind shadow. Cooling efect is expected to difer in orientations where the cluster is not aligned with the wind direction.

Experiment 5

Testing diferentiation of built morphology on shade.

Arrangement

BUILDINGS

Geometry

Orientation

Cluster Shape

Height

Top Profile Curve

1. To determine the height required to completely shade the ground area in diferent orientations in rectangular and square cluster arrangements.

2. To determine the height required to compeltely shade the same area with the extension of the building top profle curve in diferent orientations in rectangular and square cluster arrangements.

Velocity 5 m/s

Radiation: August 14 (hottest day)

Building footprint: 20 x 30

Street width: 45 m

Air temperature: 45°C

Humidity: 6%

Orientation: perpendicular to wind

RADIATION

Without top profile extension

VARIABLES

1. Orientation NS, NWSE, EW

2. Cluster Shape A- Rectangular 150m x 70m

B - Square 100m x 100m

Rows of buildings preceding the wetland were arranged parallel to it. Rows succeeding it were arranged perpendicular, leaving a clear space to receive the cooling. Furthermore, a row of buildings at the end of the receiving end was added arranged perpendicular to the wind. Building footprint size was 20m x 30m, and street width 45m based on a typical arrangement on site.

For radiation analysis the site location was set to be in Kuwait City on the hottest day, on August 14 from sunrise to sunset. In CFD, the model was oriented such that the wetland was perpendicular to the wind direction. The incoming wind was set at 5 m/s in order

CASE 1

Shape A - 150m x 70m Orientation - NS

Max. Height (floors): 76

Avg. Height (floors): 39 Volume (106 m3): 1.1

CASE 2

Shape A - 150m x 70m Orientation - NWSE

Max. Height (floors): 93

Avg. Height (floors): 40 Volume (106 m3): 1.2

CASE 3

Shape A - 150m x 70m Orientation - EW

Max. Height (floors): 80

Avg. Height (floors): 45 Volume (106 m3): 1.3

CASE 4

Shape B - 100 X 100 Orientation - NWSE

Max. Height (floors): 71

Avg. Height (floors): 32 Volume (106 m3): 0.9

3. Height

4. Top profile extension

CASE 5

Shape B - 100 X 100 Orientation - EW/NS

Max. Height (floors): 94

Avg. Height (floors): 49 Volume (106 m3): 1.2

Shape A - 150m x 70m Orientation - NS

Max. Height (floors): 39

Avg. Height (floors): 15 Volume (106 m3): 0.6 CASE 7

Shape A - 150m x 70m Orientation - NWSE

Max. Height (floors): 30

Avg. Height (floors): 15

Volume (106 m3): 0.6 CASE 8

Shape A - 150m x 70m Orientation - EW

Max. Height (floors): 37

Avg. Height (floors): 19 Volume (106 m3): 1.1 CASE 9

Shape B - 100 X 100 Orientation - NWSE

Max. Height (floors): 26

Avg. Height (floors): 14

Volume (106 m3): 0.6

CASE 10

Shape B - 100 X 100 Orientation - EW/NS

Max. Height (floors): 58

Avg. Height (floors): 24

Volume (106 m3): 1.0

The best case scenario for a rectangular confguration is Case 7, where the volume and height was the least. For a square confguration Case 9 was able to shade the ground with 0.6 volume.

Thus, with a profle extension of up to a maximum of 2x it was possible to reduce the average height of buildings to half to completely shade the ground.

Because building volume adds heat, for site intervention additional shading strategies can be added so that radiation is taken care of collectively and distributed between orientation, building morphology and placement of trees.

Since in high density cities there is a demand higher built density there is a compromise on intensity where buildings should have cool walls regardless of the presence or absence of trees. Spatially, this allows for continuous space. Meanwhile in lower densities, trees can achieve higher cooling intensity within a space. However, this will result in a more divided or interrupted space.

Experiment 6

Testing the impact of orientation and building type on radiation and velocity within a cluster.

INTRODUCTION AIM

In order to intensify and extend the cooling contained within a cluster, maximum shade must be achieved. This is accomplished through the collective shading contributed by building geometry and the distribution of trees.

Each cluster is made up of 14 buildings with several parameters: each building can vary in height, top extrusion, and bottom recession. The top extrusion increases the shaded area, while the bottom recession increases the amount of shaded usable space and spacing between each building. This would decrease radiation and impact wind velocity. Because built mass contributes to the heat, the total volume of buildings within a cluster must be minimised. Moreover, the spacing between buildings on the outgoing end of the cluster must be less than at the incoming end in order to capture the cooling.

In areas not shaded by the buildings, trees or wetland extensions are allocated to compensate. Thus, shading from the buildings and introduction of trees and wetland extensions lower the ambient temperature, increase cooling intensity, and increase the shaded public space. Consequently, a variation in cooling intensity and pattern results. This was tested for the North-South, Northwest-southeast, and East-West orientations.

Therefore, clusters were generated using a genetic algorithm that aimed to:

1. Minimise radiation

2. Minimise building volume

3. Maximise the spacing between buildings at the incoming end of the cluster.

The algorithm was set to run for 300 generations, to be sampled at every 50 generations. The solution converged after 150 generations, which meant that the sample taken at the 300th generation was the best combination with the given constraints. Therefore, when tested in CFD the cooling pattern that resulted would represent the cluster’s maximum cooling potential. Three clusters - one for every orientation - were obtained.

1. Generate the combination of building geometries that would provide maximum shade for a minimum set volume

2. Locate trees and wetland extensions where they would be most efective in terms of shade and the decrease in air temperature

such that it intensifes cooling within the cluster and extends beyond it.

VARIABLES

1. Built Morphology

Height

Top profile extrusion

Bottom profile recession

2. Cluster orientation

North-South

NorthWest-SouthEast East-West

PRE-SETS

Velocity 5 m/s

Radiation: August 14 (hottest day)

Air temperature: 45°C

Humidity: 6%

Number of iterations: 300

Conclusion

The maximum area shaded by trees is in the east west confguration. This is ideal since areas that receive higher radiation would need a greater amount of evaporative cooling to ofset. It also means that since a larger volume of air has been cooled more intensely a larger secondary space is possible. Areas that fall between the 35-38 temperature range have potential cooling.

For each orientation it tends to cool approximately 250300m distance in wind direction, which provides an opportunity for a secondary extension. This implies an aggregation pattern on site. With the right aggregation a larger area can be cooled and brought down to 30-35c.

Pattern (CFD in Appendix)

Conclusions & Strategies

Extending cooling - Patterns

Water bodies in a certain arrangement and size have the potential to cool up to 200-300 meters on site. In summary, there are several rules to take into consideration before aggregating UCIs on site:

1. Wetlands should have a minimum width of 20 meters to cool sufciently. However, a wetland can be divided into segments given that the distance between each is no more than 10 meters. This extends cooling.

2. Buildings must be arranged such that they slow down wind passing over the water body.

3. In order to achieve maximum shade with minimal built volume (therefore minimising the heat generated by building materials) the extension of the building profle is necessary. The same area can be shaded with half the built volume and height.

4. Cool walls parallel to the wind maximise its cooling distance.

5. A cool island comprises of two parts: an active cooling part (cool walls and wetland) and a receiving end. To obtain maximum cooling in the receiving end, the air must be precooled using buildings with cool walls before air reaches the wetland.

6. To further minimise built volume and ensure maximum shaded ground area, shading can be achieved partially by buildings and partially by the introduction of shade trees.

The next phase will be directed at answering the following:

1. At which temperature range can cooling be achieved while to reduce cool walls to 1-2 rows to increase efciency on site?

2. What is the trade of between the cooling efciency and cooling intensity?

3. What are possible strategies of aggregating UCIs on site?

4.To what extent (radius) can each UCI cool?

5. How do they work in a group?

An integrated water route is proposed in order to combine cool walls, vegetation, greywater from the city and wetlands into a cycle. Halophytes in the wetlands treat and flter incoming greywater, and then feed it to the cool walls, and tree trenches to green the city. Extra water is once again returned to the wetland.

This creates a cooler microclimate within the city. The water is supplied in the form of greywater from domestic and commercial use after a preliminary fltration treatment. This system can allow the cool islands to be dispersed in the city and gives more fexibility to chose strategic locations for efective cooling.

Cleaned water is stored in tanks and distributed in the ceramic pipe system for ʻvertical coolingʼ

Preliminary greywater treated from city

Bioremediated water feeds pipes in cool walls

constructed wetlands (horizontal subsurface) provide bioremidiation to clean grey water before it is supplied to cool walls and tree trenches.

Dense arrangement of halophytes increased the surface area for transpiration and provides cooling along its length

Tree trenches are a system of trees connected by an underground infiltration structure. The pipe carrying bio-remidiated water from the wetlands is placed in a stone/ gravel bed and the water permeates into the layer of soil above it for root-uptake. This provides an opportunity for larger shade trees while remidiated water improves soil quality by nitrogen fixing

Design Proposal

Test Case: Kuwait City, Kuwait

Site Selection Criteria

Kuwait City’s districts fall under three main categories: business,mixed use and residential. The business district is comprised of high rise buildings concentrated in certain areas with wide spaces in between. Mixed use areas have mid to high rise buildings with occasional spacing, but overall tend to be more densely packed. Residential areas have uniformly distributed low rise buildings, with a central open space. Based on the experiments, UCIs require areas where the built is continuous, with small voids between 0.5 and 1.2 hectares. Surrounding buildings are necessary to slow down the wind,

Business District

Tall buildings, large open spaces

Programs: ofce and commercial Grey water generation

Green belt

Large park surrounding downtown, with a total area of 235,500 m2

Residential Neighbourhood

Uniform low density

Residential, amenities, schools

Grey water generation 140 liters per person per day population: 31,500

while the spaces in between allow for insertion of the UCIs. Thus, the test case area was chosen to be in Aldasmah, a residential neighborhood along with Bneid Algar, a mixed use neighborhood along the coast. Typical building heights in Aldasmah range from 2.5 to 3 foors, while in Bneid Algar most buildings range from 7 to 20 foors. The total area is 2.5 km2.

Site conditions

Extracted Site Parameters and Givens

For the purpose of testing the UCI cooling potential, only specifc site conditions were taken into consideration: the solar path, wind direction and velocity, air temperature, and the average height of the surrounding built morphology. The surrounding building heights would then inform the higher limit to which buildings in the cluster would be allowed to rise. This is to have a more spatially viable height diference, as well as to avoid wind turbulence outside the cluster. cities, the road network was not addressed, and since the main aim is to achieve cooling is beyond the scope of the research. Any built volume within 100m of the cluster center has been redistributed and added to the cluster volume. Thus a part of the buildings on site are left intact.

Kuwait has the highest consumption of freshwater per capita per year in the world. Refer to Appendix for water consumption and efciency rates.

Kuwait temperatures average 30°C or above 6 months during the year, from May to October. For those months, temperatures can rise above 40°C, and up to 45°C from June to August. With the given current urban fabric, cooling 45°C requires more than an insertion of a cool island.

As concluded from previous experiments, cooling an area sufciently for a 45°C day requires 5 rows of buildings with cool walls, which is not viable. As a result, it is more suitable to aim for ameliorating conditions that precede the hottest day conditions. See fgure 1.3. This would mean that instead of August, the new target is June when average temperature is 40°C. All evaluations following will be measured against climatic conditions on June 10.

Locating UCIs

Locating Potential Intervention Spots

When locating UCIs on site, unbuilt areas that would be under shade are frst identifed. This is accomplished by taking unbuilt residual space that is within a 50-meter ofset from the surrounding buildings. This would prevent the cluster from also being isolated.

These areas are then converted into nodes, each representing a potential UCI.

Each node then locates its nearest group of buildings on each side (North, south, east, West). Each node must have buildings located in the direction of the wind, or within a 15 degree variation. The nodes are fltered based on this condition.

The remaining nodes then are oriented in the alignment closest to the wind vector, and thus resulting in an orientation.

Each orientation is then assigned a cooling radius (assumed from the results of the experiments chapter).

Nodes with an overlapping radii are then eliminated, allowing only one of them to become a UCI. The resulting nodes become the UCI locations, while the other ones remain just nodes. Because their locations are also strategic and will receive cooling, they become points at which the wetland network must pass.

Wetlands are then located at the appropriate edge of each footprint, perpendicular to the wind direction.

From the center of each UCI, the next nearest Island is identifed. The UCIs re-align themselves within a +- 45 degree deviation from the wind direction such that they are not oriented at sharp angles in relation to each other and maintain a visual connection.

The wetland then passes through each UCI and the nodes to create the wetland network.

Depending on the surrounding built context, a height limit is assigned to each cluster. Since in experiment 6 average height limits were 30 foors, these numbers were halved here in order to observe the amount of vegetation that would result to compensate for the area not under shade. Hence, depending on its location on site, and orientation, each cluster would be limited to a certain height,

The aim for each cluster is to achieve maximum shading while minimising the total volume of the cluster.

Built Morphology

Strategies for decreasing radiation and built volume

In order to achieve maximum shading with minimal built volume, the built morphology underwent a series of operations (primary variables) that would allow the top profle to extend and bottom profle to recess. This would provide self and ground shading, and release a secondary level of public space. These operations are the minimal needed for the necessary shading. Supplementary to the primitive variables, additional operations can be added to further sculpt the building to increase shading efect. Of the variations, the third type was selected and used in the cluster generations.

Geometry

Variables

Since the full shade is only obtained when the buildings are in a cluster, they will be evaluated collectively in cluster generations for average height of buildings within the cluster, area shaded by buildings, and space in between each building.

UCI generation

Results

For each orientation, maximum shading was achieved with the least possible built volume. Any residual areas out of shade, within a radiation range greater than 4.0 kwh/m2 were compensated by shade trees.

It is apparent in the results that the trade of was between the width of the cluster and its height. Clusters with a square confguration were shorter, with less vegetation. However, UCI 9 in the East-West orientation had a signifcant area of vegetation. This is ideal since areas that receive higher radiation would need a greater amount of evaporative cooling to ofset.

Clusters with a rectangular confguration could go higher and require little vegetation, like UCI 4 or cantilever forward with lower buildings like UCI 8.

Depending on the vegetation pattern, an inference on the divisions of space on the interior can be made and therefore matched with a compatible program. For example, UCI 3 implies a clear division in the center, suggesting a bufer zone between two programs.

Shape A - 150m x 70m

- NS Max. Height (floors): 76

(10 m3): 1.1

Shape A - 150m x 70m

- NS

Max. Height (floors): 76

(106 m3): 1.1

Shape A - 150m x 70m

- NS

Wind Velocity & Air Temperature Results

Due to software limitations, the site had to be divided into 4 zones and simulated separately. The zones were divided such that most clusters were still in a group, as the cooling is infuenced collectively. Cooling is more intense for clusters within a 200 meter distance from each other. In some areas it was possible for cooling to extend and cool beyond the UCI, into the extension. This cooling should be a driver for a secondary pedestrian network in order to take full advantage and allow comfortable circulation.

ZONE 1

ZONE 4

ZONE 2

ZONE 3

ZONE 1 ZONE 2

ZONE 4

3

Cooling Patterns

Cooling was the most intense in Zone 3, largely because the air was of a lesser temperature by the time it reached it as it had already passed over Zone 2. On average, cooling distances were within the 200 meter range. However, in areas where clusters form “pockets” such as in Zone 4, the graph illustrates a larger distance of cooling in the middle and a decrease towards the end.

Though it may bring temperatures down by 3°C around it, the climatic impact is still good enough only to cool the area within. However, strategic placements of diferentiated sizes and within certain distances may be able to bring down the ambient temperature of the city if applied throughout.

ZONE 1

ZONE 2

ZONE 3

ZONE 4

Resulting Felt Temperature (PET) Program Integration

Felt Temperature (PET) Within Each UCI

The spatial distribution within a UCI should be informed by program and its requirements. This includes the circulation pattern, in addition to its potential to attract large, medium, or a small concentration of people. High activity programs generate more heat, and often require a larger space. This would require a calibration between shading requirements, spatial division and area, and to combine activities of diferent intensities to maintain a heat balance within the space.

Related Programs Program vs. Activity Pattern

UCI Analysis

The total area of distributed UCIs is approximately 20 Ha, equivalent to the size of the Green Belt. Collectively, the UCIs provide 65 Ha of more usable space as opposed to the unusable 20 Ha concentrated in the Green Belt. This arrangement proves to be a more suitable and efcient option for public space for cities in the hot, arid region. The following chart compares diferent physical confgurations of each UCI and their climatic impact, and ultimately their resultant felt temperature (PET).

Physical Descriptors of the UCI

Conclusions

Overall Conclusions

Overall, the cooling achieved was sufcient only on a local scale. All of the Cool Islands were able reduce air temperature within the 30°C range within their cluster, and only some were able to cool their extensions as well. Therefore, the cooling captured is sufcient to provide a comfortable environment within. Some UCIs, however, were able to cool up to 150 meters beyond the extension such as cluster 8. Though the cooling is not uniformly distributed, it shows potential of further aggregation development and strategies in order to intensify, capture, or extend it. Furthermore, since the extension is also directional, it can be utilised as a driver for generating an emergent secondary pedestrian network (cool corridors) while the wetland can provide the main pedestrian route. In that way the cooling extension patterns can be used to lure pedestrians within the UCI.

The total area of distributed UCIs is approximately 20 Ha, equivalent to the size of the Green Belt. Collectively, the UCIs provide 65 Ha of more usable space as opposed to the unusable 20 Ha concentrated in the Green Belt. This arrangement proves to be a more suitable and efcient option for public space for cities in the hot, arid region.

Though the cooling is non uniformly distributed in all directions, it provides an opportunity to be a driver to generate an emergent secondary pedestrian network alongside the primary network along the wetland.

When grouped, UCIs operate more efectively. For example, the group formed by clusters 8, 9, and 10 showed a possibility of intensifying the cooling. Although the cooling in cluster 10 is not as great, it manages to ameliorate conditions such that 8 and 9 are cooler as a result of its presence. This could inform the type of function that could occur within a UCI, alternative strategies (i.e. ground recession), and at the same time the minimum percentage of vegetation required to intensify the cooling in such a condition.

UCIs that were within 200 meters of each other had a joint cooling efect on the surrounding pathways, and were able to result in emerging cool spots in transitioning spaces. This would have the potential of creating more casual social locations en route to destinations. Furthermore, wind fow is enhanced when UCIs are in a group, due to the diference between the width of the buildings at one exist and the next entrance. Though the relative diference in velocity is 0.5 to 1 m/s, locally this can provide a pleasant current of air movement throughout the space. in contrast to what is outside.

Within the UCI, air temperature is reduced to 30°C. This value represents a value at an instant, at a particular location in the centre of the space. Radiation, temperature, and humidity values will vary throughout the day and thus afecting the felt temperature. According to the generated results, the felt temperature within an Island ranges from 28 - 30°C. However, due to the addition of shade trees, the spatial perception of the space

will be even more drastic in comparison to conditions outside the Cool Island.

As a result of a diferentiation of the proportion of ground cover across the site, and hence possible activity patterns, a programmatic variation occurs. Zoning also occurs in a vertical direction with the introduction of secondary public spaces. This enhances the visual connection and programmatic combinations concentrated within a single space.

The temperature of the city is not to be considered as that of the climate; it partakes too much of an artifcial warmth, induced by its structure, by a crowded population, and the consumption of great quantities of fuel in fres.

- Iain D. Stewart

Critical Review & Further Development

The outputs generated in this research yielded fairly accurate results given the assumptions when compared with scientifc literature. The biggest limitation, however, was that these tools were not in the same computational environment. The process had to be divided into separate phases, with principles carried forward instead of real time results. A faster, more comprehensive way of simulating it would mean that CFD and radiation would directly inform each other. When placed together in a genetic algorithm, a larger variety of options can be generated. It would also allow a more controlled way of setting limits on diferent parameters to observe patterns over a large number of generations which would reveal key relationships between diferent trade-ofs. Both Ecotect and Simulation CFD are by Autodesk, yet they are completely independent platforms. This would result in a much more informed design decision and stronger relation to a context on site.

In this research, the UCIs were based on a 1-hectare patch, which is the largest size viable given the climatic conditions in this region. The arrangement tested on site was one outcome using the maximum size UCIs. This is not necessarily the most efective in terms of cooling. It is probably more efcient to use diferentiated sizes. In proportion to the size of the surrounding neighbourhood, 10 UCIs of this size are likely too large as they require a much larger fow of people to be activated. This would mean that if 1-hectare is the upper limit, it should be placed in prominent intersections within a network. This would require larger distances to be cooled. The rest of the UCI distribution should be diferentiated, relating the scale to the number of people it may cater to in addition to its cooling efect. Thus, a trade-of between cooling efciency and intensity arises. Collectively, it is crucial to understand the pattern or distribution that would yield the highest impact on the overall ambient temperature, while still maintaining quality of space.

In order to reach the full potential of the UCI, the city fabric must accommodate itself to it on more than one scale. Activation of public space involves several layers: thermal comfort, connectivity, and program. In this research, the frst tier has been addressed with outcomes suggesting on how to address the remaining factors. The most crucial, perhaps, is that the spatial consequence of a UCI is driven by trade-ofs.

Comparison With Scientific Literature Cooling Extent: Size

Source

Location of Study

Claim

Scientific Literature

The Impact of Green Areas on Site and Urban Climates

Haifa, Israel

“The temperature gradient outside the 0.5 ha Benjamin Park was about 1.5°C and extended up to 150 m”

GIVONI, B. (1998). Impact of green areas on site and urban climates (Chapter 9). In: B. Givoni ed. Climate considerations in building and urban design. J. Wiley & Sons, New York. pp.303–30.

Source

Location of Study

Claim

Urban Cool Islands

The temperature gradient from the edge of the wetland to the end of the area of potential cooling is approximately 3°C and is 250 - 300 m on average. At this rate, if only the cooled areas were to be considered, the gradient would also be 1.5C extending over an area of 125 to 150 m.

Simulation of thermal effects of urban green areas on their surrounding areas.

Kamumoto City, Japan

“a 100 m wide greenspace cools to a distance of 300 m and a 400 m wide greenspace cools to a distance of 400 m. Greenspaces should be no more than 300 m apart for optimum cooling within a neighbourhood.”

HONJO, T. and TAKAKURA, T. (1990–91). Simulation of thermal efects of urban green areas on their surrounding areas. Energy and Buildings 15, 443–6.

The most optimum cooling was achieved by islands located within 200 - 250 meters from each other.

Heat Generated by Built Volume vs. Shade Created

Building volume generates heat, which increases the felt temperature within the space. Though this was not considered in the calculations, the built volume was minimised. Thus, in clusters where vegetation is very low, it becomes even more essential that building material should be of low albedo. Masdar institute provides some precedent where they have reduced the interior building cooling demand by 70% by using materials containing low thermal mass. Although cool walls have a potential to reduce surface temperature by 12°C, complementary strategies must be developed in addition. For example, fenestrations should be placed to only capture indirect daylighting since there is an abundance of sunlight hours throughout the year to decrease the heat load. A balance between the amount of shade a building creates vs. the heat it generates is crucial and requires the application of the Cool Island constituents on diferent scales.

Cooling Intensity Required vs. Built and Population Density

Relative to their size, UCIs require a minimum of medium built density to function, and depending on the climate, cannot be in high density areas. This is due to the heat generated by built environment, and the anthropogenic heat due to a large concentration of people. For a city like Kuwait, it suggests a tradeof between the size of the UCI, the strength of its program, and the surrounding built density. For more prominent UCIs, the cooling extension becomes just as important in order for people to be able to walk there. Additionally, for maximum cooling intensity for the UCI to be achieved there should be a fair built density but not so much that it begins to reverse the cooling. This calibration is crucial to explore, as it will inform the sequence and distribution of density and inform the overall approach to urban planning for cities in this context.

This would set a quantifed relationship between the built volume, and the necessary amount of vegetation to of-set it/cool the space given a specifed building material. It is also important to understand if these numbers are possible within a 1-hectare space, and how it can be spatially organized. how much vegetation is required to ofset the built volume? and is it viable i.e. high density (and needed ground area that cannot be given to trees?

Network

The surface temperature of a vehicular road in dry temperatures can be up to 3C hotter than non vehicular roads. (Fujimoto, Watanabe, and Fukuhara 2008). In addition, cars emit pollution and contribute greatly to refecting heat. This is especially true for cities where the car is the main mode of transport. This means that the proximity of the vehicular network

to the UCI creates an adverse efect. In the region, it is not uncommon for every person to own a private car within each household which has led to the oversaturation of the existing road network and a constant trafc congestion. One approach to minimise the heat generated and alleviate trafc is to investigate the potential of an underground public transport network. Further, the above ground pedestrian network should emerge from the cooling patterns.

Wetland System

In this research, the potential of the halophytes to treat greywater has been used. However, some species of halophytes also have the potential to treat saltwater such that by the end of the cycle the water is nonpotable but signifcantly less saline. This can address the high energy consumption rates of water that need to be desalinated, and where large quantities of salt are emptied into the sea. Building upon this, a backward loop can also be looked into where seawater fows through the wetland, and can undergo part of the desalination process. This will help conserve the large amount of energy spent by desalination.

In conclusion, this research develops a basic methodology that begins to address the struggle of outdoor conditions for cities in hot and arid climates. UCIs set a basis for the appropriate scale and potential magnitude of cooling within the region. This informs the spatial organisation within and around it. More signifcantly, when simulating the resulting wind fow and air temperature, the method proposed in this thesis is comparative to other scientifc literature making it a viable and accessible tool for architects, engineers, and planners.

CFD analysis for air temperature and wind speed

MAPS

Experiment 3.2

Addressing wind turbulence

Wind turbulence in between buildings of a cool island can cause discomfort. In order to address this, experiments were carried on 7 diferent building footprints modifed to be chamfered or rounded or both. These were tested for canyon ratios 1.5 and 2 in 4 orientations. As the set-up model lacked surrounding built areas, the results obtained were not conclusive. Furthermore, turbulence between building would not have a signifcant impact on the cooling with in a cluster. This would require experimenting at the building scale while the initial experiments of the UCIs were carried out at cluster scale. Hence, further developments to this experiment were suspended.

Experiment 3 Results

Experiment 3 Setup

Canals

Experiment 3.2

Addressing wind turbulence

Experiment 3.2

Addressing wind turbulence

Water calculations

Grey water generation

Grey water cycle

Cooling efficiency

Based on greywater available and public space requirements of Kuwait

COOL ISLANDS

Experiment 1.2

Addressing wind turbulence

Experiment 1 Setup

Experiment 1 Results

Assuming, 0.3m deep water bodies and that the water is replaced weekly, 476 million liters can cover an area of

If all the public spaces were to be cooled using evaporative

the efficiency of each cool island should be

Social Mapping

Studying Kuwait’s demographic range and their activity pattern

Demographic distribution - Ages Time spent at a specific program through the day

High Income group

Mid Income group

Low Income group