Microclimatic Studies in the Greek Urban Environment: A Case Study in Thessaloniki

MICROCLIMATIC STUDIES IN THE GREEK URBAN ENVIRONMENT: A CASE STUDY IN THESSALONIKI Olga Tsagkalidou

Architectural Association School of Architecture | Graduate School AA SED MSc + MArch Sustainable Environmental Design 2014 - 2015 | Research Paper 2 | April 2015

Microclimatic Studies in the Greek Urban Environment: A Case Stuty in Thessaloniki

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Architectural Association School of Architecture Research Paper 2 | MSc + MArch Sustainable Environmental Design 2014 - 2015

Microclimatic Studies in the Greek Urban Environment: A Case Stuty in Thessaloniki

AUTHORSHIP DECLARATION FORM

Research Paper 2

TITLE: Microclimatic Studies in the Greek Urban Environment: A Case Study in Thessaloniki

NUMBER OF WORDS: 3.642

STUDENT NAME: Olga Tsagkalidou

DECLARATION: “I certify that the contents of this document are entirely my own work and that any quotation or paraphrase from the published or unpublished work of others is duly acknowledged.”

Signature:

Date: 27 April 2015

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Microclimatic Studies in the Greek Urban Environment: A Case Stuty in Thessaloniki

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Architectural Association School of Architecture Research Paper 2 | MSc + MArch Sustainable Environmental Design 2014 - 2015

Microclimatic Studies in the Greek Urban Environment: A Case Stuty in Thessaloniki

TABLE OF CONTENTS ABSTRACT 1. INTRODUCTION 2. THE URBAN CLIMATE

2.1. The Urban Energy Balance

2.2. The Urban Canyon

2.3. The Urban Heat Island 3. THE GREEK URBAN ENVIRONMENT

3.1. The typical Greek Urban Block

3.2. A Case Study in Thessaloniki: Navarinou Neighborhood 4. CLIMATE ANALYSIS 5. FIELDWORK

5.1. Urban Canyon Spot Measurements

5.2. Rooftop Spot Measurements

5.3. Comparative Assessment 6. DESIGN GUIDELINES 7. CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES

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MSc DISSERTATION PROJECT PROPOSAL

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Architectural Association School of Architecture Research Paper 2 | MSc + MArch Sustainable Environmental Design 2014 - 2015

Microclimatic Studies in the Greek Urban Environment: A Case Stuty in Thessaloniki

ABSTRACT Contemporary cities experience poor urban environment conditions. High densities have resulted in the genesis of the Heat Island effect that under the undeniable climate change will only get intensified. Reducing the ambient temperatures and improving the microclimate inside the urban fabric appears to be urgent. This paper examines the parameters affecting the urban microclimate. Through the analysis of a typical urban block and the process of fieldwork in the city center of Thessaloniki, urban geometrical characteristics and environmental conditions are identified. Possible design guidelines aiming to rehabilitate the urban block are also evaluated.

Keywords: urban heat island, microclimate, high density, urban energy balance, urban canyon, rooftops, materiality, green roofs, cool materials

1. INTRODUCTION

Over the past decades, cities have experienced a rapid urbanization and industrialization that have caused degradation of the urban environment. Especially in Greece, this major urban growth is characterized by an uncontrolled development which shaped the chaotic high density city centers. The construction boom taken place in large cities and the increasing densities have resulted in higher temperatures in the built areas compared to the surrounding suburban and rural areas (Santamouris et al, 2001). The phenomenon is called the ‘urban heat island’ and is strongly linked to the indisputable climatic change (Santamouris, 2012).

Massive urban blocks, scarcity of open and social spaces, lack of vegetation and trees, air pollution, increased noise levels and augmented electricity peak loads are all evident in most of the worldwide urban environments (Gartland, 2008). Therefore, the need to study the urban climate and understand its complex microclimatic conditions is undeniable and also proven by the large number of the existing studies.

Particularly in Greece, the high ecological footprint of the Greek cities establish the importance of larger scale interventions and the deficient conditions of the social space raises questions for the regeneration of the public areas. Taking, also, into consideration the forthcoming climate change, the projected rise of the ambient temperatures and the lack of green spaces, the improvement of the microclimate1 inside the cities and the mitigation of the urban heat island seem to be urgent.

2. THE URBAN CLIMATE

The urbanization process has altered the natural characteristics of the Earth’s surface and as a result it interferes in the energy balance of the environment through the transformation of the radiative, thermal, moisture and aerodynamic characteristics of an area (Oke, 1987).

Oke (1987) divides the atmosphere above the city into two layers (Figure 2.0.1.): • The Urban Boundary Layer (UBL), is the lower part of the troposphere that is affected by the built environment over time periods of about one day.

• The Urban Canopy Layer (UCL), the lowest part of the urban atmosphere, starting from the ground level and extends up to the buildings’ roof level.

Due to the innate heterogeneity of the UCL, condiErell et al (2011) defines the microclimate as the climate that prevails at the micro-scale level.

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tions inside the cities vary from one point to another, resulting in the creation of distinct but coexisting microclimates inside the urban fabric (Erell et al, 2011).

Figure 2.0.1.: Schematic section of the urban atmosphere showing the urban boundary layer and the urban canopy layer. (Source: Erell et al, 2011)

2.1. The Urban Energy Balance

According to the First Law of Thermodynamics that states that energy is always preserved and constantly changing from one form to another, the urban energy balance is summarized by the equation (Santamouris et al, 2001): Energy Gains = Energy Losses + Energy Storage2 The nature of the materials of the environment and especially their albedo and their emissivity has a significant impact to the urban energy balance (Santamouris et al, 2001). Figure 2.1.1. represents detailed urban energy balance processes for the city of Athens.

Figure 2.1.1.: Urban energy fluxes in a typical urban block in Athens and calculations of heat loads. (Source: Kapsali, 2012) The equation can be converted into Q* + QF = QH + QL + QS (Oke, 1987) specifying the radiative and anthropogenic heat gains, sensible via convection and latent via evaporation or evapotranspiration heat losses and the remaining absorbed and stored energy into the urban elements.

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Microclimatic Studies in the Greek Urban Environment: A Case Stuty in Thessaloniki

2.2. The Urban Canyon

In order to describe the density and the physical properties of the city, quantifiable measures should be considered (Erell et al, 2011). One of most common and useful one is the urban canyon, whose geometry is defined by three factors: • The height-to-width ratio (H/W), describing the proportions of the average buildings’ height to the width of the street.

• The axis orientation (θ), describing the direction of the canyon and measured usually in degrees.

• The sky view factor (SVF), which is the proportion of the sky dome that is ‘seen’ by a surface or a point.

Figure 2.2.1. shows that the higher the H/W ratio the less the SVF leading to a restricted viewable unobstructed sky from the ground. Cheng et al (2006) found out that a random city layout compared to a more uniform one is more favorable in terms of ‘ground openness’.

records from weather station inside the urban fabric are 5–15 K higher than the ones from suburban stations (Santamouris et al, 2001).

The more influential factors of the Heat Island are summarized by Oke et al (1991) and they refer to the canyon radiative geometry, the thermal properties of materials, the anthropogenic heat, the urban greenhouse effect, the reduction of evaporative surfaces and the reduced turbulent transfer. Erell et al (2011) mentions that although the phenomenon can also be recorded during the day, most commonly is evident during night times. Apart from the discomfort conditions, both indoors and outdoors and the augmented cooling loads, raised temperatures also engender decreased performance of the mechanical cooling systems and increased air pollution and ozone concentrations (Santamouris, 2012). The efficiency of passive cooling ventilation techniques, like the night ventilation, is also compromised (Santamouris et al, 2010).

The most efficient mitigation strategies involves solar control, the characteristics of the urban materiality, the expansion of vegetation inside the city fabric and the use of natural heat sinks to dissipate surplus heat (Akbari, 2007).

3. THE GREEK URBAN ENVIRONMENT

Figure 2.2.1.: Diagram showing the relation between the height-to-width ratio and the sky view factor in a rectangular courtyard. (Source: Erell et al, 2011)

Urban airflow in the UCL in a very complex phenomenon. Wind speed and direction are extremely variable (Santamouris et al, 2001). In general, the wind speeds of the urban UCL are considerably lower compared to the ones in the UBL, but local geometries and micro-scale elements may result to higher wind speeds (Erell et al, 2011).

Greek cities, especially Athens and Thessaloniki, experienced a major urbanization movement during the 1950s after World War II. The regulative framework between 1946 and 1984 shaped the city centers as they are known nowadays (Figure 3.0.1). The main characteristics of the urban environment are the high density urban blocks, the lack of vegetation, the insufficient social spaces, the fragmented open public spaces and the existence of great traffic congestion, noise and air pollution. The city of Thessaloniki, located in northern Greece, is a coastal Mediterranean city that during the 1950s urban growth, experienced a major residential problem which led to the construction of an average 8-storey high apartment buildings in the city center. The most common street axis orientations that forms the grid hosting urban blocks are 40°SE and 40°NE or 15°NW and 75°NE (Theodosiou et al, 2005).

2.3. The Urban Heat Island

The significant air temperatures difference which is found between urban areas and their surrounding rural ones is defined as the Heat Island phenomenon and its cause is the changes in the urban energy balance made by human activity (Erell et al, 2011; Gartland, 2008; Oke, 1987; Santamouris et al, 2001). The intensity of the phenomenon may reach up to a 15 K difference. In the city of Athens, studies have revealed that the temperatures 08

Figure 3.0.1.: Aerial perspective of the city of Thessaloniki in northern Greece. (Source: www.123rf.com)

Architectural Association School of Architecture Research Paper 2 | MSc + MArch Sustainable Environmental Design 2014 - 2015

Microclimatic Studies in the Greek Urban Environment: A Case Stuty in Thessaloniki

3.1. The typical Greek Urban Block

Figure 3.1.1.: The Square Block typology in Athens. (Source: Google Earth)

The legislative framework and constant revisions of the General Building Code of 1929 led step by step to an increased plot coverage of 70% having as a result high density urban blocks with a continuous outline along the street network (Pantazi, 2010). The ‘continuous building system’ has its roots in the period of 1957 – 1985 and resulted in attached buildings side by side and united street façades. Consequently, the 30% of the uncovered space was always left at the rear part of each plot. The addition of these ‘leftover’ void spaces created a type of inner-block courtyards in order to provide daylight to the rear façades of the apartment buildings and without any social usage (Kapsali, 2012). Another important feature of the Greek urban blocks is the accumulation of the flat roofs of each building. Although, they are used as spaces for maintenance and they lack any design attention, the roof level provides an extensive layer in the city with great environmental and social potential (Vlachou, 2011). Figures 3.1.1. and 3.1.2. represent the two main urban block typologies3 that can be found in the Greek city centers. The studies focused on the city of Athens, which shows a higher layout uniformity than Thessaloniki’s.

3.2. A Case Study in Thessaloniki: Navarinou Neighborhood

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ICH

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I. M

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Figure 3.1.2.: The Rectangular Block typology in Athens. (Source: Google Earth)

Following the consulted literature and aiming to assess the microclimatic conditions in the city of Thessaloniki, an urban block in the city center was selected to be studied and analyzed (Figure 3.2.1.). Navarinou is one of the oldest, densest and lively areas of Thessaloniki. The area also has a great historical importance because of the existence of the ruins of the Galerius’ Palace and the nearby Arch of Galerius and the Rotunda Church, all of them originated from the 4th century.

The corner apartment building in the intersection of D. Gounari and I. Michail streets and its rooftop was selected in order to conduct fieldwork. The urban block is similar to the Square typology which can be found in Athens, but bigger with its sides dimension reaching 70m by 70m. The void percentage accounts for the 14.5 % of the total block area.

Aiming to understand the density of Thessaloniki’s city center, it seemed valuable to identify the geometrical characteristics of the urban block in relation to the adjacent streets and buildings. The average height of the buildings nearby is 9-storeys high, which corresponds to a 30m height. The width of D. Gounari pedestrian street (Figure 3.2.2.) and I. Michail (Figure 3.2.3.) street is 25m and 10m respectively, which consequently accounts for a 1.2 and 3 Vlachou (2011) and Vogiatzi-Tamba (2009) describe the spatial characteristics of the two urban block typologies in Athens. The Square Block’s dimensions vary from 40-50 m, the H/W ratio ranges from 0.75 to 2 and the void percentage is around 6.5 – 25 % of the total block area. The Rectangular Block’s dimensions is approximately 40 – 50 m by 80 – 100 m, the H/W ratio ranges from 0.2 to 0.4 and the void percentage is 10 – 28 %. The average building height in Athens is generally 5 to 7 storeys.

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Figure 3.2.1.: Case Study’s urban block in Navarinou Neighborhood in the city center of Thessaloniki. (Source: Bing Maps)

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Microclimatic Studies in the Greek Urban Environment: A Case Stuty in Thessaloniki

Figure 3.2.2.: D. Gounari pedestrian street. Part Figure 3.2.3.: I. Michail street. (Source: Author) of the ruins of the Galerius Palace can be also seen. (Source: Author)

(a) D. GOUNARI

(b) I. MICHAIL

Figure 3.2.4.: Case Study’s urban block void courtyard. (Source: Author)

(c) CROSSROAD

(d) COURTYARD

Figure 3.1.5.: Sky view factors for (a) D. Gounari: 0.28, (b) I. Michail: 0.15, (c) Crossroad: 0.33 and (d) Courtyard: 0.04. (Source: Ecotect)

Figure 3.2.6.: Corner apartment building roof- Figure 3.2.7.: Corner apartment building roof- Figure 3.2.8.: The view from the rooftop towards top. Staircase - lift canopy. (Source: Author) top. (Source: Author) the old town of Thessaloniki. (Source: Author)

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Microclimatic Studies in the Greek Urban Environment: A Case Stuty in Thessaloniki

H/W ratio. The courtyard’s (Figure 3.2.4.) average H/W ratio is 5.3. It is already obvious that the urban environment of the city center is really dense, a fact that it is also proven by the calculation of the Sky View Factor for the two streets, their intersection and the urban block’s courtyard (Figure 3.2.5.). I. Michail street has a 40°SE axis orientation and respectively D. Gounari a 40°NE, resembling the majority of the urban blocks’ orientation in Thessaloniki’s city center (Theodosiou et al, 2005).

According to Theodosiou et al (2005), the building facades in the city center, regardless of their orientation, do not have adequate solar access during winter due to the overshadowing effect (H/W >> 1), while in summer the adjacent buildings do not provide effective shading. The limited solar access in winter and the unobstructed solar exposure in summer also affect the ground floor open outdoor spaces, creating an uncomfortable environment.

The rooftop of the apartment building occupies a 165 m2 floor area. It is used only for maintenance without any other design intention. Antennas, solar collectors and cables running through the space could even make it quite dangerous. Vertical elements, like the main staircase-lift canopy or partitions and elements of the adjacent rooftops, provide shading at some parts for certain hours during the day. Finally the views from the rooftop towards the city are impressive (Figures 3.2.6., 3.2.7. and 3.2.8.).

Figure 4.0.2.: Prevailing winds in Thessaloniki. (Source: Weather Tool)

Figure 4.0.3. shows the sunshine availability throughout the year. Overcast sky conditions can be observed only for 17 % of the year, whereas for the 62 % Thessaloniki is in favor of clear skies.

4. CLIMATE ANALYSIS

Thessaloniki is a coastal city located in the northern part of Greece at 40.5°N latitude and 23.0°E longitude and lies in the 3rd climatic zone according to the national Technical Directive of the Technical Chamber of Greece (TDTCG 20701-1, 2010).

The annual cycle of the climate of Thessaloniki, a Mediterranean climate (Figure 4.0.1.), can be divided into three periods, a warm summer from June until September, a moderate period during April, May and October, and a cold winter from November until March. Average coldest days during winter may reach up to -3°C, whereas during summer average hottest days rise higher than 35°C. Spring and autumn in general provide acceptable outdoor comfort conditions (Chatzidimitriou et al, 2004), whereas winter and summer are a challenge.

The prevailing winds during winter are NW and can be quite strong, whereas the rest of the year SE winds prevail. The average wind speed inside the urban fabric is around 2.0m/s (Figure 4.0.2.).

Figure 4.0.1.: Monthly temperatures of Thessaloniki. (Source: Meteonorm)

Figure 4.0.3.: Frequency of Night, Sunny, Intermediate and Cloudy skies (%) from Sunrise to Sunset in Thessaloniki. (Source: Satel-Light)

The weather data were acquired from Thessaloniki’s Airport weather station, using Meteonorm. ‘Makedonia’ Airport is located 15 Km SE of the city center in a very low density area. During the fieldwork the indication of the heat island effect has been examined.

5. FIELDWORK

Aiming to assess the microclimatic conditions around the selected urban block fieldwork has been conducted during 15th April. The spot-measurement readings have been also compared with the air temperature records for the respective day and times from the ‘Makedonia’ Airport weather station. These data were acquired from the W-Underground web site.

Spot measurements were taken in the D. Gounari and I. Michail street, on their intersection and on the rooftop of the corner apartment building. The monitoring was

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Microclimatic Studies in the Greek Urban Environment: A Case Stuty in Thessaloniki

carried out throughout the day, in morning hours (10:00 am), in the afternoon (15:00 pm) and at night (22:00 pm).

During the period of fieldwork the access inside the courtyard was not possible.

The sky conditions during the day were sunny and clear. Illuminance levels, as expected, were found to be high around 80 – 95 Klux under the unobstructed sky.

Ground floor values were always around 10 Klux lower than the rooftop ones. Values taken in shadowed spots, without any direct solar radiation, were significantly decreased.

5.1. Urban Canyon Spot Measurements

Results (Table 1) showed that the peak air temperatures on the ground level occurred in the afternoon.

The readings were at 15:00 pm ranged between 22.1°C – 24.2°C, whereas in the morning the average measured air temperature was around 20°C. At night, the air temperatures dropped significantly, ranging between 16.1 – 17.3°C. A 5 - 8 K difference was observed between afternoon and night measurements, while the difference between morning hours and night was around 1 – 5 K.

The range of the relative humidity throughout the

day was 16.9% - 41.7%. During morning hours humidity levels were around 20%, dropped a little as the day passed and reached around 40% during night. Having in mind that Thessaloniki has a quite humid climate, the particular day of the fieldwork does not apply to this fact.

Wind speed found to be quite reduced inside the canyons with the measurements ranging from 0.2 – 1.5 m/s.

5.2. Rooftop Spot Measurements

Table 2 shows the results of spot measurements taken on the rooftop. Peak air temperatures were observed again during afternoon hours and they ranged from 24°C to 26.5°C, while morning ones were around 18°C – 21.5°C. Night time temperatures were also reduced reaching 15.2 - 16°C.

Relative humidity ranged between 20 – 43.3% throughout the day, while the wind speeds were not high as firstly expected due to the higher level, being around 0.2 – 2 m/s.

Surface temperatures were also taken on the rooftop, following the consulted literature that mentions the importance of materiality especially in the most exposed

Table 1: Ground level spot measurements (air temperature, relative humidity, wind speed) taken during fieldwork on 15th April.

Table 2: Rooftop spot measurements (air temperature, relative humidity, wind speed) taken during fieldwork on 15th April.

Table 3: Rooftop surface temperatures taken during fieldwork with spot measurements on 15th April.

Figure 5.2.1.: Bitumen roofing sheets (dark grey Figure 5.2.2.: Color coating used for waterproof- Figure 5.2.3.: Concrete (light-colored) used on tar) used for waterproofing. (Source: Author) ing. Dirty and damaged. (Source: Author) vertical surfaces. (Source: Author)

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Microclimatic Studies in the Greek Urban Environment: A Case Stuty in Thessaloniki

areas of the city. Table 3 summarizes the results. Three materials were used mostly on the rooftop. Half of the rooftop floor was covered with bitumen roofing sheets (dark tar) for waterproofing reasons (Figure 5.2.1). On the other half a waterproof color was used, originally white-colored but currently dirty and damaged (Figure 5.2.2.). The vertical built elements were concrete which was painted in a light color (Figure 5.2.3).

Results show that all three materials’ temperatures peaked in the afternoon. The dark bitumen sheets reached 51°C, the color coating 41.5°C, while the concrete reached 36.5°C. During morning hours the surface temperatures were respectively 40.2°C, 26.5°C and 26.3°C. These measurements correspond to the exposed surfaces. On the other hand surface temperatures taken in shadowed areas were substantially reduced. At night all surface temperatures dropped to 12.3-12.6°C.

Apparently, the natural characteristics of the materials determine to a great extend their behavior. The dark bitumen, having a lower albedo than the more reflective light-colored ones, heated up more and peaked at almost 10 K higher than the light-colored coating, even though the performance of the latter must have been compromised due to the dirt and damage.

5.3. Comparative Assessment

It is notable that during the day the rooftop receives more incident solar radiation, especially in the afternoon, and therefore in general higher air temperatures occur, compared to the ground level ones inside the canyons. In the morning the air temperature inside the urban canyons compared to the rooftop’s one is more or less at the same levels. In the afternoon, due to the overshadowing effect of the adjacent buildings, the difference between ground level and rooftop air temperatures is on average around 2 K. At night temperatures drop both at ground level as well as at roof level. Temperatures inside the urban canyons are a bit higher than the rooftop ones at night, indicating a difficulty of dissipating excess heat due to low sky view factors.

The air temperatures taken inside the urban fabric are always higher compared to temperatures records from the suburban ‘Makedonia’ Airport weather station. The greatest variations are found during the night reaching a maximum of a 6.3 K difference. The indication of a heat island effect is undeniable.

Wind speeds in the city both at ground level as well as on the rooftop are generally reduced, not exceeding a value of 2.0 m/s. Rooftop level air velocities appear to be a bit higher than the relevant ones in the urban canyon, but this observation should not be immediately generalized. Rooftop canopies, antennas, local micro-scale geometries may result in low air velocities on rooftop level as well. More extensive measurements in the area and CFD analysis should be made in future assessments in order to form an accurate outcome.

6. DESIGN GUIDELINES

In order to find the appropriate design guidelines firstly to improve the microclimate in situations like the Case Study and consequently to mitigate the urban heat island, published literature was consulted. The use of ‘cool’ materials of high albedo, the expansion of vegetated spaces, solar control and improvement of the air-flow are the most efficient bioclimatic design strategies (Akbari, 2007; Axarli et al, 2012; Gaitani et al, 2007).

Many recent studies focus on the materiality of rooftops and the performance of various cooling techniques. Alexandri et al (2006) analyzes the efficiency of four different roof typologies compared to a typical concrete base case. The ‘green sky’ (a vegetated pergola) and the green roof seem to have a greater effect on decreasing temperatures than the pond or the white-coated concrete roof. In general, all four performed better than the base case.

It is also found that after some years of the application of ‘cool’ coatings, their albedo lowers by 25%, resulting in a 57% decrease in their performance (Alexandri et al, 2006). Nowadays, new cool colored materials, that have the ability to reflect the infrared radiation, are under development (Synnefa et al, 2007).

A study conducted on the planted roof of the Ministry of Finance and Economics in Athens (Rogdakis et al, 2008) shows that the surface temperature of the green roof never exceed 37°C in comparison with the unplanted surfaces which reached 50°C. Vegetation and evaporative areas (Figure 6.0.1.) appear to be very effective techniques to deal with the urban heat island and have an essential impact both on the roof level as well as well above the roof level (Alexandri et al, 2006). Lowering the air temperature in the boundary layer allows the impact of the green roofs, when applied in a larder urban scale, to extend to the ground level as well. The effect of the green roof on the ground level can be enhanced if it would be combined with the planting of courtyards (Vlachou, 2011).

Figure 6.0.1.: Implementing green roofs combined with vegetated courtyards. (Source: Vlachou, 2011)

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Microclimatic Studies in the Greek Urban Environment: A Case Stuty in Thessaloniki

ACKNOWLEDGEMENTS I would like to thank all the AA Sustainable Environmental Design teaching staff and visiting lectures and especially my tutor Simos Yannas for his support and guidance during the RP2 tutorials. I would also like to thank Mariam Kapsali for her help during my research. Special thanks are attributed to Stratos Apostolidis for his help during fieldwork.

REFERENCES •

Akbari, H. (2007). Opportunities for saving energy and improving air quality in Urban Heat Islands in Advances in Passive Cooling. pp.30-93. Earthscan. London.

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Alexandri, E., P. Jones. (2006). Ponds, Green Roofs, Pergolas and High Albedo Materials; Which Cooling Technique for Urban Spaces?. PLEA 2006. Geneva.

In terms of improving the air-flow inside the urban fabric, creating openings on ground level (Figure 6.0.2.) increase both the wind speeds as well as the temperature variations in the urban voids (Chatzidimitriou et al, 2004).

Implementing pilotis in every building of a broader area found to have unpleasant effects for pedestrians. Openings should be decided carefully after a CFD analysis.

During winter protection strategies from cold winds should also be considered (Kapsali, 2012).

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Axarli, K., A. Chatzidimitriou. (2012). Redesigning Urban Open Spaces Based on Bioclimatic Criteria: Two squares in Thessaloniki, Greece. PLEA 2012. Lima.

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Chatzidimitriou, A., S. Yannas. (2004). Microclimatic Studies of Urban Open Spaces in Northern Greece.

PLEA 2004. Eindhoven.

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Cheng, V., K. Steemers, M. Montavon, R. Compagnon. (2006). Urban Form, Density and Solar Potential.

PLEA 2006. Geneva.

7. CONCLUSIONS

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Erell, E., D. Pearlmutter, T. Williamson (2011). Urban Microclimate Designing the Spaces Between Buildings. Earthscan. London.

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Gaitani, N., G. Mihalakakou, M. Santamouris. (2007).

On the use of bioclimatic architecture principles in order to improve thermal comfort conditions in outdoor spaces. Building and Environment. Journal 42. pp 317-324. Elsevier.

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Gartland, L. (2008). Heat Islands. Earthscan. London.

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Kapsali, M. (2012). Refurbishing the Urban Blocks in Central Athens. MSc. Thesis. Sustainable Environmental Design Programme. AA Graduate School.

London.

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Oke, T.R. (1987). Boundary Layer Climates. Cambridge University Press. Cambridge.

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Oke, T.R., G.T. Johnson, D.G. Steyn, I.D. Watson.

(1991). Simulation of Surface Urban Heat Islands under ‘Ideal’ Conditions at Night – Part 2: Diagnosis and Causation in Boundary Layer Meteorology. Vol.56. pp.339-358.

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Pantazi, K. (2010). Urban metaphors. Exploring the

Figure 6.0.2.: Implementing pilotis to improve urban air-flow. (Source: Kapsali, 2012)

Improving the microclimate inside the dense city centers appears to be emerging in order to deal with urban heat island effect and its results, consequently to reduceing the enormous carbon footprint of the cities. Where urban planning policies failed, environmental interventions can alleviate the poor conditions of the urban environments.

In Greece, special attention should be given to the rehabilitation of the typical urban block and the regeneration of the neglected void and open spaces. Even in extreme situations, like the Case Study in Navarinou Neighborhood in Thessaloniki, where the urban geometry is already pre-defined design strategies can be found. Replacing the existing materials with more permeable and porous ones and using light colors on rooftops can have very good environmental results. The implementation of green roofs and the use of vegetation have the capability of reducing air temperatures both at meso-scale as well as at urban scale.

Given the limited free ground level area, the rooftop level of the city provides a new layer where the application of appropriate interventions may produce socially and environmentally active spaces. Such a holistic and strategic design plan can upgrade the quality of life in the city by not only improving outdoor comfort conditions, but also having a beneficial impact on the indoors environmental performance.

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urban Roofscape of Athens. March Thesis. Sustainable Environmental Design Programme. AA School of Architecture. Graduate School. London.

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Rogdakis, E., I. Koronaki, D. Tertipis. (2008). Assessment of green roof installation on the building of the ministry of finance and economics. NTUA, School of mechanical engineering, Section of Thermal Engineering Laboratory of Applied Thermodynamics.

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Santamouris, M. (Ed. 2001). Energy and Climate in the Urban Built Environment. James & James (Science Publishers) Ltd. London.

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Santamouris, M. (2012). Cooling cities – A review of reflective and green roof mitigation technologies to fight heat island and improve comfort in urban environment.

Solar Energy. Journal 103. pp 682-703. Elsevier.

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Santamouris, M. A. Sfakianaki, K. Pavlou. (2010). On the efficiency of night ventilation techniques applied to residential buildings. Energy and Buildings. Journal 42. pp 1309-1313. Elsevier.

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Synnefa, A., M. Santamouris, H. Akbari. (2007). Estimating the effect of using cool coatings on energy loads and thermal comfort in residential buildings in various climatic conditions. Energy and Buildings.

Journal 39. pp. 1167-1174. Elsevier.

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Technical Chamber of Greece. (2010). Energy Performance of Buildings Directive. Technical Guidelines T.O.T.E.E. 20701-1/2010. Guidelines on the evaluation of the energy performance of buildings (in Greek).

Theodosiou, T., N. Chrisomallidou. (2005). Shading and Solar Availability in the Urban Environment. PLEA 2005. Beirut.

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Vlachou, H. (2011). Leftovers. Exploring the environmental potential of roofs and urban voids in Athens. MSc. Thesis. Sustainable Environmental Design Programme. AA Graduate School. London.

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Vogiatzi-Tamba, A. (2009). Transforming the Urban Void to an Urban Scene. MSc Thesis. Sustainable Environmental Design Programme. AA School of Architecture. Graduate School. London.

INTERNET http://www.satel-light.com http://www.wunderground.com TOOLS Ecotect Analysis 2011 Meteonorm V7.1.2.15160 Weather Tool 2011

Architectural Association School of Architecture Research Paper 2 | MSc + MArch Sustainable Environmental Design 2014 - 2015

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MSc Dissertation Project Proposal

Descriptive Title Looking at the Big Picture: Environmental retrofit of the unexploited roofscape of Thessaloniki Overview The uncontrolled urbanization that took place over the past decades in the Greek cities resulted in the dense urban environment we encounter today. Past legislative framework formed certain urban block typologies, consisting of a poor quality building stock and deficient outdoor void spaces. Taking, also, into consideration, the undeniable heat island effect, the forthcoming climate change and the lack of green spaces, the improvement of the microclimate inside the city appears to be urgent.

Under these circumstances, the rooftop level of the city provide a new layer of unused and overlooked space, where environmental design strategies can be applied, aiming the rehabilitation of the urban block and finally an urban scale regeneration. Two different, in terms of geometry, density and materiality, urban blocks in Thessaloniki will be examined. The first one (Figure 01) is located in the dense historic center of Thessaloniki, whereas the second (Figure 02) is in Vyzantio neighborhood in the eastern part of city.

urban geometry should also be considered as a probable solution in extreme cases and have to be examined. The roofscape of the city seems to have great environmental potential for such interventions. The question of inserting a new habitable layer in the city is raised.

Scale is a really important aspect affecting the overall study. Applicability regarding the micro-scale urban geometries, the urban block and neighborhood, the city, even different parts of the country, Thessaloniki and Athens, will be investigated.

Methodology

Term 2 Research Paper focused on the analysis of microclimatic conditions of the urban block in the center of Thessaloniki, followed by possible improvement design guidelines. Different types of Heat Island mitigation techniques were researched.

Materiality appears to have a significant role, especially in a predefined urban geometry. The effectiveness of green roofs, adaptive shading canopies and high albedo coatings need to be assessed in greater depth in the context of different climatic conditions. Small changes in the

The main parameters affecting the urban climate and design strategies will be identified through literature review in the upcoming weeks. Having as a starting point precedent studies in the Greek urban environment and especially in Thessaloniki, possible interventions aiming to improve the microclimate will be decided.

Fieldwork will take place during July. More extensive measurements will take place in the urban block in the city center of Thessaloniki (Figure 01). The selection of the second study block in Vyzantio (Figure 02) incorporates some of the design guidelines, ground level vegetation and pilotis, identified in Term 2 Research Paper, which will be examined. A comparative assessment between the two areas will occur. Fieldwork will also take place in the city of Athens to identify the differences in the urban climate in different parts of the country.

Through analytic work the potential solutions and difficulties of the proposed applicable interventions will be assessed. Part of the research and the methodology is the step-by-step comparison with the relative dissertation of

Figure 01: Case Study 1: Urban Block in the city center of Thessaloniki, Navarinou neighborhood. (Source: Bing Maps)

Figure 02: Case Study 2: Urban Block in the eastern part of Thessaloniki, Vyzantio neighborhood. (Source: Bing Maps)

Research Questions – Hypothesis

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Architectural Association School of Architecture Research Paper 2 | MSc + MArch Sustainable Environmental Design 2014 - 2015

MSc Dissertation Project Proposal

Avgousta Stanitsa, referring to the city of Athens.

Expected Outcome Applicable design strategies, focusing a city’s roofscape and aiming to improve the city’s microclimatic conditions and the urban climate in general, are expected to be found.

The social regeneration of the leftover outdoor spaces and the creation of habitable conditions will be important aspects of this research too.

References •

Cadima, P. (2000). Transitional Spaces: the potential of semi-outdoor spaces as a means for environmental control with special reference to Portugal. PhD Thesis, Environment and Energy Studies Programme. AA School of Architecture. Graduate School. London.

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Chatzidimitriou, A. (2003). ‘Urban Voids’ The sustainable potential of void open spaces in contemporary urban environment in Thessaloniki. MA Thesis. Environment and Energy Studies Programme.

AA School of Architecture. Graduate School. London.

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Erell, E., D. Pearlmutter, T. Williamson (2011). Urban Microclimate Designing the Spaces Between Buildings. Earthscan. London.

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Gartland, L. (2008). Heat Islands. Earthscan. London.

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Kapsali, M. (2012). Refurbishing the Urban Blocks in Central Athens. MSc. Thesis. Sustainable Environmental Design Programme. AA Graduate School.

London.

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Oke, T.R. (1987). Boundary Layer Climates. Cambridge University Press. Cambridge.

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Pantazi, K. (2010). Urban metaphors. Exploring the urban Roofscape of Athens. MArch Thesis. Sustainable Environmental Design Programme. AA School of Architecture. Graduate School. London.

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Santamouris, M. (Ed. 2001). Energy and Climate in the Urban Built Environment. James & James (Science Publishers) Ltd. London.

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Vlachou, H. (2011). Leftovers. Exploring the environmental potential of roofs and urban voids in Athens. MSc. Thesis. Sustainable Environmental Design Programme. AA Graduate School. London.

•

Vogiatzi-Tamba, A. (2009). Transforming the Urban Void to an Urban Scene. MSc Thesis. Sustainable Environmental Design Programme. AA School of Architecture. Graduate School. London.

Architectural Association School of Architecture Research Paper 2 | MSc + MArch Sustainable Environmental Design 2014 - 2015

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