INTEGRATED BIOCLIMATIC DESIGN AT URBAN SCALE

Dr. Niki Gaitani, Prof. Mattheos Santamouris

Group of Buildings Environmental Studies

Physics Department

National & Kapodstrian University of Athens

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Climate Change

Projections of extreme temperatures as represented by the combined number of hot summer (June-August) days (Tmax>35C) & tropical nights (Tmin>20C)

Source: Fischer and Schär, 2010

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Key Observed & Projected Impacts from Climate Change for the main regions in Europe

Source: European Environment Agency (EEA), 2012c

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Potential Impact

IN GREECE: A. Changes in annual mean temperature of

more than 3.5 degrees Celsius B. The number of sunny days exhibit increases

of more than 40 days per year on average C. Decrease in summer precipitation of up to

40%

Hot spots are mostly in the South of Europe

The annual number of days above 37C and 40C is increasing

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Heat waves

Source: The European Environment Agency, 2012. Heat waves - both a low share of green & blue urban areas & high population densities contribute potentially to the urban heat island in cities

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Urban Heat Island

•City size & Urban Polulation

•Climate, Topography, Physical Layout

Modification by urban areas:

•Radiative

•Thermal

•Moisture

•Aerodynamic characteristics

http://www.ides-edu.eu/ Copyright 2014 IDES-EDU

Factors determining the strength of the UHI & its impacts

Source: European Environment Agency (EEA), 2012c

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Urban Adaptation to Climate Change

Adaptation & Mitigation the way towards a more sustainable & resilient future for people & nature

Adaptation also relates strongly to using & expanding green infrastructure such as parks, forests, wetlands, green walls and roofs, wherever feasible & sustainable serves to provide a cooling effect on cities as well as playing a role in managing floods

Support from a national and European framework is crucial in assisting cities to adapt

Traditional measures

Innovative solutions

¾ of the population of Europe live in urban areas & this is where climate change will be most apparent in everyday life

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Bioclimatic Design

Knowledge of prevailing climate conditions

Analysis & understanding of landscape data

Methods for applying this knowledge, through landscape design, to create microclimate that are comfortable for people & minimize the energy use of buildings

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Microclimatic Modifications

http://www.ides-edu.eu/ Copyright 2014 IDES-EDU

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Thermal Comfort

http://www.ides-edu.eu/ Copyright 2014 IDES-EDU

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Techniques to Mitigate Urban Heat Problems

1 •Reduce solar radiation using shading techniques

2 •Increase reflected radiation using light colors

3

•Use cool materials with high reflectivity and emissivity

4 •Change inclination of surfaces

http://www.ides-edu.eu/ Copyright 2014 IDES-EDU

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Microclimatic Design

Parks & Green Spaces Permeable Surfaces

Materials Trees http://www.ides-edu.eu/ Copyright 2014 IDES-EDU

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Adaptation Measures

cool cool

standard standard

25 30 35 40 45 50 55 60 65 70

(x 0.67 km)

10

15

20

25

30

35

40

45

50

(x 0.6

7 km)

ΔΤ (o

C)

-3.0

to -

1.5

-1.5

to 0

.0

0.0

to 0

.5

0.5

to 1

.0

1.0

to 1

.5

1.5

to 2

.0

2.0

to 2

.5

2.5

to 3

.0

“Cool” materials characterized by high reflectance to short wave radiation & high emissivity to long wave radiation

The use of cool materials at city scale can contribute to the reduction of air temperature

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Integrated Approach

A. Field measurements microclimatic data (Tair, Wind, Humidity, Tsurf)

B. Study the role of the materials used in the

urban fabric (IR)

C. Investigation of thermal comfort in

outdoor spaces (Bioclimatic indices)

D. Integration of microclimatic

information in the design of open spaces

E. Evaluation of proposed solutions with bioclimatic CFD models

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Case study: Historic center of Tirana (1)

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Case study: Historic center of Tirana (2)

The use of passive cooling techniques involving cool materials, solar control and additional vegetation as well as earth to air heat exchangers can reduce the peak summer ambient temperature up to 3 degrees, while surface temperatures are decreased up to 6-8ºC

Bioclimatic design of open public spaces in the historic centre of Tirana, Albania (2011) SUSTAINABLE CITIES & SOCIETY, 1 (1), pp. 54-62. Fintikakis, N., Gaitani, N., Santamouris, M., Assimakopoulos, M., Assimakopoulos, D.N., Fintikaki, M., Albanis, G., Papadimitriou, K., Chryssochoides, E., Katopodi, K., Doumas, P

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Case study: Marousi (1)

3rd Palenc, 5th EPIC & 1st Cool Roofs Conference, 29 Sept-1 Oct, 2010, Rhodes, Greece, Strategies for microclimatic modifications in the urban spaces-Marousi center, Greece, N. Gaitani, A. Spanou, M. Saliari, M. Santamouris , F. Xyrafi

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Case study: Marousi (2)

3rd Palenc, 5th EPIC & 1st Cool Roofs Conference, 29 Sept-1 Oct, 2010, Rhodes, Greece, Strategies for microclimatic modifications in the urban spaces-Marousi center, Greece, N. Gaitani, A. Spanou, M. Saliari, M. Santamouris , F. Xyrafi

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Challenges & Opportunities for Cities

•Local city characteristics tend to be highly important in terms of sensitivity to heat •The results suggest that cities designed in such a way that makes them susceptible to heat are not unique to one particular region •It is highly likely that the length, frequency and/or intensity of heat waves will increase • Present day design of many cities with few green urban areas but many artificial surfaces aggravates the impact of heat waves within cities, in particular by increasing night-time temperatures • City governments have a range of options at their disposal to be better prepared for future heat conditions, including 'grey', 'green' and variety of 'soft' solutions

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Thank you!

Photos: Dimitris Messinis

ngaitani@phys.uoa.gr