Abolin Co: Urban Heat Island - An Eye On Materials

Urban Heat Islands

BASIC DESCRIPTION, IMPACTS AND MITIGATION TECHNOLOGIES

www.abolinco.com

An EYE on Reflective Building Materials Available Technologies and Benefits

P.Perdikis

Basic Description

BACELONA DECEMBER 2014 ABOLIN CO

Areas in and around cities are generally warmer than

comparable rural areas.

Urban development reduces vegetative cover and adds heat absorbing surfaces such as rooftops, buildings, and paving.

Heat is also added from other

sources in cities such as fuel combustion and air conditioning units.

The result is an urban heat island.

http://geographyfieldwork.com/BarcelonaHeatIsland.htm

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Types of Urban Heat Islands


Three types: surface, canopy, and boundary layer:

Surface heat islands Higher surface temperatures in urban areas compared with

rural areas.

Atmospheric heat islands

Warmer air in urban areas compared with rural areas,

Canopy layer heat islands are present in the air layer where we live

– from ground level to the tops of trees or buildings.

Boundary layer heat islands are in the area above rooftops and

trees extending upwards as much as 2 Km.

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Surface and Atmospheric Heat Islands


Feature Surface UHI Atmospheric UHI

Timing • Present all times day or night • Most intense during daytime

and summers

• Small or absent during day • Most intense at night or just

before dawn and in winter

Peak Intensity More spatial and temporal variation

Less variation

Typical Method for Identification

Indirect measurements using remote sensing

Direct measurements with weather stations or mobile measurements

Typical Illustration

Thermal image Isotherm maps & temperature graphs

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Surface and Air Temperatures


Day Temperatures

Day surface temperatures vary widely by surface type.

Day air temperatures vary much less.

Night Temperatures

Night surface temperatures are hotter over urban surfaces.

Night air temperatures follow the same pattern as surface temperatures.

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How do heat islands form?


Primary Drivers

Vegetation

Shade Moisture

Urban surfaces

Thermal properties Land cover

Urban geometry Dimensions and shape

of buildings

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Vegetation and Heat Islands


Trees and vegetation provide shade which help lower surface temperatures.

They also release water to the air (evapotranspiration), which helps cool the

area.

Urban areas have more dry, un-shaded surfaces (paving and rooftops), which

evaporate less water.

Highly developed urban areas, which are characterized by 75%-100% impervious surfaces, have less surface moisture available for evapotranspiration than natural ground cover, which has less than 10% impervious cover.

This characteristic contributes to higher surface and air temperatures in urban areas

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Surfaces Impact on Heat and Runoff


30% evapotranspiration

10% shallow infiltration 5%deep

infiltration

40% evapotranspiration

25% shallow infiltration

25% deep infiltration

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Urban Surfaces


Properties of urban materials

Reflectivity is a material’s ability to reflect

solar radiation; also called albedo

Thermal emittance is a material’s ability

to release heat; also called emissivity

Heat capacity is a material’s ability

to store heat

Extent of Urban Coverage Trees/vegetation: ? Roofs: ? Paving: ? Barren soil/other:? “Roofs and pavements cover about 60 percent of urban surfaces, and absorb more than 80 percent of the sunlight that contacts them”. http://coolroofs.org/documents/GCCAOverview_May2011.pdf

Colored Cool Roof in Barcelona

Intensive coverage with rooftops and paving

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Urban Geometry .1


Dimensions and spacing of buildings affect urban temperatures, affecting:

Wind flow

Energy absorption

Solar radiation back into space

Downtown high rise buildings shade surfaces during the day, helping to cool the area, but at night, wind flow is reduced and energy absorbed during the day is released.

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Urban Geometry .2


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Urban Canyon

The geometry of urban roads is such that often the term attributed "urban canyon", since morphological approach, the natural canyon.

Urban Canyon


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Urban canyons have an impact on different local conditions such as:

temperature, which can rise 2-4 degrees

contribute to the emergence of the phenomenon of urban heat island

atmospheric quality of the area: the local stagnant air collects pollutants near the ground level

the wind speed

Why do we care?


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Greater amounts of energy use during the summer Increased air pollution and greenhouse gas emissions Negative effects of higher temperatures on human health and comfort Warmer stormwater runoff affecting water quality

• Higher urban temperatures mean:

Energy Use


Peak electricity demand increases up to 5% for every 1ºC increase in summer temperatures.

Higher temperatures result in higher electricity bills.

For large cities, this higher demand is 5 to 10% higher to offset heat island effects.

Peak load use of electricity is higher, placing pressure on the power grid and greater demand for additional power plants.

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Air Quality


Higher electric power demand increases emissions from power plants, including increased carbon dioxide emissions.

Higher temperatures enhance urban ozone formation.

Higher temperatures increase evaporative emissions, adding volatile organic compounds (VOCs) to the air.

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Human Health and Comfort


• Higher daytime and nighttime temperatures affect human health, including general discomfort, respiratory difficulties, heat cramps, heat strokes, and heat related mortality.

• Urban heat islands make extended heat waves more damaging, particularly to sensitive populations such as children and older adults.

Key message: Increasing temperatures are likely to increase the number of heat-related deaths. Mortality risk increases by between 0.2 and 5.5 % for every 1 C increase in temperature above a location-specific threshold.

Temperature-mortality relationship

http://www.eea.europa.eu/data-and-maps/indicators/heat-and-health

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Water Quality


High surface temperatures transfer excess heat to stormwater runoff into streams, rivers, and lakes.

Temperature increases can be as high as 5ºC in 40 minutes of a heavy summer rain.

This thermal pollution impacts water quality by damaging aquatic life in the affected waterways.

http://stormwater.safl.umn.edu/updates-february-2009

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How to Reduce Heat Island Impacts


Three fundamental methods:

1. Trees

Protection and additional planting trees and vegetation

Use of shade trees for energy benefits

2. Reflective Surfaces

Increased solar reflectivity of urban surfaces

Cool roofs Ѵ

More reflective paving materials…

3. Water Related Effects

Increased evaporative capabilities of urban surfaces, which also benefit stormwater runoff and water quality

Green roofs

Porous paving

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1.0 Trees


Trees have a cooling effect because of shade and the moisture transpired through leaf surfaces.

Trees decline in numbers primarily through urban development, but equivalent amounts of trees are not replaced.

Tree maintenance and protection

Conservation and maintenance of existing trees are essential to avoid increased heat island effects over time.

Tree planting

Tree planting during development and redevelopment is critical to achieving a viable urban tree population.

On-going public and private sector initiatives are needed, with active encouragement of planting by homeowners and property owners.

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1.1 Shade Trees


Trees located in the right spots to shade homes reduce energy costs and increase property values.

Street trees and trees in parking areas help reduce temperatures and contribute to the quality of life in cities.

Source: Trees and Vegetation, 2008, Reducing Urban Heat Islands: Compendium ofStrategies, U.S. EPA, p. 4.

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2.0 Reflective Surfaces


Rooftops and pavement comprise most of the surface area covered by urban development.

More reflective materials are available for many roofing and paving applications.

2.1 Cool roofing

2.2 Cool paving

2.3 Cool facades?

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2.1 Cool Roofing


Rooftops comprise 20 to 25% of developed urban areas.

Surface temperatures of reflective roofs are much cooler, reducing heat island effects.

Before: Barcelona, black modified bituminous roof. 2014.

Barcelona, Colored COOL ROOF based on Abolin Co Coatings Tech. 2014.

HOT

COOL

Surface Temperature:

77,9 ºC

Surface Temperature: 47,4 ºC

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2.2.1 Cool Paving


Paved surfaces can be the largest portion of urban land cover, amounting to 30 to 45% of developed areas.

Pavement stores heat during the day and releases it at night.

Surface temperatures do not reach temperatures as hot as rooftops.

More reflective pavements are available, but not yet widely used.

Porous/pervious paving is also part of urban heat island mitigation.

COOL PAVING COATING

Product

BLC Blue 21

BLC Blue 42

BLC Green

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BLC Brown

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BLC Yellow Brown

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BLC Dark

Yellow 10

BLC Bright

Yellow F

BLC White

New

Asphalt Aged as-

phalt

SRI: Solar Reflectance index

32 40 40 42 50 71 78 107 1 15

TS: Surface Temperature 70,2 OC 67,2 OC 67,2 OC 66,7 OC 63,7 OC 55,4 OC 52,8 OC 42 OC 81,9 OC 78,1 OC

COLOURS

Surface Temperature Reduction in Comparison to New Asphalt

- 11,7 OC - 14,7 OC - 14,7 OC - 15,2 OC - 18,2 OC - 26,5 OC - 29,1 OC - 39,9 OC

Surface Temperature Reduction in Comparison to Aged Asphalt

- 7,9 OC - 10,9 OC - 10,9 OC - 11,4 OC - 14,4 OC - 22,7 OC - 25,3 OC - 36,1 OC

Note: Calculation Tool coded By Ronnen Levinson Heat Island Group (http//heatisland.lbl.gov

From 7,9 ºC up to 39,9 ºC Surface Temperature difference in comparison to black asphalt.

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2.2.2 Cool Paving


Cool Barrier Pave Coating: Fulfills the requirements acc to En 1871 –Road Marking Materials

Suitable for use on both asphalt and concrete

Can be easily formulated with high mohs hardness functional fillers for excellent abrasion resistance depending on product application use.

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2.3.1 Cool Facades


Building Exterior Walls comprise a very high percent of the developed build environment.

“In urban environment, the use of these coating techniques for facades is as important as for roofs, especially in dense cities. When the urban structure is characterized by narrow street canyons, the radiation trapping increases the surface temperature and the reduced airflow recirculation leads to higher air temperatures” (http://www.sciencedirect.com/science/article/pii/S0378778811005263)

The use of a cool selective paint on street facades reduces the air temperature within the street by about 1.5°C (http://www.sciencedirect.com/science/article/pii/S0360132306003957)

The daily variation of the effective albedo of a street canyon depends not only on the H=W ratio but also on the other factors, e.g. the combination of the reflectivity of the street and walls, the azimuth of the canyon, season of the year and the latitude of the location. (http://link.springer.com/article/10.1007%2Fs00704-007-0312-6#page-1)

Surface temperatures of reflective walls are much cooler, reducing heat island effects and energy used for cooling.

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http://www.sciencedirect.com/science/article/pii/S0378778811005263



http://link.springer.com/article/10.1007/s00704-007-0312-6











2.3.3 Cool Facades – Case Study


Experimental measurement of cool facades’ performance in a dense urban environment.- Street Canyon (La Rochelle France)

Cool Barrier Façade Dark Brown Color

The analysis and the measures of surface temperatures

have shown the physical similarities between the reduced-scale model and a real scale urban scene with street canyons.

After application of cool selective paint on street facades, reductions of surface temperatures up to 1.5 ◦C were observed compared to the reference street. Direct impacts on indoor air temperatures were also measured. The hotter periods (indoor air temperature) of modified buildings, compared to the reference building, were reduced by 10% (maximum indoor air temperature difference increased up to 2.5 ◦C).


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U.H.I Mitigation Project Athens*.1


ATHENS HEAT ISLAND EFFECT: Depiction of Existing Situation and

Proposals*

• Climate of Athens=hot summers

• Physical layout and Topography=

urban density and high buildings

• inappropriate materials and few

green open spaces

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*Author: A. Tsolaki Bioclimatic Architect

U.H.I Mitigation Project Athens.2


A 3 stage STUDY APPROACH Field Survey Summer Period

Microclimate Project

Evaluation of the proposals

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The measurements were made across all region in summer, between July and August 2007 All the parameters affecting the thermal regime in the region: were measured: • Ambient Temperature (Ta,ºC) • Relative Humidity (RH%) • Wind Speed WS (m/sec) • Surface Temperature (Ts, ºC)

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Surface Temperature (Ts, ºC)

PERIPHERIC, WIDE MAIN STREETS OPEN SPACES PAVEMENT MATERIALS GREEN AND WATER ELEMENTS BUILDINGS

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Grass temperature under shade: 26 ºC Road temperature under shade: 42 ºC Road temperature unshaded: 56 ºc

The green area has a lower surface temperature with 10 -20 degrees of difference.

The grass under shade presents about 10 degrees of difference from the grass unshaded.

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Microclimatic Parameters:

(Ta>32 ºC) - High temperatures

(WS<2.2m/sec) - Low wind speeds

(RH<35%) - Low relative humidity

Buildings: Remarks-Infrared Thermography

• Temperature range building’s facades,

ΔTsurf ~15.0ºC • Min mean daily Tsurf, 30.0ºC

white coatings • Max mean daily Tsurf , 45.0ºC

dark colored coatings

Streets, Pavements Remarks-Infrared Thermography • Min daily Tsurf, 29.9ºC

(for white marble) • Max daily Tsurf, 61.0ºC

(for dark grey concrete tiles)

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In the 90% of the measurements, the maximum air temperature (Ta ) in the region fluctuated well above 32ºC This is on average, the highest price for Athens during July and August.

The spatial variation of the air temperature is low. The atmosphere is a "capable mixer" that any change in temperature or moisture can be smooth out relatively quickly. The wind instead, is a microclimatic feature that can significantly influenced / changed from buildings or other forms/structures/profiles in the terrain

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For the period of measurements in Psyrri, the average value of the intensity of the wind ranged from 0.5 to 2.2 m / sec approx.

The low airspeed interpreted by the geometric characteristics of the narrow roads and due to the densely built area, which ultimately function as an urban canopy, resulting in bad air circulation within the region

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Thom’ Discomfort index, DI Cooling Power, CP Uncomfortably hot environment

The bioclimatic conditions, as they are represented by the discomfort index DI and the cooling power CP, result in thermal discomfort for the majority of the population.

More than half population feels discomfort

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CURRENT URBAN FORM •HISTORIC FAMOUS COMMERCIAL AREA

•SARRI STREET AS A MAIN BALANCE AXIS

•INHABITED BY THE LOW-INCOME PEOPLE

Land Use:

• Commercial 1

• Residential 2

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The main architecture is not really nice and most of the buildings are big blocks of cement dating from 1970, the time when a lot of people immigrated massively to Athens to find work. Many significant buildings are deteriorated and almost ready to be demolished.

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2 Techniques of microclimatic modifications:

Radiation modification:

Reduce solar radiation using shading techniques

Increase reflected radiation using light colors

Use cool materials with high reflectivity and emissivity

Temperature-Humidity modification:

•Protection of the area from the prevailing atmospheric systems with the use of tall walls, dense vegetation..etc

•Creation of water elements evaporation increase humidity reduction of air temperature

•Green planning (vegetation) increase evapotranspirationincrease humidity

•Vegetation for shade increase shading reduction of air temperature

Wind modification:

Characteristics of landscape elements modify wind speed and direction

Depending on:

i) Size of the study area

ii) Location of the area

iii) Orientation

iv) Porosity

v) Proximity

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1

Final PROPOSALS

•NEW PEDESTRIAN TRACKS

•INCREASE VEGETATION

•USE OF COOL MATERIALS

•SHADED OPEN SPACES

•WATER ELELEMENTS

•GREEN ROOFS

•LIGHT COLORS

•RENOVATION

•GREEN CARPETS PSIRRI : MICROCLIMATIC PROPOSALS

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PSIRI : FIELD MEASUREMENTS OF MICROCLIMATIC PARAMETERS

It is important to treat each space as an individual case.

Further research is required in order to evaluate all τhe suggested improvements through the CFD model simulation

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1

NEW PLAN : RENOVATE SIGNIFICANT BUILDINGS

Preservation and restoration of individual historic monuments and buildings with a significant architectural and environmental qualities

Preservation and restoration with cool materials for roofs and walls and the surrounding open space.

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1

Simulation Programs

Evaluation of proposed climate and architectural interventions to improve the microclimate performed with computational fluid dynamics CFD models:

o PHOENICS and o ENVI-MET

able to portray the physical and chemical processes in the atmosphere at various scales. - Small Scale= 2 mm – 1 km ! Using computer models provide valuable information especially for urban areas, where the flow of the wind, characteristics of turbulence and the meteorological factors (temperature, humidity, etc.) affected by the existence of buildings !!!

The purpose is to evaluate the wind flow field and temperature in the area, after the application of techniques to improve microclimate.

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1

Before

The maximum air temperature is: Ta = 31.2 ° C and occurs in most streets of the historic center with bright red color, while the minimum is: Ta = 30.2 ° C and it is noted in the archaeological site and to green spaces with green hues.

The results are plotted in the form of spatial distributions The color scale corresponds to a similar price range.

Air temperature

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1

Before Surface temperature

The difference of surface temperatures is Remarkable The minimum value Tc = 31.8 ° C noted in Liberty Square the maximum value Tc = 48.9 ° C Street Sarris

In terms of thermal comfort, the unfavorable climatic conditions, are primarily due to the lack of greenery and the use of conventional materials (under consideration in the simulations of the existed situation)

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1

Before Air Flow

The topography of the area is included in the simulation model in order to estimate the effect of building structures into air circulation. The height of buildings ranging from 7.5-22.0 m.

The low airspeed is interpreted by the geometric characteristics of the narrow winding streets, the dense structures and the relative orientation, which ultimately function as urban canopy. The result is bad air circulation within the region.

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Evaluation of proposals for improving the microclimate Comparing the results of the new and the current situation there is a significant

reduction in ambient temperature on average 2 ° C.

The improvement of the microclimatic characteristics it is worth mentioning: – Thermal comfort Improvement –Reduce of Energy consumption for cooling

There is a remarkable reduction of surface temperatures, after the application of the architectural interventions, of about 10 ° C on average.

Surface Temperature after the application of the proposed interventions

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Conclusions From all the above, it was confirmed that:

the use of new suitable reflective MATERIALS

the use of suitable VEGETATION

and the reduction of anthropogenic heat

Play a crucial role modifying significantly the microclimate and thus the thermal comfort conditions.

A comprehensive strategy to improve the microclimate in city scale requires an integrated scientific project where every intervention has been studied and evaluated. Empirical and partial interventions of local character, without comprehensive dimension, will have minimum contribution even if they are into the right direction.

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3.0 Water Effects of Urban Surfaces


Water evaporation from urban surfaces can also moderate

temperatures.

Evaporation from green roofs releases moisture into the air,

unlike hard surface rooftops.

Porous paving allows moisture to stay near the surface and cool by

evaporation, while storing less heat than conventional paving.

Many types of porous paving products are available, including this grass surface application on a sports arena parking lot.

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3.1 Green Roofs


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Green roofs place vegetation on a roof assembly that includes a drainage system with a growing medium for plants.

Green roofs cool by (1) shading the roof surface and (2) through moisture evaporation from soils and plants.

These roofs may be extensive systems, which are installed with a thin planting soil (4 to 6 inches), or intensive systems, with deeper soils and larger plants.

3.2 Porous Paving


Porous paver driveway

Porous paving has been used to replace conventional paving for improved stormwater management.

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There are many types of porous or pervious paving, including pervious concrete and porous asphalt.

These pavements cool by evaporation of water in the pavement, convective airflow, and reduced thermal storage.

They are primarily used for non-road surfaces, although they are capable of higher traffic loads.

Stormwater management and design features are key attributes for considering porous paving.

General Conclusions


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Urban heat islands occur due to the ways cities are built, as well as an area’s climatic conditions.

The effects are wide ranging, from higher energy costs to impacts on the quality of life.

Reducing heat island effects requires substantial changes to urban surfaces, including the amount and type of tree cover, roofing, and paved surfaces.

Reflective Materials Use Conclusions


The use of Reflective Materials in city scale (buildings and urban spaces) can effectively contribute into Urban Heat Island Consequences Mitigation:

Temperature and Smog reduction

Lower surface temperature increase thermal comfort conditions of the land users.

Lower air temperatures penetrate into the surrounding buildings – thermal comfort in buildings –energy savings

…and more

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Cool Barrier Materials: Global Warming 1


EFFECT OF COOL MATERIAL USE IN THE REDUCTION OF THE GLOBAL TEMPERATURE AND IN THE REDUCTION OF GREENHOUSES GASES EMITTANCE

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For the reduction of the climate - affecting greenhouse gases emissions, international community, European Union, and single countries have searched solutions through agreements, directives and rules (Kyoto Protocol, renewable energy and energy saving directives and incentives).

Another solution is to enhance the average Earth’s albedo increasing the solar energy which is reflected by the Earth.

Such energy doesn’t add to the Earth’s warming.

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• Proposed technology is to immediately reflect, as soon as it reaches the earth surface, a portion of the solar short wavelength radiation before it becomes long wavelength heat

• From in-depth scientific researches (CIRIAF National Congress March 2007 Ph Rossi et al) , pinpoint that a certified white reflecting surface of about 1 m2 with a reflection coefficient higher than 90-95%, can compensate in one year (depending on latitude and orientation of surfaces) the production 50-100 kg of equivalent carbon dioxide

www.albedocontrol.it/

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Using cool roofs and cool pavements in urban areas, on the average, can increase the albedo of the urban areas by 0.1.

We estimate that increasing the albedo of urban roofs and paved surfaces will induce a negative radiative forcing on the earth surface equivalent to removing 22 Gt CO2 from atmosphere.

Given these potential savings, we would like to recommend establishing an international organization where the developed countries offer financial support to large cities in developing countries, to trigger a cool roof/pavement program in those cities.

Hashem Akbari and Surabi Menon Lawrence Berkeley National Laboratory, USA [email protected] Arthur Rosenfeld California

Energy Commission, USA [email protected] 2006

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1

Cool Barrier Materials: Global Warming 5 57

Literature


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For the preparation of this presentation a lot of info and data were selected from the following addresses and authors:

http://www.epa.gov/heatisland/

http://heatisland.lbl.gov/

http://www.urbanheatislands.com/

http://eu-uhi.eu/

http://www.osti.gov/scitech/biblio/860475

http://www.albedocontrol.it/Pubblicazioni/ALBEDOSAT.pdf

http://www.aceee.org/research-report/u1405

http://www.whiteroofproject.org/urban-heat-islands

http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch3s3-2-2-2.html







http://eu-uhi.eu/

http://eu-uhi.eu/

http://eu-uhi.eu/

http://eu-uhi.eu/























We Can Make The World Cooler !

Thank You Very Much!


Technology

Abolin Co: Urban Heat Island - An Eye On Materials