historic buildings uhi and facade protection

Urban Heat Islands & Energy Restoration HISTORIC BUILDINGS

UHI, BASIC DESCRIPTION, IMPACTS AND MITIGATION TECHNOLOGIES

www.abolinco.com

Historic Building’s Façades Available Functional Painting Materials Technologies and Benefits

P.Perdikis

Basic Description

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.

Maps for the retrieved Land Surface Temperatures (LST) for Tanta city and outskirts. The images reveal the distribution of temperature values among the Nile Delta cultivated lands, the core of the city, outskirts, villages and hamlets.

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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

Cool Roof in Athens

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 11

Urban Canyon

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

Urban Canyon 12

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? 13

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.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 48

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 50

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

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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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HISTORIC BUILDINGS

Historic Structures are Inherently Sustainable

Historic Structures were traditionally designed with many sustainable features that responded to climate and site.

ANCIENT THEATRE IN EPIDAUROS

Buildings belonging to the cultural heritage are valuable assets and must be preserved for future generations. Therefore it is important that damaging temperature or humidity conditions caused by inappropriate construction measures are avoided.

Taking into account historic buildings' original climatic adaptations, today's sustainable technology can supplement inherent sustainable features without compromising unique historic character.

Taking into account historic buildings'

There are Standards for four distinct, but interrelated, approaches to the treatment of historic properties--preservation, rehabilitation, restoration, and reconstruction: • preservation, • rehabilitation, • restoration and • reconstruction. LEED-EB® SYSTEM

www.usgbc.org

36 CFR Part 67 US Std.

LEED 1.

http://www.usgbc.org/Store/CompanyRegistration.aspx?CMSPageID=1530

Preservation focuses on the maintenance and repair of existing historic materials and retention of a property's form as it has evolved over time. (Protection and Stabilization have now been consolidated under this treatment). Rehabilitation acknowledges the need to alter or add to a historic property to meet continuing or changing uses while retaining the property's historic character. Restoration depicts a property at a particular period of time in its history, while removing evidence of other periods. Reconstruction re-creates vanished or non-surviving portions of a property for interpretive purposes.

LEED 2.

Special attention: 1) Sustainable Sites - Heat Island Reduction

2) Water Efficiency - Water Use Reduction

3) Energy and Atmosphere – Energy Use Reduction

4) Materials and Resources - Use of natural materials from the near site, use of existed damaged

materials from the building, - Environmental and Sustainable criteria for new materials

5) Indoor Environmental Quality - Ventilation, Outdoor Air Quality, Sick Building Syndrome - Lighting and Daylighting

LEED 3.

Building Envelope Chapter 25 “Heat, Air, and Moisture Control in Building

Assemblies – Fundamentals” Chapter 26 “Heat, Air, and Moisture Control in Building

Assemblies – Material Properties” Chapter 27 “Heat, Air, and Moisture Control in Building

Assemblies – Examples”

Heat, Air, and Moisture Control 1. ASHRAE 2009 Fundamentals

http://connection.ebscohost.com/c/book-chapters/44410743/chapter-25-heat-air-moisture-control-building-assemblies-fundamentals

Chapter 25 “Heat, Air, and Moisture Control in Building Assemblies – Fundamentals” Hydrothermal loads acting

on building envelope

ASHRAE 2009 Handbook of Fundamentals


Chapter 25 “Heat, Air, and Moisture Control in Building Assemblies – Fundamentals” Hydrothermal loads acting

on building envelope



Chapter 25 “Heat, Air, and Moisture Control in Building Assemblies – Fundamentals” Hydrothermal loads acting on building envelope

Ambient Thermal Humidity Solar Radiation Exterior Condensation Wind-Driven Rain Construction Moisture Ground and Surface Water Air Pressure Differentials


Chapter 25 “Heat, Air, and Moisture Control in Building Assemblies – Fundamentals” Heat transfer

Steady-State Thermal Response Thermal Resistance of a Flat Assembly Combined Convective and Radiative Surface Transfer Heat Flow Across an Air Space Total Thermal Resistance of a Flat Building Assembly Thermal Transmittance of a Flat Building Assembly Thermal Bridging and Whole-Assembly Thermal

Transmittance Transient Thermal Response


Chapter 25 “Heat, Air, and Moisture Control in Building Assemblies – Fundamentals” Airflow

Water Vapor Flow by Air Movement Heat Flux with Airflow

Moisture Transfer Moisture Storage in Building Materials Moisture Flow Mechanisms Water Vapor Flow by Diffusion Water Flow by Capillary Suction Liquid Flow at Low Moisture Content Transient Moisture Flow


Chapter 25 “Heat, Air, and Moisture Control in Building Assemblies – Fundamentals” Moisture Transfer



Chapter 25 “Heat, Air, and Moisture Control in Building Assemblies – Fundamentals” Combined Heat, Air, And Moisture Transfer

Consequences of combined heat, air, and moisture transfer can be detrimental to a building’s thermal performance, occupant comfort, and indoor air quality.

High moisture levels in building materials may also have a negative effect on the thermal performance of the building envelope.

It is advisable to analyze the combined heat, air, and moisture transfer through building assemblies.


Restoration of buildings Why this increasing of the restoration in our cities? Mature societal claims

Promotion from the Government or

Town halls. Target: Conservation of historical city centers

Subsidies to the owners of the historical buildings to be restored

Restoration of Historical Centers

General rules for the retrofitting of historic buildings 1. Retain appearance of the building 2. Ensure reversibility 3. Without affecting the properties of the building/building envelope

Restoration of Historical Buildings

An Eye on the Restoration of Façades 1.

The requirements for wall performance were outlined some half a century ago (Hutcheon 1963)iii, and are applicable to all enclosure systems and components. The major considerations were identified as: Strength and rigidity Control of heat flow Control of air flow Control of water vapor flow Control of liquid water movement Stability and durability of materials Fire Aesthetic considerations Cost


Connection between the building and the city (and citizens)

Requirements :

- Aesthetic - Durability, - transpirability,

waterproofing, isolation, …

Façades

• Water degrading effect • Restoration process • Heat Stress • Künzel’s theory • Suggested Paints


Degradation Which is the major degrading agent for the building materials of the façade?

Water Water

Penetration

Capillarity

Pouring Rain

Condensation by Cooling

Capillary Condensation

Hygroscopic Absorption

DIRECT action by: Erosion / solubilization Softening of materials

Expansivity in case of frost Osmosis

Part 1

Water INDIRECT action by: Carrying with it salts: surface crystallization as white efflorescence, crusts, and degradation of the materials by crystallization inside.

Sulphates MgSO4.7H2O Magnesium sulphate, amaro salt CaSO4.2H2O Calcium sulphate, gypsum Na2SO4.10H2O Sodium sulphate, Glauber salt 3CaO.Al2O3.3CaSO4.32H2O Ettringite

Nitrates Mg(NO3)2.6H2O Magnesium nitrate Ca(NO3)2.4H2O Calcium nitrate 5Ca(NO3)2.4NH4NO3.10H2O Calcium and ammonium nitrate

Part 2


Part 3

Water INDIRECT action by: Carrying with it salts: surface crystallization as white efflorescence, crusts, and degradation of the materials by crystallization inside.

Chlorides CaCl2.6H2O Calcium chloride NaCl Sodium chloride Carbonates Na2CO3.10 H2O Sodium carbonate K2CO3 Potassium carbonate CaCO3 Calcium carbonate, calcite Ca(HCO3)2 Calcium bicarbonate


Water INDIRECT action by: Favouring sprouting and development of vegetation, bacteria, microorganisms, Mildews, fungi, lichens and insects.

Part 4

Reasons: Existence of nutrients

in the wall Water Organic polymer

of the coatings pH close to 7


Part 5

Insulating power of the wall

Presence of WATER


Decreases the insulating power of the wall (1/Λ Thermic insulation coefficient)

20% moisture in a cement plaster

HALVES the insulating power of the plaster

Part 5


HEAT STRESS Decreases the insulating power of the wall

Problems related to the integrity of building's elements, such as: • discolorations, cracks, expansions, contractionσ or shrinkage, blistering, ridging, splitting, and surface erosion

Urban pollution changes the aesthetic value of the building, decreases the durability of the materials, influences the intensity of the whole construction

Related Problems:

Künzel Theory

w (water absorption coefficient) < 0,5 kg/m2h0,5

Sd (resistance to vapour diffusion) < 2 m

Or w·Sd < 0,1 kg/mh0,5 w

kg/m2h0,5 Sd m

w Sd kg/mh0,5

Künzel theory < 0,5 < 2 < 0,1 Emulsion paints Emulsion plasters Pure silicate paints Silicate emulsion paints Hydrophobic ActivSil

≈ 0,25 ≈ 0,15 > 0,5 < 0,5

<< 0,5

> 1 > 1,5 < 0,05 < 0,05 < 0,05

> 0,2 > 0,2 ≈ 0,02 ≈ 0,02 ≈ 0,01

Paint System Performances Part 1

High permeability to the water vapour

The water vapour diffusion current density indicates how many grams of water vapour can diffuse per square meter area in one day through a paint layer. This can be calculated from the Sd value

Part 2

Long life (petrification / silicification) = Chemical reactions

A.- With the material of the wall

Reaction with sand (rough surfaces) Reaction with lime (calcium hydroxide):

B.- With the CO2 of the atmosphere

Total Silicification (Result: insoluble silica gel)

RESULT: Insoluble solid of inorganic/mineral nature composed of: SiO2, inorganic pigments, insoluble silicates of Ca, Al,..

Paint System Performances

Part 3

Low water absorption

Capillarity refers to the absorption/ desorption of water as liquid. Capillarity is a function of pore structure. It can be altered by coatings and additives and many of these act as hydrophobic agents by blocking these larger pores, but still allowing the smaller pores to remain open. In this way the pore structure may be kept open for hygroscopic and vapour permeable transfer of moisture but closed to capillary transfer of moisture. Capillarity is measured by placing a standard cube of material in water, with all sides sealed except the bottom. The weight of the material is then measured from time to time and this is expressed as a Co - efficient w kg/m2h0.5 Hydrophobic Action !


Part 4

High UV resistance Colorants obtained from special metallic oxides resistant to UV radiation.

Real Binder (silica) is high resistant to UV


Part 5

Biocide effect against development of algae, mildews, lichens,…

High pH (12) With this pH value is not possible the development of this type of microorganisms


Part 6

Maintenance of the aspect

Low tendency to the dirt pickup Particles of dust are not trapped by the paint Auto-washability Slow chalking effect. Rain removes some microns of the surface


Part 7

Naturally’ looking matt surface appearance / Maintenance of the morphology of the surface

NEVER gloss


Part 7a

Energy Savings Performance

The creation of surfaces of high reflectivity and emissivity in the urban environment constitutes an easily applicable and economic passive cooling method that contributes in the reduction of urban temperatures. The creation of such surfaces can be achieved with the use of “cool” materials which are characterized from :

- High solar reflectance

- High infrared emittance incident sunlight I

reflected sunlight Rsol × I

net emitted thermal radiation E × σ (T4 - Tsky

4)

opaque surface at temperature T

convection

conduction


Energy Savings Performance – Application onto Exterior Walls Optical Properties – Solar Reflectance, Infrared Emittance

a/a Coating Code

Color SR SR_NIR

(700-2500nm)

Infrared emittance

(error 0.02)

1 ActivSil White WHITE 0.90 0.93 0.89

2 ActivSil CB 013

LIGHT BLUE 0.82 0.87 0.90

3 ActivSil CB 015 LIGHT RED 0.78 0.89 0.89

4 ActivSil CB 016

LIGHT GREEN 0.81 0.87 0.89

5 ActivSil CB 022

LIGHT GREY 0.76 0.84 0.90

6 ActivSil CB 019

LIGHT OCHRE 0.85 0.91 0.88

Part 7b

The use on Buildings envelope drive to cooling needs reduction.

Less energy used, less CO2 emissions, lower electricity bills


Reasons to use this type of paint in buildings

ACTIVSIL Part 7c

• Cooling load reduction - Less heat penetrates into building

• Energy Savings - Minimize the need for cooling

• Money savings • Improved thermal comfort conditions • Improved public health conditions • Enhanced building’s durability - Less

thermal stress • Improved microclimatic conditions -

Urban Heat Island Mitigation

Energy Savings Performance – Application onto Exterior Walls Benefits from the use

Part 8

Air Purification and Smog Reduction

Can be formulated to perform photocatalytic action against: Nitrogen Dioxide Ozon Benzene Formaledeheyde Toluene Bacteria


ActivSil Technology

Literature 95

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://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

historic buildings uhi and facade protection

Engineering