Hashem Akbari | Concordia University (Canada) (original) (raw)
Papers by Hashem Akbari
We have developed a hybrid method for adjusting the reconciled EUis to reflect the impacts of sta... more We have developed a hybrid method for adjusting the reconciled EUis to reflect the impacts of standards, changing energy prices, and changing technologies. The focus of our method is on HV AC end uses because they are the end uses most affected by standards and because they interact strongly with the non-HV AC end uses. Our methodology and the adjusted EUis by vintages are summarized in Chapter VIII.
Energy Reports, Nov 1, 2022
Building and Environment, Feb 1, 2022
Computational Urban Science, Aug 4, 2023
Cool materials and rooftop vegetation help achieve urban heating mitigation as they can reduce bu... more Cool materials and rooftop vegetation help achieve urban heating mitigation as they can reduce building cooling demands. This study assesses the cooling potential of different mitigation technologies using Weather Research and Forecasting (WRF)-taking case of a tropical coastal climate in the Kolkata Metropolitan Area. The model was validated using data from six meteorological sites. The cooling potential of eight mitigation scenarios was evaluated for: three cool roofs, four green roofs, and their combination (cool-city). The sensible heat, latent heat, heat storage, 2-m ambient temperature, surface temperature, air temperature, roof temperature, and urban canopy temperature was calculated. The effects on the urban boundary layer were also investigated. The different scenarios reduced the daytime temperature of various urban components, and the effect varied nearly linearly with increasing albedo and green roof fractions. For example, the maximum ambient temperature decreased by 3.6 °C, 0.9 °C, and 1.4 °C for a cool roof with 85% albedo, 100% rooftop vegetation, and their combination. The cost of different mitigation scenarios was assumed to depend on the construction options, location, and market prices. The potential for price per square meter and corresponding temperature decreased was related to one another. Recognizing the complex relationship between scenarios and construction options, the reduction in the maximum and minimum temperature across different cool and green roof cases were used for developing the cost estimates. This estimate thus attempted a summary of the price per degree of cooling for the different potential technologies. Higher green fraction, cool materials, and their combination generally reduced winds and enhanced buoyancy. The surface changes alter the lower atmospheric dynamics such as low-level vertical mixing and a shallower boundary layer and weakened horizontal convective rolls during afternoon hours. Although cool materials offer the highest temperature reductions, the cooling resulting from its combination and a green roof strategy could mitigate or reverse the summertime heat island effect. The results highlight the possibilities for heat mitigation and offer insight into the different strategies and costs for mitigating the urban heating and cooling demands.
In this study, sponsored by the California Energy Commission (CEC), we used a new end-use load sh... more In this study, sponsored by the California Energy Commission (CEC), we used a new end-use load shape estimation technique to develop a database of commercial sector end-use load shapes and energy-use intensities (EUIs) for the CEC's commercial energy and peak load forecasting models. The technique relied on a reconciliation of whole-building hourly electricity load data to energy simulations developed from
Building and Environment, Mar 1, 2023
The suitability of a pigment for inclusion in ''cool'' colored coatings with high solar reflectan... more The suitability of a pigment for inclusion in ''cool'' colored coatings with high solar reflectance can be determined from its solar spectral backscattering and absorption coefficients. Pigment characterization is performed by dispersing the pigment into a transparent film, then measuring spectral transmittance and reflectance. Measurements of the reflectance of film samples on black and white substrates are also used. A model for extracting the spectral backscattering coefficient S and absorption coefficient K from spectrometer measurements is presented. Interface reflectances complicate the model. The film's diffuse reflectance and transmittance measurements are used to determine S and K as functions of a wavelength-independent model parameter s that represents the ratio of forward to total scattering. s is used to estimate the rate at which incident collimated light becomes diffuse, and is determined by fitting the measured film reflectance backed by black. A typical value is s ¼ 0:8: Then, the measured film reflectance backed by white is compared with a
This paper summarizes the results of a simulation effort in support of ASHRAE SSPC 90.1 for the i... more This paper summarizes the results of a simulation effort in support of ASHRAE SSPC 90.1 for the inclusion of reflective roofs in the proposed standard. Simulation results include the annual electricity and fuel use for two buildings types, residential and nonresidential. The ...
Journal of Materials Science, Nov 1, 2006
This paper describes an ongoing project to demonstrate an affordable, safe, and energy-efficient ... more This paper describes an ongoing project to demonstrate an affordable, safe, and energy-efficient housing technology based on expanded polystyrene (EPS) panels with a cementitious coating. The concepts being described are (1) EPS panels embedded with galvanized steel trusses, steel mesh welded or clipped to the protruding points of the trusses and finished with a coating of cement plaster; (2) fiber-reinforced cement board panels and a core of EPS, glued together with high-strength adhesive, dried under high pressure, and connected with cellulose fiber cement board splines; and (3) EPS panels coated with a fiber-reinforced composite. The scope of this project is to model energy flows, analyze costs, simulate seismic forces, test against environmental conditions, and build pilot houses initially in California, Texas and Afghanistan. Results from air quality and energy flow analyses, preliminary cost modeling, structural calculations, and fire testing are reported. The performance goals address seismic safety; energy efficiency in extreme temperatures to reduce fuel use and indoor air quality hazards; affordability and simplicity of construction, as well as ease of expansion for future development; local employment opportunities and small-scale capital investments; and finally, cultural acceptance through education and adaptation to traditional architecture.
Atmospheric Environment, May 1, 2016
Abstract Increasing albedo is an effective strategy to mitigate urban air temperature in differen... more Abstract Increasing albedo is an effective strategy to mitigate urban air temperature in different climates. Using reflective urban surfaces decreases the air temperature, which potentially reduces the rate of generation of smog. However, for implementing the albedo enhancement, complicated interactions between air, moisture, aerosols, and other gaseous contaminant in the atmosphere should be considered. We used WRF-CHEM to investigate the effect of increasing albedo in Montreal, Canada, during a heat wave period (July 10th through July 12th, 2005) on air quality and urban climate. The reflectivity of roofs, walls, and roads are increased from 0.2 to 0.65, 0.6, and 0.45, respectively. Air temperature at 2-m elevation is decreased during all hours in the simulation period and the maximum reduction is about 1 °C on each day (T max is reduced by about 0.7 °C) The concentration of two regulated pollutants −ozone (O 3 ) and fine particulate matters (PM 2.5 ) − is calculated at a height of 5-m above the ground. The maximum decrease in 8-h averaged ozone concentration is about 3% (∼0.2 ppbv). 24-h averaged PM 2.5 concentration decreases by 1.8 μg/m 3 . This relatively small change in concentration of pollutants is related to the decrease in planetary boundary layer height caused by increasing the albedo. Additionally, the combined effect of decreased solar heat gain by building surfaces and decreased air temperature reduces the energy consumption of HVAC systems by 2% (∼0.1 W/m 2 ), which exacerbates the positive effect of the albedo enhancement on the air quality.
urban climate, Jun 1, 2018
The extreme effects of urban heat island (UHI) on energy consumption, air quality, and human heal... more The extreme effects of urban heat island (UHI) on energy consumption, air quality, and human health are significantly detrimental. Increasing the albedo of urban surfaces has been proposed as a potentially efficient mitigation strategy. In this study the Weather Research and Forecasting (WRF) mesoscale model has been used to simulate the urban climate of Rome (Italy).Four different scenarios have been analyzed: the Base Scenario as control case; the Base-ALB Scenario, in which the albedo of roof, walls and road have been increased; the Morph Scenario in which the morphology of urban area has been parameterized more accurately; the Morph-ALB Scenario in which the urban albedo of the improved model has been increased. This study demonstrates that a more accurate parametrization of the urban morphology leads to a more accurate representation of UHI phenomenon. The simulation results show that albedo increase leads to the decrease of the 2-m air temperature at daytime and at night-time. Albedo increase offers very promising results in terms of UHI mitigation, reducing the temperature in the urban area by up to 4°C at daytime and a little increased (up to 1°C) in some locations at night time, compared to the control cases.
Lawrence Berkeley National Laboratory, Feb 28, 2001
Urban fabric data are needed in order to estimate the impact of light-colored surfaces (roofs and... more Urban fabric data are needed in order to estimate the impact of light-colored surfaces (roofs and pavements) and urban vegetation (trees, grass, shrubs) on the meteorology and air quality of a city, and to design effective implementation programs. In this report, we discuss the result of a semi-automatic Monte-Carlo statistical approach used to develop data on surface-type distribution and city-fabric makeup (percentage of various surface-types) using aerial color orthophotography. The digital aerial photographs for Salt Lake City covered a total of about 34 km 2 (13 mi 2). At 0.50-m resolution, there were approximately 1.4 x 10 8 pixels of data. Four major land-use types were examined: 1) commercial, 2) industrial, 3) educational, and 4) residential. On average, for the areas studied, vegetation covers about 46% of the area (ranging 44-51%), roofs cover about 21% (ranging 15-24%), and paved surfaces about 26% (ranging 21-28%). For the most part, trees shade streets, parking lots, grass, and sidewalks. In most non-residential areas, paved surfaces cover 46-66% of the area. In residential areas, on average, paved surfaces cover about 32% of the area. Land-use/land-cover (LU/LC) data from the United States Geological Survey were used to extrapolate these results from neighborhood scales to metropolitan Salt Lake City. In an area of roughly 560 km 2 , defining most of metropolitan Salt Lake City, over 60% is residential. The total roof area is about 110 km 2 , and the total paved surface area (roads, parking areas, sidewalks) covers about 170 km 2. The total vegetated area covers about 230 km 2 .
Journal of Earth Science & Climatic Change, Sep 1, 2014
A s the threat of climate change becomes more pronounced, a number of scientists have proposed su... more A s the threat of climate change becomes more pronounced, a number of scientists have proposed supplementing the full range of mitigation efforts with geo-engineering (manipulation of the Earth's environment) to quickly respond to this threat. Many proposed geo-engineering techniques are novel and unproven. One simple technology has been in practice for thousands of years: changing the solar reflectance (albedo) of the built surface. "Cool roofs" and "cool pavements" should be among the first geo-engineering techniques used to combat global warming. Increasing the solar reflectance of the urban surface reduce its solar heat gain, lowers its temperatures, and decreases its outflow of thermal infrared radiation into the atmosphere. This process of "negative radioactive forcing" can help counter the effects of global warming. It is estimated that resurfacing conventional dark roofs with a cool white material that has a long-term solar reflectance of 0.60 or more increases its solar reflectance by at least 0.40. Retrofitting 100 m 2 of roof has an effect on radioactive forcing equivalent to a one-time offset of 10 tonnes of CO 2. Similarly, the solar reflectance of pavement can be raised on average by about 0.15, the equivalent of a 4 t reduction in CO 2 per 100 m 2. In addition, cool roofs reduce cooling-energy use in air conditioned buildings and increase comfort in unconditioned buildings; and cool roofs and cool pavements mitigate summer urban heat islands, improving outdoor air quality and comfort. Installing cool roofs and cool pavements in cities worldwide is a compelling win-win-win activity that can be undertaken immediately, outside of international negotiations to cap CO 2 emissions. The status of cool roof and cool pavements technologies, policies, and programs in the U.S., Europe, and Asia has been reviewed. An international campaign to use solar reflective materials when roofs and pavements are built or resurfaced in temperate and tropical regions is proposed. This paper will discuss the technologies and policies related to development and utilization of cool surface materials and their impact on energy use, urban climate change, and global climate change adaptation.
A {open_quotes}Cool Communities{close_quotes} strategy of lighter-colored reroofs and resurfaced ... more A {open_quotes}Cool Communities{close_quotes} strategy of lighter-colored reroofs and resurfaced pavements and shade trees can directly lower annual air conditioning bills in Los Angeles by {approximately}$$200M, cool the Basin by 3 C{degrees}, save indirectly 160M more in air conditioning, and reduce smog by {approximately}10%, worth another 360M,foratotalsavingsof360M, for a total savings of 360M,foratotalsavingsof$0.7B. To implement these savings, we call for ratings and labels for cool materials, building performance standards, utility programs, and an extension of the RECLAIM smog offset trading market to include credit for cool surfaces and trees. Generalized to the US, total annual savings will be {approximately}$$10B. Many more utilities can participate, and EPA (Environmental Protection Agency) can include cool materials and trees in its proposed regional {open_quotes}open market smog offset trading credits.{close_quotes}
urban climate, Dec 1, 2015
Abstract In this paper, effect of increasing the urban albedo in Montreal (Canada), a cold climat... more Abstract In this paper, effect of increasing the urban albedo in Montreal (Canada), a cold climate region, on 2-m air temperature and energy consumption of HVAC systems is investigated. An algorithm is developed to select “monthly typical meteorological days” that represent the weather of each month in 2005. The Weather Research and Forecasting (WRF) model is coupled with a multi-layer urban canopy model and a building energy model to accurately simulate the urban climate. The albedo of roof, walls, and road is increased from 0.2 to 0.65, 0.6, and 0.45, respectively. The simulated 2-m air temperature is decreased in all months and the maximum decrease in daily-averaged air temperature is occurred in April (∼0.4 °C). Air temperature decrease is mainly observed during the morning. The annual average decrease of the 2-m air temperature in the urban area is about 0.2 °C (0.2 °C in summer and 0.1 °C in winter). Increasing the albedo in Montreal decreased the air temperature during summertime by as high as 4 °C. Increasing urban albedo showed a small effect on net annual cooling and heating energy expenditure. With the simplified building energy model used in WRF, the annual energy expenditure savings is about 1 $/100 m2.
Materials for the New Millennium, 1996
Journal of Civil Engineering and Management, Dec 18, 2015
increase of the ambient air temperature in cities caused by the urban heat island phenomenon has ... more increase of the ambient air temperature in cities caused by the urban heat island phenomenon has a serious impact on the economic and social system of cities. to counterbalance the consequences of the increased urban temperatures important research has been carried out resulting in the development of efficient mitigation technologies. the present paper aims to present the state of the art in terms of local climate change and urban heat island mitigation techniques. In particular, developments in the field on highly reflective materials, cool and green roofs, cool pavements, urban green and of other mitigation technologies are presented in detail, while examples of implemented projects are given.
![Research paper thumbnail of Erratum to “Solar spectral optical properties of pigments—Part I: Model for deriving scattering and absorption coefficients from transmittance and reflectance measurements” [Sol. Mater. Sol. Cells (2005) 89(4) 319–349]](https://attachments.academia-assets.com/112429602/thumbnails/1.jpg)
](Solar Energy Materials and Solar Cells, Dec 1, 2012
Energy and Buildings, Dec 1, 2017
HIGHLIGHTS The thermal behavior of an external opaque building element depends on several perfo... more HIGHLIGHTS The thermal behavior of an external opaque building element depends on several performance parameters. Commonly considered parameters related to insulation cannot describe the element behavior when it is subjected to the solar cycle. Parameters related to thermal inertia do not include the capability of reflecting solar energy toward the atmosphere. External radiative properties are unrelated to both insulation and inertia. The "solar transmittance index" (STI) takes into account both the radiative properties of the external surface and the thermo-physical properties of the materials under the surface ABSTRACT The thermal behavior of an external opaque building element depends on the combination of several physical characteristics related to insulation level, thermal inertia, external radiative properties. Concerning the insulation level, parameters like the R-value and its inverse, the U-value or thermal transmittance, are commonly considered in building codes, but they are defined with reference to steady-state conditions and cannot describe the behavior of the element when it is subjected to the cycle of solar radiation. On the other hand, parameters like periodic thermal transmittance, decrement factor and time shift represent the dynamic response of the element resulting from its thermal inertia, so they are often considered but do not include the capability of returning solar energy to the atmosphere. In this regard, a few additional parameters are relevant such as solar reflectance and thermal emittance of the external surface, which are unrelated to both insulation and inertia. In order to rate the overall dynamic behavior of an external opaque building element subjected to the cycle of solar radiation and constant indoor temperature, a "solar transmittance index" (STI) is proposed. STI includes in a single performance parameters the effects of both the radiative properties of the external surface and the thermo-physical properties of the materials under the surface. The utilization of such single performance parameter may be greatly helpful in defining requirements and policies to prevent building overheating, reduce cooling energy demand and mitigate the fallouts of the urban heat island effect.
We have developed a hybrid method for adjusting the reconciled EUis to reflect the impacts of sta... more We have developed a hybrid method for adjusting the reconciled EUis to reflect the impacts of standards, changing energy prices, and changing technologies. The focus of our method is on HV AC end uses because they are the end uses most affected by standards and because they interact strongly with the non-HV AC end uses. Our methodology and the adjusted EUis by vintages are summarized in Chapter VIII.
Energy Reports, Nov 1, 2022
Building and Environment, Feb 1, 2022
Computational Urban Science, Aug 4, 2023
Cool materials and rooftop vegetation help achieve urban heating mitigation as they can reduce bu... more Cool materials and rooftop vegetation help achieve urban heating mitigation as they can reduce building cooling demands. This study assesses the cooling potential of different mitigation technologies using Weather Research and Forecasting (WRF)-taking case of a tropical coastal climate in the Kolkata Metropolitan Area. The model was validated using data from six meteorological sites. The cooling potential of eight mitigation scenarios was evaluated for: three cool roofs, four green roofs, and their combination (cool-city). The sensible heat, latent heat, heat storage, 2-m ambient temperature, surface temperature, air temperature, roof temperature, and urban canopy temperature was calculated. The effects on the urban boundary layer were also investigated. The different scenarios reduced the daytime temperature of various urban components, and the effect varied nearly linearly with increasing albedo and green roof fractions. For example, the maximum ambient temperature decreased by 3.6 °C, 0.9 °C, and 1.4 °C for a cool roof with 85% albedo, 100% rooftop vegetation, and their combination. The cost of different mitigation scenarios was assumed to depend on the construction options, location, and market prices. The potential for price per square meter and corresponding temperature decreased was related to one another. Recognizing the complex relationship between scenarios and construction options, the reduction in the maximum and minimum temperature across different cool and green roof cases were used for developing the cost estimates. This estimate thus attempted a summary of the price per degree of cooling for the different potential technologies. Higher green fraction, cool materials, and their combination generally reduced winds and enhanced buoyancy. The surface changes alter the lower atmospheric dynamics such as low-level vertical mixing and a shallower boundary layer and weakened horizontal convective rolls during afternoon hours. Although cool materials offer the highest temperature reductions, the cooling resulting from its combination and a green roof strategy could mitigate or reverse the summertime heat island effect. The results highlight the possibilities for heat mitigation and offer insight into the different strategies and costs for mitigating the urban heating and cooling demands.
In this study, sponsored by the California Energy Commission (CEC), we used a new end-use load sh... more In this study, sponsored by the California Energy Commission (CEC), we used a new end-use load shape estimation technique to develop a database of commercial sector end-use load shapes and energy-use intensities (EUIs) for the CEC's commercial energy and peak load forecasting models. The technique relied on a reconciliation of whole-building hourly electricity load data to energy simulations developed from
Building and Environment, Mar 1, 2023
The suitability of a pigment for inclusion in ''cool'' colored coatings with high solar reflectan... more The suitability of a pigment for inclusion in ''cool'' colored coatings with high solar reflectance can be determined from its solar spectral backscattering and absorption coefficients. Pigment characterization is performed by dispersing the pigment into a transparent film, then measuring spectral transmittance and reflectance. Measurements of the reflectance of film samples on black and white substrates are also used. A model for extracting the spectral backscattering coefficient S and absorption coefficient K from spectrometer measurements is presented. Interface reflectances complicate the model. The film's diffuse reflectance and transmittance measurements are used to determine S and K as functions of a wavelength-independent model parameter s that represents the ratio of forward to total scattering. s is used to estimate the rate at which incident collimated light becomes diffuse, and is determined by fitting the measured film reflectance backed by black. A typical value is s ¼ 0:8: Then, the measured film reflectance backed by white is compared with a
This paper summarizes the results of a simulation effort in support of ASHRAE SSPC 90.1 for the i... more This paper summarizes the results of a simulation effort in support of ASHRAE SSPC 90.1 for the inclusion of reflective roofs in the proposed standard. Simulation results include the annual electricity and fuel use for two buildings types, residential and nonresidential. The ...
Journal of Materials Science, Nov 1, 2006
This paper describes an ongoing project to demonstrate an affordable, safe, and energy-efficient ... more This paper describes an ongoing project to demonstrate an affordable, safe, and energy-efficient housing technology based on expanded polystyrene (EPS) panels with a cementitious coating. The concepts being described are (1) EPS panels embedded with galvanized steel trusses, steel mesh welded or clipped to the protruding points of the trusses and finished with a coating of cement plaster; (2) fiber-reinforced cement board panels and a core of EPS, glued together with high-strength adhesive, dried under high pressure, and connected with cellulose fiber cement board splines; and (3) EPS panels coated with a fiber-reinforced composite. The scope of this project is to model energy flows, analyze costs, simulate seismic forces, test against environmental conditions, and build pilot houses initially in California, Texas and Afghanistan. Results from air quality and energy flow analyses, preliminary cost modeling, structural calculations, and fire testing are reported. The performance goals address seismic safety; energy efficiency in extreme temperatures to reduce fuel use and indoor air quality hazards; affordability and simplicity of construction, as well as ease of expansion for future development; local employment opportunities and small-scale capital investments; and finally, cultural acceptance through education and adaptation to traditional architecture.
Atmospheric Environment, May 1, 2016
Abstract Increasing albedo is an effective strategy to mitigate urban air temperature in differen... more Abstract Increasing albedo is an effective strategy to mitigate urban air temperature in different climates. Using reflective urban surfaces decreases the air temperature, which potentially reduces the rate of generation of smog. However, for implementing the albedo enhancement, complicated interactions between air, moisture, aerosols, and other gaseous contaminant in the atmosphere should be considered. We used WRF-CHEM to investigate the effect of increasing albedo in Montreal, Canada, during a heat wave period (July 10th through July 12th, 2005) on air quality and urban climate. The reflectivity of roofs, walls, and roads are increased from 0.2 to 0.65, 0.6, and 0.45, respectively. Air temperature at 2-m elevation is decreased during all hours in the simulation period and the maximum reduction is about 1 °C on each day (T max is reduced by about 0.7 °C) The concentration of two regulated pollutants −ozone (O 3 ) and fine particulate matters (PM 2.5 ) − is calculated at a height of 5-m above the ground. The maximum decrease in 8-h averaged ozone concentration is about 3% (∼0.2 ppbv). 24-h averaged PM 2.5 concentration decreases by 1.8 μg/m 3 . This relatively small change in concentration of pollutants is related to the decrease in planetary boundary layer height caused by increasing the albedo. Additionally, the combined effect of decreased solar heat gain by building surfaces and decreased air temperature reduces the energy consumption of HVAC systems by 2% (∼0.1 W/m 2 ), which exacerbates the positive effect of the albedo enhancement on the air quality.
urban climate, Jun 1, 2018
The extreme effects of urban heat island (UHI) on energy consumption, air quality, and human heal... more The extreme effects of urban heat island (UHI) on energy consumption, air quality, and human health are significantly detrimental. Increasing the albedo of urban surfaces has been proposed as a potentially efficient mitigation strategy. In this study the Weather Research and Forecasting (WRF) mesoscale model has been used to simulate the urban climate of Rome (Italy).Four different scenarios have been analyzed: the Base Scenario as control case; the Base-ALB Scenario, in which the albedo of roof, walls and road have been increased; the Morph Scenario in which the morphology of urban area has been parameterized more accurately; the Morph-ALB Scenario in which the urban albedo of the improved model has been increased. This study demonstrates that a more accurate parametrization of the urban morphology leads to a more accurate representation of UHI phenomenon. The simulation results show that albedo increase leads to the decrease of the 2-m air temperature at daytime and at night-time. Albedo increase offers very promising results in terms of UHI mitigation, reducing the temperature in the urban area by up to 4°C at daytime and a little increased (up to 1°C) in some locations at night time, compared to the control cases.
Lawrence Berkeley National Laboratory, Feb 28, 2001
Urban fabric data are needed in order to estimate the impact of light-colored surfaces (roofs and... more Urban fabric data are needed in order to estimate the impact of light-colored surfaces (roofs and pavements) and urban vegetation (trees, grass, shrubs) on the meteorology and air quality of a city, and to design effective implementation programs. In this report, we discuss the result of a semi-automatic Monte-Carlo statistical approach used to develop data on surface-type distribution and city-fabric makeup (percentage of various surface-types) using aerial color orthophotography. The digital aerial photographs for Salt Lake City covered a total of about 34 km 2 (13 mi 2). At 0.50-m resolution, there were approximately 1.4 x 10 8 pixels of data. Four major land-use types were examined: 1) commercial, 2) industrial, 3) educational, and 4) residential. On average, for the areas studied, vegetation covers about 46% of the area (ranging 44-51%), roofs cover about 21% (ranging 15-24%), and paved surfaces about 26% (ranging 21-28%). For the most part, trees shade streets, parking lots, grass, and sidewalks. In most non-residential areas, paved surfaces cover 46-66% of the area. In residential areas, on average, paved surfaces cover about 32% of the area. Land-use/land-cover (LU/LC) data from the United States Geological Survey were used to extrapolate these results from neighborhood scales to metropolitan Salt Lake City. In an area of roughly 560 km 2 , defining most of metropolitan Salt Lake City, over 60% is residential. The total roof area is about 110 km 2 , and the total paved surface area (roads, parking areas, sidewalks) covers about 170 km 2. The total vegetated area covers about 230 km 2 .
Journal of Earth Science & Climatic Change, Sep 1, 2014
A s the threat of climate change becomes more pronounced, a number of scientists have proposed su... more A s the threat of climate change becomes more pronounced, a number of scientists have proposed supplementing the full range of mitigation efforts with geo-engineering (manipulation of the Earth's environment) to quickly respond to this threat. Many proposed geo-engineering techniques are novel and unproven. One simple technology has been in practice for thousands of years: changing the solar reflectance (albedo) of the built surface. "Cool roofs" and "cool pavements" should be among the first geo-engineering techniques used to combat global warming. Increasing the solar reflectance of the urban surface reduce its solar heat gain, lowers its temperatures, and decreases its outflow of thermal infrared radiation into the atmosphere. This process of "negative radioactive forcing" can help counter the effects of global warming. It is estimated that resurfacing conventional dark roofs with a cool white material that has a long-term solar reflectance of 0.60 or more increases its solar reflectance by at least 0.40. Retrofitting 100 m 2 of roof has an effect on radioactive forcing equivalent to a one-time offset of 10 tonnes of CO 2. Similarly, the solar reflectance of pavement can be raised on average by about 0.15, the equivalent of a 4 t reduction in CO 2 per 100 m 2. In addition, cool roofs reduce cooling-energy use in air conditioned buildings and increase comfort in unconditioned buildings; and cool roofs and cool pavements mitigate summer urban heat islands, improving outdoor air quality and comfort. Installing cool roofs and cool pavements in cities worldwide is a compelling win-win-win activity that can be undertaken immediately, outside of international negotiations to cap CO 2 emissions. The status of cool roof and cool pavements technologies, policies, and programs in the U.S., Europe, and Asia has been reviewed. An international campaign to use solar reflective materials when roofs and pavements are built or resurfaced in temperate and tropical regions is proposed. This paper will discuss the technologies and policies related to development and utilization of cool surface materials and their impact on energy use, urban climate change, and global climate change adaptation.
A {open_quotes}Cool Communities{close_quotes} strategy of lighter-colored reroofs and resurfaced ... more A {open_quotes}Cool Communities{close_quotes} strategy of lighter-colored reroofs and resurfaced pavements and shade trees can directly lower annual air conditioning bills in Los Angeles by {approximately}$$200M, cool the Basin by 3 C{degrees}, save indirectly 160M more in air conditioning, and reduce smog by {approximately}10%, worth another 360M,foratotalsavingsof360M, for a total savings of 360M,foratotalsavingsof$0.7B. To implement these savings, we call for ratings and labels for cool materials, building performance standards, utility programs, and an extension of the RECLAIM smog offset trading market to include credit for cool surfaces and trees. Generalized to the US, total annual savings will be {approximately}$$10B. Many more utilities can participate, and EPA (Environmental Protection Agency) can include cool materials and trees in its proposed regional {open_quotes}open market smog offset trading credits.{close_quotes}
urban climate, Dec 1, 2015
Abstract In this paper, effect of increasing the urban albedo in Montreal (Canada), a cold climat... more Abstract In this paper, effect of increasing the urban albedo in Montreal (Canada), a cold climate region, on 2-m air temperature and energy consumption of HVAC systems is investigated. An algorithm is developed to select “monthly typical meteorological days” that represent the weather of each month in 2005. The Weather Research and Forecasting (WRF) model is coupled with a multi-layer urban canopy model and a building energy model to accurately simulate the urban climate. The albedo of roof, walls, and road is increased from 0.2 to 0.65, 0.6, and 0.45, respectively. The simulated 2-m air temperature is decreased in all months and the maximum decrease in daily-averaged air temperature is occurred in April (∼0.4 °C). Air temperature decrease is mainly observed during the morning. The annual average decrease of the 2-m air temperature in the urban area is about 0.2 °C (0.2 °C in summer and 0.1 °C in winter). Increasing the albedo in Montreal decreased the air temperature during summertime by as high as 4 °C. Increasing urban albedo showed a small effect on net annual cooling and heating energy expenditure. With the simplified building energy model used in WRF, the annual energy expenditure savings is about 1 $/100 m2.
Materials for the New Millennium, 1996
Journal of Civil Engineering and Management, Dec 18, 2015
increase of the ambient air temperature in cities caused by the urban heat island phenomenon has ... more increase of the ambient air temperature in cities caused by the urban heat island phenomenon has a serious impact on the economic and social system of cities. to counterbalance the consequences of the increased urban temperatures important research has been carried out resulting in the development of efficient mitigation technologies. the present paper aims to present the state of the art in terms of local climate change and urban heat island mitigation techniques. In particular, developments in the field on highly reflective materials, cool and green roofs, cool pavements, urban green and of other mitigation technologies are presented in detail, while examples of implemented projects are given.
Solar Energy Materials and Solar Cells, Dec 1, 2012
Energy and Buildings, Dec 1, 2017
HIGHLIGHTS The thermal behavior of an external opaque building element depends on several perfo... more HIGHLIGHTS The thermal behavior of an external opaque building element depends on several performance parameters. Commonly considered parameters related to insulation cannot describe the element behavior when it is subjected to the solar cycle. Parameters related to thermal inertia do not include the capability of reflecting solar energy toward the atmosphere. External radiative properties are unrelated to both insulation and inertia. The "solar transmittance index" (STI) takes into account both the radiative properties of the external surface and the thermo-physical properties of the materials under the surface ABSTRACT The thermal behavior of an external opaque building element depends on the combination of several physical characteristics related to insulation level, thermal inertia, external radiative properties. Concerning the insulation level, parameters like the R-value and its inverse, the U-value or thermal transmittance, are commonly considered in building codes, but they are defined with reference to steady-state conditions and cannot describe the behavior of the element when it is subjected to the cycle of solar radiation. On the other hand, parameters like periodic thermal transmittance, decrement factor and time shift represent the dynamic response of the element resulting from its thermal inertia, so they are often considered but do not include the capability of returning solar energy to the atmosphere. In this regard, a few additional parameters are relevant such as solar reflectance and thermal emittance of the external surface, which are unrelated to both insulation and inertia. In order to rate the overall dynamic behavior of an external opaque building element subjected to the cycle of solar radiation and constant indoor temperature, a "solar transmittance index" (STI) is proposed. STI includes in a single performance parameters the effects of both the radiative properties of the external surface and the thermo-physical properties of the materials under the surface. The utilization of such single performance parameter may be greatly helpful in defining requirements and policies to prevent building overheating, reduce cooling energy demand and mitigate the fallouts of the urban heat island effect.