What Is A Smart Surface?

Smart Surfaces include reflective (cool) roofs and pavements, porous and permeable pavements, green roofs, solar PV, trees, and combinations of these surfaces.

This page briefly overviews each surface technology, including how they work and the benefits they provide over conventional surfaces. For more information on calculating costs and benefits, see the pages and links provided beneath each surface’s description.

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Reflective (Cool) Roofs & PAVEMENTS

Graphic illustrating the difference between sunlight hitting a dark roof, which absorbs more light and transfers more heat into its surroundings, and a light, reflective roof, which transfers less heat into city air, the atmosphere, and the building. — Source: US DoE, Lawrence Berkeley National Lab

Cool roofs are light-colored and engineered to reflect most sunlight, reducing the heating of outdoor air. Traditional dark-colored roofs absorb more of the light that falls on them, radiating heat into the building and the surrounding air, which increases cooling costs and energy consumption while decreasing comfort.

Benefits of cool roofs:

Less heat emitted into outdoor air
- Lower energy costs
- Increased outdoor comfort
- Reduced pollution (slower formation of ground-level ozone)
Less heat transferred into building
- Lower energy costs (reduced demand for indoor cooling)
- Increased indoor comfort
- Reduced pollution (reduced demand on non-renewable power plants)
Other benefits, costs, and additional information on cool roofs can be found on pages 54-63 in Delivering Urban Resilience

The benefits and costs of cool pavements, including reduced pavement surface temperature and increased pavement lifespan, can be found on pages 87-100 of Delivering Urban Resilience.

Porous and permeable Pavements

Illustration of permeable pavement and other strategies of improving stormwater management on a street. — Source: Resilient Jacksonville and SCAPE Studio

Porous and permeable pavements allow rain to recharge groundwater, reducing water pollution, stormwater runoff, and flood risk. Pervious pavement technologies include porous concrete, permeable pavers, and porous grid pavers with turf or gravel. In addition to reducing flood risk and water pollution, porous pavements can lower temperatures through evaporative cooling.

Benefits of porous pavements:

Reduced stormwater runoff
- Lower flood risk
- Lower water treatment costs
Reduced water pollution
- Porous pavements and soil filter out stormwater pollutants
- Decreased likelihood of stormwater overflow into sewers and bodies of water in the 860 US municipalities with combined sewer systems (for more information, see the US EPA’s CSS web page)
Other benefits, costs, and information on porous pavements can be found on Soils Matter, Get the Scoop!

Green Roofs

Graphic comparing a green roof and a traditional roof. The green roof transfers less heat into its surroundings and retains more stormwater, while the traditional roof gives off more heat and is more likely to facilitate stormwater runoff. — Source: EPA Green Roof Case Study

Green roofs are living, breathing entities that absorb rainwater, reduce heat absorption, and improve air quality. They cool buildings, reduce stormwater runoff, and provide urban plant and wildlife habitats while maintaining longer effective lifespans than traditional dark and impervious roofs.

Benefits of green roofs:

Less heat transferred into building
- Reduced energy consumption and costs
- Increased comfort
Less heat transferred into outdoor air
- Increased outdoor comfort
Reduced pollution and GHGs into outdoor air
- Plants directly reduce CO2, NO2, and PM2.5
Reduced stormwater runoff
- Decreased water pollution, flood risk, and water treatment costs
Other benefits, costs, and additional information on green roofs can be found on pages 64-78 in Delivering Urban Resilience

Low- and Zero-Carbon Concrete

Concrete is currently responsible for about 8% of global emissions. Carbon-sequestering concrete offers an increasingly cost-effective pathway to cut concrete’s emissions footprint dramatically. With innovations to date, concrete can now be carbon-neutral or even carbon-negative. Low- and zero-carbon concrete also has a relatively high albedo. Innovation of the carbon-sequestering potential of cement is a core objective of the Smart Surfaces Coalition and SSC partner, the World Cement Association.

Benefits of low- and zero-carbon concrete:

Reduced carbon footprint of concrete
Relatively high albedo, cutting local temperatures and mitigating climate change via negative radiative forcing
More rigidity, increasing vehicle efficiency in hot conditions

Trees

Urban trees turn CO2 into oxygen, remove pollutants from the air, and reduce flood risk. Trees also reduce ambient temperature through shading and evapotranspiration, lowering reliance on energy-intensive air conditioning.

Benefits of trees:

Reduced temperature through shading and evapotranspiration
- Lower energy consumption for indoor cooling
- Increased comfort at the street level and in buildings
Decreased pollution
- Improved health outcomes from lower CO2 and ground-level ozone levels
- Reduced water pollution caused by runoff during heavy rains
Reduced flood risk
- Greater absorption of water during heavy rains

Other benefits, costs, and additional information on trees can be found on pages 101-110 in Delivering Urban Resilience

Solar PV

Solar PV converts sunlight into renewable energy and provides shading for buildings, sidewalks, and other public areas. Solar surfaces can help cities reduce their reliance on fossil fuels, cutting greenhouse gas emissions while reducing air pollution and energy costs.

Benefits of solar PV:

Decreased pollution
- Reduced energy demand on non-renewable power plants, thereby decreasing greenhouse gas emissions and improving air quality
Reduced energy costs
- Electricity produced by rooftop solar PV can be used in the building or sold back to the grid
- The levelized cost of energy for utility-scale solar PV is lower than for non-renewable sources
Other benefits, costs, and additional information on solar PV can be found on pages 79-86 in Delivering Urban Resilience

Bioretention (rain gardens & Bioswales)

Illustration of a street with a bioswale, street planting, and planted buffers along parking lots. — Source: Resilient Jacksonville and SCAPE Studio

Bioretention systems such as rain gardens or bioswales improve urban drainage by collecting and filtering stormwater runoff, promoting biodiversity, and adding aesthetic value. In addition, the vegetation in these systems cools the surrounding environment through evapotranspiration.

Benefits of bioretention:

Stormwater collection
- Reduced peak flow volumes in sewage systems during rain events, decreasing urban flood risk
- Recharged local groundwater stores
Pollutant filtration
- Reduced pollutant concentrations by filtering stormwater through soil, sand, or gravel mixtures
Habitat creation
- Opportunities for native plants and wildlife to thrive

Urban Meadows

People working in an urban meadow filled with grasses and wildflowers in Baltimore, MD. — Source: Wildflower project in Baltimore, Maryland

Urban meadows are planted areas of native grasses and herbaceous flowering plants that can take the spot of vacant lots and turfgrass lawns in urban areas. Hard-packed vacant lots are costly for cities to maintain and contribute to flooding and poor air quality. Turfgrass lawns require regular mowing and maintenance, are less effective at managing stormwater, and support less biodiversity than a thriving, diverse natural ecosystem. Urban meadows are a cost-effective strategy to reduce these challenges while providing significant community and aesthetic benefits.

Benefits of urban meadows:

Reduced maintenance costs in comparison with vacant lots and traditional landscaping
Improved stormwater management during rain events
Provision of valuable community green space

Combinations of Surfaces

By combining Smart Surface solutions, cities can maximize the benefits from a single area.

Cool roofs + bifacial solar PV allow more energy to be produced by the solar PV cells while also reflecting sunlight and heat away from the building and surrounding air.

Green roofs + solar PV generate clean energy, reduce building energy use, manage stormwater runoff, and filter air pollutants.

Porous + cool surfaces reflect heat, capture rainwater, and filter air pollutants.

Combination green and high albedo (reflective) roofs reduce air temperature in and around buildings, and help manage stormwater runoff.

Solar PV creates electricity from sunlight, reducing energy demand from sources that emit greenhouse gasses.

Porous, higher albedo pavers alongside streets absorb rain that runs off impervious pavement, reducing flood risk and water pollution.

Increased shading and evapotranspiration from trees cleans air and keeps sidewalks more comfortable for pedestrians, and can collectively cool entire urban areas.

Green, porous, and high-albedo parking lots reduce flood risk and absorb and emit much less heat than traditional dark, impervious asphalt parking lots.

Rain gardens allow rain to soak into the ground, reducing runoff.

Combination solar and high-albedo roofs cut urban heat while generating clean energy.

Trees provide shading and perform evapotranspiration, cooling and cleaning the air.

Sidewalk and street pavers are cooler and more porous than conventional dark, impervious pavements, reducing stormwater runoff and associated pollution and flooding risk.

Green, porous, and cool sidewalk pavers mitigate urban heat and flood risk.

Tree canopy provides shade to pedestrians and improves air quality by filtering out harmful air pollutants.

Sidewalk and street pavers that are more porous than traditional pavement reduce stormwater runoff and associated pollution and flooding risk.

Solar PV generates clean electricity from sunlight.