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Cool Pavement Project

The City of Davis began its first Cool Pavement Demonstration Project on the Olive Drive Parking Lot (located at the NW corner of Richards Blvd and Olive Drive), on Monday, May 23 and Tuesday, May 24, 2022. This demonstration project is piloting a potential long-term design solution. The asphalt surface of the parking lot was coated with a "cool" pavement coating, a protective barrier that seals cracks and extends the life of the pavement and is solar reflective, designed to keep the street significantly cooler. The coating vendor, GAF, has agreed to donate the material, StreetBond® DuraShield Pavement Coating, and Asphalt Impressions, Inc., a Sacramento-area contractor, has agreed to donate their labor to apply the cool pavement coating material.

StreetBond® DuraShield Pavement Coating is a cool pavement coating that reflects a higher portion of the sunlight that hits it, hence absorbing less heat. Because of this higher reflection, the coating has the potential to offset rising temperatures in the region.

As part of the Climate Action and Adaptation Plan (CAAP), the City of Davis is taking actions to assess greenhouse gas (GHG) reduction progress made since the 2010 CAAP adoption, identify physical and social vulnerabilities, establish and prioritize climate action and carbon reduction policies toward carbon neutrality, and bring the City into compliance with current state legislation. One of the City’s goals is to develop an ordinance to require the use of cool surfaces, reflective materials, and coatings to reduce the heat island effect. Heat islands are urbanized areas that experience higher temperatures than outlying areas. Structures, such as buildings, roads, and other infrastructure absorb and re-emit the sun’s heat more than natural landscapes, such as forests and water bodies. The cool pavement demonstration project is the first step in moving toward a larger pilot project and finally meeting the goal of requiring the use of cool and reflective materials to reduce the heat island effect.

Phoenix, Arizona is one of several cities that have implemented a cool pavement pilot project, and provided findings from year one of their cool study, which include:

• Cool pavement revealed lower surface temperatures at all times of the day versus traditional asphalt.
• Cool pavement had an average surface temperature 10.5 to 12 degrees Fahrenheit lower than traditional asphalt at noon and during the afternoon hours. Surface temperatures at sunrise averaged 2.4 degrees Fahrenheit lower.
• Sub-surface temperatures averaged 4.8 degrees Fahrenheit lower in areas treated with cool pavement.
• Nighttime air temperature at six feet of height was on average 0.5 degrees Fahrenheit lower over cool pavement than on the non-treated surfaces.
• The human experience of heat exposure at noon and the afternoon hours was 5.5 degrees Fahrenheit higher due to surface reflectivity, but similar to walking on a typical concrete sidewalk.
• Surface solar reflectivity declined over 10 months from a range of 33 to 38 percent to a range of 19 to 30 percent across all eight neighborhoods within the pilot program. Untreated asphalt has a reflectivity of only 12 percent.

The City of Davis is excited to implement its first cool pavement project and making progress toward implementing a climate action plan goal that will help the City >prepare for the impacts of climate change in our community.

What is cool pavement?

It is a water-borne acrylic-based coating that is applied on top of the existing asphalt pavement. It contains no harmful chemicals and is compatible with traditional asphalt.

Why would Davis apply cool pavement?

• Asphalt collects and retains heat during the day and releases it at night. Many cities experience the urban heat island effect due to the retention of heat within the built environment. The U.S. Environmental Protection Agency data shows the difference in nighttime temperatures in heat island areas can be as much as 22 degrees warmer than temperatures measured outside the heat island. Higher nighttime temperatures lead to more energy consumption, more greenhouse gas emissions, air pollution and other harmful effects.
• Cool pavement reflects back the sunlight that hits it. Because the surface reflects rather than retains heat, cool pavement has the potential to offset rising nighttime temperatures in Davis. The use of cool pavement technology may help reduce the heat island effect and reduce temperatures in the city. It is also useful to cool neighborhood areas that don’t have much shade from the sun.
• Cities such as Phoenix and Los Angeles have been using cool pavement on neighborhood streets and have reported positive results in reducing roadway surface temperatures.

Why is this a demonstration project?

The City of Davis wants to test the cool pavement technology and material to see whether it is effective at reducing temperatures in Davis. City staff plan to take measurements and collect data over the next year to determine the effect on asphalt temperature. The City also hopes to implement a larger pilot study which will allow for continued study to determine if the cool pavement product mitigates the heat island effect and if those effects are sustainable over time. 

Where are you testing cool pavement?

• Thermal imaging collected from the summers of 2019 and 2020 are available on ArcGIS, a web-based mapping software. Using this data along with the City of Davis Public Works Engineering & Transportation Department’s prioritization for maintenance and rehabilitation projects, the Olive Drive Parking Lot was selected as a candidate for the demonstration project. As part of a pilot study in the future, the City hopes to identify additional local streets in various neighborhoods around Davis using similar methods to how well it is working and how durable it is.
• Ideally the streets selected for the pilot project should have asphalt that is in good condition, but where a preservative surface treatment is warranted. Preservative treatments extend the life of the road by sealing any surface cracks to prevent moisture intrusion and improve the overall road condition and appearance.

How can my street or neighborhood be selected for future cool pavement applications?

• Pavement condition is one of the key criteria for future installations. We will also try to solve community challenges, such as providing heat relief to areas with very little shade. Future installations will be studied to ensure the cool pavement is placed equitably and in areas where the immediate benefit is most needed, such as areas with little or no shade or areas where people move on foot or bicycle out of necessity. Cost will also be a consideration as the City works to use taxpayer funds wisely.
• While the cool pavement material is more expensive than some other seal coating materials, results from other cities suggest the material is more effective and longer lasting than traditional asphalt seal coats. If the material provides the environmental benefits we believe it will, the City hopes to see wider use of cool pavement when neighborhood streets are due for pavement maintenance. 

Can I buy the cool pavement material and treat my driveway with it?

• StreetBond Durashield by GAF can be used directly on asphalt driveways and on concrete with a primer. The temperature reduction is most effective over black asphalt driveways. Although it is sometimes used on concrete, the cooling benefit is minimal since concrete is lighter in color than asphalt and already somewhat cooler.

Does cool pavement look different than traditional asphalt?

• StreetBond Durashield by GAF is designed to resemble aged asphalt and is medium gray in color.

Is cool pavement safe to use?

• It is safe for all types of vehicles, pets, people and all the typical activities that would take place on a road. Despite being lighter in color, cool pavement does not result in glare. It also meets or exceeds skid safety requirements.

Is this a new product?

• GAF StreetBond has been used since the mid-1990s, mostly on decorative applications like crosswalks, bike lanes, and bus lanes. The technology has been specifically designed and colored for neighborhood streets.

How is cool pavement applied?

• It is spray applied with special equipment to prevent overspray.

Who are the partners in this project?

• The City of Davis Public Works Engineering & Transportation Department are partnering with GAF, is the vendor donating the StreetBond® DuraShield Pavement Coating, and Asphalt Impressions Inc., that is donating labor to apply the pavement coating, to learn if this project can help with the City’s continuing efforts to be environmentally sustainable while improving the quality of life for all who live in the region.