New technology, CoolSeal resurfacing designed to make parking lot temperatures cooler, is being tested in the De Anza north east parking lot.

CoolSeal has been applied to counteract the urban heat island effect, which is a phenomenon where urban areas experience significantly warmer temperatures than surrounding rural areas. This is primarily due to the dense concentration of buildings, roads, and other heat-absorbing surfaces that retain heat, along with the heat generated by human activities like cars and air conditioning.

Minimizing urban heat in cities is crucial because it reduces increased energy costs, air pollution, and heat-related illnesses, while also improving overall comfort and resilience to climate change.

CoolSeal is a high-performance, water-based, asphalt-emulsion designed to achieve lower surface temperatures through its lighter color and reflectivity. CoolSeal meets Environmental Protection Agency and LEED requirements, a globally recognized green building certification system, of 33% reflectivity. It can also last longer than conventional seal coats.

Of CoolSeal and its impact, City senior spokesperson Tyler Becker noted: “The lighter the color, the more reflective the surface, and in turn, the greater reduction in the heat island effect. Light gray allows for a large amount of heat reflection and does not produce as much glare as white surfaces.

“The difference in open areas, like the De Anza parking lot, is that they have a greater heat island effect since they receive more direct sunlight,” Becker said. “Other potential sustainability advantages of using the coating in an open parking lot include an increased longevity of the pavement, as it reduces heat extremes and the maintenance cost of pavements.”

Regarding CoolSeal, Becker noted: “The product is a reflective coating designed to help reduce the heat impact of a given surface. While the CoolSeal application is an element of the De Anza north east parking lot project, the main benefits that residents and visitors will be able to utilize for years to come are the repaved parking lot and accessibility upgrades. These improvements were crucial to best serve the community, especially in such a popular coastal location.”

The new CoolSeal technology supplements other efforts to lower the urban heat island effect. Other cities, like Los Angeles, Phoenix and Dallas, have spent millions on similar cool pavement technologies. San Diego is just beginning to try it out. The De Anza Cove work is part of a pilot program to add reflective surfacing to two parking lots. The second lot is also along Mission Bay at Sunset Point Park.

Becker pointed out the full resurfacing project at the De Anza north east parking lot cost $3,024,577, and, of that total project cost, the CoolSeal product and application cost $144,000.

“These funds came from the Mission Bay Park Improvements Fund,” Becker said adding, “The De Anza north east parking lot project is the first and only City project so far to have the CoolSeal product applied. The pilot program is to test the viability of using the reflective coating and study the application process, constructability, maintenance issues, impacts on asphalt paving, cost and potential sustainability advantages. Other potential sites for use of CoolSeal are on hold until more data is gathered from the De Anza site.”

The urban heat island effect: Refers to urban areas experiencing significantly warmer temperatures than surrounding rural areas. The difference is 1-7°F warmer during the day and 2-5°F warmer at night.

Causes: Urban surfaces like asphalt, concrete, and buildings absorb and retain heat from the sun during the day, then radiate that heat back into the air, especially at night. Cities generally have less vegetation compared to rural areas, reducing shade and the natural cooling effect of water evaporating from plants. Activities like traffic, air conditioning, and industrial processes contribute to the heat island effect by releasing waste heat into the environment. The dense, compact layout of buildings can also trap heat, creating “urban canyons” that limit air flow and further contribute to the temperature increase.

Consequences: Higher City daytime and nighttime temperatures compared to rural areas lead to increased thermal stress on residents. Higher temperatures necessitate more energy for cooling (air conditioning), increasing electricity demand and related costs. Higher temperatures can exacerbate air pollution by increasing the formation of smog, which can trigger respiratory issues. Heat-related illnesses like heat stroke and heat exhaustion become more prevalent, particularly among vulnerable populations. Urban heat islands can affect urban ecosystems reducing the quality of life.