Curbing California's Urban Heat Islands

[courtesy of California Progress Report]

The Temp’s Rising -
Do you live in an Urban Heat Island?
How to turn your ‘urban heat island’ into a ‘cool city’

By Loni Hancock
Chair
California State Assembly Natural Resources Committee

Every summer, sweltering heat is accompanies by elevated levels of smog and increased health risks. Inner core cities will be up to 10° hotter due to what scientists at Lawrence Berkeley National Laboratory (Berkeley Lab) have labeled the ‘urban heat island effect.’ Urban heat islands are significantly warmer than their surrounding undeveloped areas as a result of vegetation being replaced by buildings with dark colored roofs and asphalt roads that absorb heat.

Although the causes of urban heat islands are distinct from global climate change, the two phenomena are related. Urban heat islands intensify the effects of global warming in urban areas. Higher temperatures lead to increased air conditioning. Air conditioners are a significant and growing contributor to greenhouse emissions that promote global warming.

Fortunately, there are several easy and inexpensive actions that we all can take to cool cities and suburbs, such as installing cool roofs, selecting cool paints, using cool pavements and planting more trees. For these reasons I have introduced Assembly Bill 785, legislation that will result in reduced temperatures and energy use, creating a healthier and cooler atmosphere for California urban areas. Assembly Bill 785 requires contractors to comply with existing energy efficiency standards on remodeling projects and adds penalties to those who ignore energy efficiency building regulations.

The first step we can take is to install ‘cool roofs.’ Buildings with cool roofs reduce the urban heat island effect. Cool roofing material contains a highly reflective substance that reflects solar energy back out into the atmosphere and discharges stored heat rapidly. Compared to traditional roof surfaces, which can get as hot as 190° on hot summer days, cool roofs stay up to 70° cooler and discharges stored intense attic heat. The benefits of cool roofs are numerous, keeping inside temperatures – and cooling costs – down.

A second promising approach we can take is to purchase vehicles with highly reflective exterior paint colors. ‘Cool colors’ such as white, metallic silver and metallic gold reflect sunlight back into the atmosphere resulting in a cooler vehicle cabin and reduction in air conditioning, fuel and vehicle emissions – providing cleaner healthier air. Berkeley Lab, the State Air Resources Board and the State Energy Resources Conservation and Development Commission are developing highly reflective exterior paints, in colors other than white, metallic gold or metallic silver. Their continued work will offer plenty of alternatives to consumers in the near future.