DEEGAN ON LA-Have you ever heard of an “urban heat island?” Do you know how it affects our environment? Do you know how developers can use carbon management techniques to help offset the effects of the heat and carbon impacts generated by the tall vertical masses they want to build?
This term is part of a new vocabulary of climate consciousness. Heat generated by buildings is becoming a pressing environmental issue – and it’s beginning to smother and suffocate us the way urban smog once did in the Los Angeles basin and the Valley a generation ago. Back then we could see the smog; now, we can feel the heat.
The environmental impact of urban heat islands needs to be recognized, and their effects controlled, especially as our city becomes denser and more tall buildings are creating these urban heat islands.
So exactly what is an urban heat island? Atmospheric experts, such as UCAR (The University Corporation for Atmospheric Research), a consortium of universities and colleges offering degrees in the atmospheric sciences, provide some clear language as to what constitutes an “urban heat island”: “An urban heat island (UHI) is a metropolitan area which is significantly warmer than its surroundings.” They note that EPA (Environmental Protection Agency) stats show that cities generally have air temps 10 degrees warmer that the surrounding land cover.
As the development debate expands, we’ll be looking at how land is used and how zoning is enforced (or short-shrifted,) and whether our building programs trend vertically or maintain the horizontal low slung profile that has characterized much of LA over the years. As we consider the nature of our future cityscape, we’ll need to decide how to adapt to changing climate needs…especially if we build more vertical structures. The control of heat and the gas emissions that emanate from regulating it must be considered and mitigated.
This is an issue that rarely gets much public attention in Environmental Impact Reports, but as we witness more crazy weather patterns and experience a global shift in the health of our environment, it may boil down to one major activator: heat.
The cycle is simple: the sun shines, our buildings either absorb or reflect its heat depending on the sheathing of the building; the air-conditioning of the building cools the insides by extracting heat and this is sent back into the atmosphere in the form of a gas, adding to the city’s carbon impact.
Air conditioning and refrigeration principles are basic: heat is extracted from the space being cooled. Excess heat is sent into the atmosphere in gaseous form. The White Roof Project reports that “one-sixth of all electricity generated in this country” is to power air conditioning. That process does remove heat but it also sends the refuse into our atmosphere. That ratio may be larger for us here in Southern California where the sun shines almost every day of the year; and with our extra-long, intense summer heat, we have air conditioners running 24/7.
We need to localize this phenomena to our city and make sure “development dreams” include looking at the “heat islands” we create. How does this degrade our environment – even setting aside other known concepts such as the hole in the ozone layer, the threats of flooding from El Nino, or the melting polar icecaps that could cause the sea level to rise, turning beachfront communities like Malibu and Venice into swamps?
Picture our hillside urban centers surrounding the Santa Monica Mountains and you get a sense of where our current heat islands are. As the city densifies we will see new heat islands created on both sides of the hills.
But heat islands can be controlled depending on how we develop land surface and how we manage the off-throw of heat not used for energy. Unimproved land -- and there are huge stretches of it in both the Valley and the basin sides of the Santa Monica Mountains, as well in the mountain range itself -- consists mainly of vegetation that reflects heat and helps to slightly lower temperatures. Conversely, developed areas absorb the sun's heat, causing surface temperatures and overall ambient temperatures to rise. Less trees and more tall buildings create change in temperature for an entire community.
Do “White Roofs” help? There may be divided opinion about the effect of painting roofs white to reflect heat away from the building. Anyone who wears black, a very popular wardrobe choice in super-sunny Southern California, knows how that dark colors absorb the heat, while white reflects the sun; light colors have traditionally been a summer clothing choice for that reason.
The White Roof Project, is an experimental volunteer project that was founded several years ago in New York City where “heat canyons” abound. They say that “a white roof painted with solar reflective white coating reflects up to 90% of sunlight (as opposed to traditional black roofs which reflect only 20%.)” It’s a good argument for one method that may help tamp down the temperature of heat islands.
Another “solar control” being used in tall buildings is reflective glass. It helps to reduce solar heat gain and manage solar heat radiation, while contributing to the aesthetics of the building. On tall buildings, the type that are dreamed of for our city, heat-sensitive glass facades can really help; this may be one of the best solutions for controlling heat islands.
When it comes to considering the effects of heat islands created by building new tall structures, perhaps a hybrid building plan will help developers and activists reach a compromise. Implementing solar controls as we build taller buildings may require new designs for building facades, using much more reflective glass to minimize carbon impact.
World-famous Southern California sunsets – increasingly reflected against canyons of glass -- just may become a new iconic image for Los Angeles.
(Tim Deegan is a long-time resident and community leader in the Miracle Mile, who has served as board chair at the Mid City West Community Council and on the board of the Miracle Mile Civic Coalition. Tim can be reached at email@example.com.) Edited for CityWatch by Linda Abrams.