The Urban Heat Island Effect and How Green Rooftops Can Help

It's awfully hot in the summer, and the last few years have seen a rise in a number of adverse side effects to the heat: soaring utility bills, and the increased risk of heatstroke among small children and the elderly.

Many American cities are feeling the effects of what the Environmental Protection Agency describes as the "urban heat island" effect.  In developing cities, lands are cleared to make way for progress in cityscapes, and often the environment suffers in the concrete jungle.  When vegetation is wiped out, the buildings and streets and sidewalks that take their place have no way to regulate their temperature.  On hot days the temperature of roofs and sidewalks can reach dangerous temperatures ranging 50-90 degrees warmer than the air outside according to the EPA.

This is the kind of weather you hear people say is "warm enough to fry an egg on the sidewalk" and it's becoming more the norm than the exception.  The National Resources Defense Council (NRDC) projects that we will be looking to average summer temperatures anywhere from 4-11 degrees warmer in the United States by the end of the century in their report "Killer Summer Heat."  The study documents research of excessive heat event days in 40 of the largest US cities and divides the results into two separate projects.  In project one with a timetable of 1975 and 1995, there was an average of 233 excessive heat event (EHE) days in the historical records of the studied cities.  EHE days are classified by the combination of temperature and other weather phenomena that leads to heat-related deaths.  By 2099 it is conservatively estimated that those cities will experience the combined total of 1,918 EHE days, an eightfold increase.
then projects the increase of excessive heat event days for future decades.

The second part of the project estimates how many more deaths will occur on EHE days, and the numbers are not pretty.  Between 1975 and 2004, 1,332 deaths were linked to EHE days.  By 2099, the number will raise to just over 150,000 yearly deaths from heat in the United States.

These are staggering numbers, and we have to look at our socio-economic structure to really understand why these numbers are often left out from the nightly news.

If you can't afford to pay for the rising costs of cooling your home in extreme heat, you might be faced with loss of electricity.  The CDC offers the following (paltry) tips for dealing with high temperatures if you are in a low income bracket:

• If you have air conditioning, use it to keep your home cool (Really?)
• If you can't afford to use your air conditioning:
  Contact your local health department or locate an air-conditioned shelter in your area.
  You can also contact LIHEAP for help
• Drink more water than usual and don't wait until you're thirsty to drink.
• Check on a friend or neighbor, and have someone do the same for you.
• Seek medical care immediately if you or someone you know have heat-related illness symptoms. 

Now, all of that seems pretty common-sense, but it really sounds like they're saying if you can't afford to keep cool, hope more water helps, and get a buddy system in case one of you dies from the heat, you'll at least be found quickly.

Last summer, the air conditioning went out in the house I was renting.  Temperatures soared and I received a $300 electric bill for a single month's energy consumption when the outside cooling unit needed to be replaced.  Fast forward almost a year later and I'm still paying that bill off over a payment plan.  I'm one of the lucky ones; I could afford to negotiate the bill.  There are thousands who are not as fortunate, and they need a lifeline.  Death shouldn't be the only option when it gets hot outside, but as reported in Scientific American, if you're poor, good luck.  

According to the U.S. Green Building Council, low-income households spend almost 20% of their income on utility bills in average conditions, compared to 4.5% middle-class households typically spend under the same conditions.  

As urban sprawl and the heat effect become more problematic, solutions are emerging in greenroof technology.  

The above picture is of Chicago's City Hall and the green roof technology.  Construction started in 2000 and was completed in 2001.  The initial expense of the garden was $2.5 million dollars.  The building now saves over $5,000 a year in energy costs.  

Startup expenses can be staggering to some, but the CDC cites a study from the University of Michigan comparing conventional roofs to green roofs, and what they have found is green roofs initially cost more, but will almost earn back their original costs in energy savings over their expected life.  A conventional roof offers shelter from the elements, but still requires insulation and other installation commodities that offer no incentives for utility bills or environmental benefits.  Cities that utilizing green roofing in their architectural design for low-income housing also experience the benefits of green roof tax incentives that help recoup a great portion of the initial cost while still providing affordable housing (and reduced utility bills) to clients.