Urban Heat... as pollution?

Interestingly enough, most of my classes this week seem to centralize around the theme of atmospheric change.  Something that relates really well to atmospheric change and has piqued my interest recently is the urban heat island effect.

Here's a fun little graphic to demonstrate my point.

The urban heat island effect (UHI) is essentially when the center of an urban area is significantly warmer than the adjacent rural areas.  As you can probably imagine, there are a myriad of sustainability issues that are impacted by UHI, including water and electrical use.  For example, an article I read for another class (the abstract is here) looks at the impact of the UHI effect on residential water use in Phoenix, Az.  They compile data into two log-linear models and find that variables like mean lot size, household income, mean age of housing, percentage of units with an evaporative cooler (an alternative to traditional air conditioning), and mean pool surface area.  The article points out that UHI has both indirect effects, due to the increased amount of energy being used, as well as direct effects, which include higher outdoor demand for water use (to fill those wonderful pools).  To put this into perspective, researchers found that for each 1,000 square foot increase in size of lot, the average water use increases by roughly 1.8 percent and a 1 degree Fahrenheit increase in temperature results in a roughly 290-gallon increase in water usage per single-family residence, which obviously has incredibly large impacts on the environment and sustainability that need to be addressed.  That's huge. 

Huge pool = higher water use.

So, how do we mitigate this effect?  Well, the authors provide a few suggestions, like heavier zoning regulations that specify lot size, or regulations on the size of outdoor swimming pools allowed.  They also include four suggestions that are specific to an urban planner:
1) Looking at a city's form and structure, ie. the alignment and planning of roads or the amount of space between buildings;
2) Use of materials used in building, especially taking into consideration thermal efficiency and reflective vs. absorptive surfaces;
3) Land cover, including the amount of natural land cover being affected by the building; and
4) The geographic and cultural context of the area in question, i.e. what natural resources are already present.

Phoenix, Az.  Really pretty, and really hot.

Something that they don't cover in this article very well is what to do to mitigate the problem in existing places.  I would have liked to learn about mitigation strategies being used on existing structures in order to downplay the negative effects of the UHI.      


Finally, one thing that really caught my eye at the end of the article is the fact that the authors point out that if heat were to be considered a pollution, it could be properly regulated.  I had never thought of heat being a type of pollution, so this struck me as odd.  I couldn't find anything about heat being a pollutant on the EPA website, but Wikipedia does have some more information.  Do you guys think that heat (human-made) should be considered a pollutant?


If you are more interested in the UHI effect (I'll be honest, I totally geeked out a little when I started learning about it), the EPA has some information on the subject.