On June 6, 2001, the Chicago City Council approved an ordinance
that substantially revised the Municipal Code of Chicago. Included
in the ordinance was an upgrade of the code's existing insulation
requirements to require compliance with ASHRAE Standard 90.1-99,
"Energy standard for buildings except low-rise residential
buildings," and add prescriptive provisions that required low-slope
roof systems to have an initial solar reflectance of 0.65 and
maintain a solar reflectance equal to or greater than 0.50 for
three years after installation.
Given that Chicago historically has been a bitumen-based roofing
market, with built-up and polymer-modified bitumen membrane roof
systems making up a majority of the low-slope roofing inventory,
this ordinance's minimum solar reflectance requirement, in effect,
mandated a major change in roofing material and product usage in
The ordinance initially was passed by the Chicago City Council
with virtually no notice to or input from the roofing industry.
Also, the city initially indicated the ordinance was intended to
modernize the city's energy code with a focus on improving energy
efficiency while providing for flexibility in building design.
Subsequently, city officials also acknowledged a large motivation
behind the ordinance was an attempt to reduce the urban heat island
phenomenon in downtown Chicago.
What follows is an account of our participation in helping
revise the city's energy code. We have adapted our research paper,
"Study of roof system reflectivity and near-surface air
temperatures in Chicago, Illinois," that we presented at the Cool
Roofs Symposium in May in...
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