Review and Critical Analysis of International UHI Studies

controls of the active cooling/heating systems and building insulation appeared to be neglected in
the literature reviewed to date.
4.5.2.4 Status of Cool Pavement Policy Review
The status of cool roofs policies is far more advanced than cool pavements. Currently few policies
exist in this area with the exception of the LEED Green Building Rating System which provides
credits for buildings using cool pavements through its Sustainable Sites Credit. A scheme in
Chicago called the Green Alley Initiative uses porous paving materials whenever an alley needs
to be repaved, this was borne from a demonstration of the benefits by the City of Chicago [076].
On a residential level the Earth Craft Homes program, developed by the Greater Atlanta Home
Builders Association and Southface Energy Institute, awards points for homes that use permeable
pavements [076]. A reason for this could be that not enough research and modeling has been
undertaken, both technical and economic, and a lack of support from the government and
institutions for this technology with most of the focus being on cool roofs.
4.5.2.5 Critique of Cool Pavement Literature and Emerging Issues
The cool pavement research predominantly has a US focus with a small emphasis in limited parts
of Europe, with a majority of the research originating from the Lawrence Berkley National
Laboratory UHI Group. This has therefore resulted in a concentrated field of research centered on
North America. Thus any field experiments, modeling and simulations of the range of cool
paving materials were predominantly evaluated in a limited range of climate types found in
North America.
A majority of the studies used the case study approach and concentrated on evaluating the
collective benefit of increased albedo for roofs, pavements and often shade trees and vegetation ‐
it was therefore difficult to isolate the indirect savings (energy, peak power and CO2) that could
be attributed to cool pavements. Such aggregations of mitigation measures added to the problem
complexity. The studies indicated that the challenges faced in measuring cool pavements as
opposed to cool roofs are significant simply due to the complexity of measuring the pavement’s
influence upon building energy demand ‐ this implies that there still remain significant
challenges to be overcome in establishing such estimates. Only one study tried to isolate and
quantitatively assess the effects of paved surfaces on the near surface atmospheric model – this
remains critical to understanding how pavements affect the atmospheric temperature [127]. The
modeling of radiative and thermal characteristics is highly complex but essential for accurate
estimates, it is critical that the influencing factors are understood, quantified and field data is
collected – these steps are essential in helping engineers, designers and planners make the
appropriate designs and selections in cool paving technology and implementation.
In the LBNL study, the estimates seek to present the effect of increasing world‐wide albdeos of
urban roofs and paved surfaces during the summertime by inducing a negative radiative forcing
on the earth in terms of CO2 emissions offsets. They estimate that by increasing the net albedo by
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