Civil Engineering Reference
In-Depth Information
outdoor air, although this appears to be a secondary cause of the UHI effect) and
influence on the health and welfare of residents (Urban Heat Island 2009).
As Smart-ECO strategies suggest the importance of compact cities, it is impor-
tant to approach the question holistically and avoid potential negative effects
deriving from the densification of urban areas. There are two main strategies that
may help reduce UHI effects: (1) cool roofs and paving materials; (2) green roofs
(Berndtsson
2010
).
Both strategies are relatively common and well experimented, but it is their
large-scale application that can make a difference at the urban scale.
The use of light-coloured or cool roofs leads to measured energy savings (cool-
ing) of 10-40 % in buildings with significantly large roofs. For example, the
extension of roofs with high reflectivity to all of the US would lead to overall sav-
ings of US$750 m with related lower carbon emissions.
Green roofs have several positive effects in the urban setting in addition to
reduce urban heat islands (Carter and Keeler
2008
): to improve stormwater man-
agement by reducing surface runoff and improving water quality, (Mentens
2006
),
to reduce building energy consumption by cooling roofs during summer months
(Palomo del Barrio
1998
), to reduce noise and air pollution (Bradley Rowe
2011
)
and create habitats for certain plants and animals and thereby improve urban bio-
diversity. Moreover, analysing energy saving, construction, replacement phase and
surface albedo, both white and green roof result in less impact than the black roof
(Kosareo and Ries
2007
; Susca
2009
; Susca et al.
2011
).
Studies on the UHI in the city of Milan showed that, during the last century,
winter temperatures increased by 2 °C, and in summer the difference between diur-
nal and nocturnal temperatures decreased. Substituting existing roofs with green
roofs in the industrial areas, a potential decrease of air temperatures of 2 °C was
estimated (Poli et al.
2007
). Smart-ECO innovations should be directed towards the
implementation and diffusion of such systems at a large scale in urban areas.
Example: The R.I.E. Index
The City of Bolzano in northern Italy introduced the
R.I.E. (Riduzione dell'Impatto Edilizio—Reduction of Building Impact) Index
that is intended to be a numerical index of the environmental quality. It is applied
to a building lot to assess its environmental quality considering soil permeability
and green extent.
I
=
1
SV
I
1
+
(
SE
)
RIE
=
I
=
1
SV
I
+
J
=
1
S
IJ
where:
Sv
i
green
permeable, impermeable or sealed;
Si
j
not green
permeable, impermeable or sealed;
Ø
coefficient of flow;
Se
equivalent surface of trees.
It expresses the ratio between the elements modifying the land use and the manage-
