Rethinking Infrastructure Design - Rethinking Infrastructure Design for Multi-Use Water Services - page 16

Fig. 17 Combined measures for energy efficiency and UHI mitigation

Results are promising from a pilot project in three US cities (Chicago, Portland and
Philadelphia). According to US-EPA ( 2012 ), by implementing a green roof at City
Hall in Chicago, they have gained positive improvements in: (a) energy saving (in
electricity 9,271 and 7,372 KWh/year in terms of heating); (b) improvement in air
quality; (c) up to 70 % reduction in storm water load; (d) increase in biodiversity, etc.
The raised temperature in urban areas directly increases energy required for air
conditioning and refrigeration in summer. This problem can be mitigated (Fig. 17 )
by combination of active and passive measures. These may include storing surplus
thermal energy in summer (to be recovered in winter together with heat from
wastewater) and using the shade and evaporative cooling of (blue) green roofs and
walls and tree lines planted in an optimised fashion. Some of these effects can be
illustrated by the results of monitoring in Florida to measure the energy saving from
urban tree planting. It was found that up to 50 % of cooling-electricity is saved for a
building after the addition of trees and shrubs (Meerow and Black 2005 ). By
reducing the need for air conditioning, anthropogenic (manmade) heat is also
reduced. That means that, as a feedback, less heat is pumped back into the urban
environment.
By combining MUS solutions in the streets and on buildings the properties of
urban materials such as albedo, thermal regime, emissivity and speci c heat

capacity can be drastically improved. The ones that in uence solar radiation;

emissivity and absorption, thus reduce the UHI effect.