What Are the Main Options for Applying the Multiple-Use Water Services Paradigm? - Rethinking Infrastructure Design for Multi-Use Water Services - page 35

5.6 Why Green Roof and Green Wall Systems?

Mitigation of Urban Heat Island Effect — Reduced air temperature through shading,

evaporation and light absorption provided by plants.
Enhanced air quality by capturing airborne pollution, harmful gases and volatile
organic compounds and providing thermal insulation inside buildings resulting in
reduced energy demand for heating and thus less CO 2 released into the air.
Increased biodiversity in an urban environment — Green roofs and walls can
sustain a range of vegetation and serve as habitat and nesting place for different bird
species.
Local job creation in the fields of design, manufacturing, installation and

maintenance.
Enhanced aesthetics, amenities and recreational green spaces (e.g. community
gardens, playgrounds in green roofs) and increased property values of buildings.
Storm water retention and water filtration through green roofs —

Green roofs
can return 50 % of annual precipitation back to the atmosphere through retention
and evapotranspiration (Berghage et al. 2009 ). In addition to reducing the volume
of storm water run-off, a green roof can successfully delay the time to peak, leading
to less stress on sewer systems at peak

flow periods.
Thermal insulation and energy savings — In summer, an extensive green roof can

reduce daily energy demand for air conditioning during summer by 75 % (Liu and
Baskaran 2003 ).
Noise reduction —

Vegetated vertical and horizontal surfaces can block high-fre-
quency sounds and when combined with a substrate or growing medium can block
low-frequency sounds. Extensive and intensive green roofs can reduce sounds from
outside the building by 40 and by 46 - 50 decibels, respectively (Peck et al. 1999 ).

Fire Retardation — Green roofs are found to have better fire resistance values

ö

compared to conventional roofs (K hler 2004 ).

c design green roofs and walls are suitable for
growing fruits, vegetables and herbs.
Extended roof life —

Urban agriculture — With speci

ng mem-
branes from the effects of UV light, mechanical damage, high thermal temperature

Green roof systems provide protection to roof

fluctuations therefore leading to a longer lifespan.
Reduction of electromagnetic radiation — Green roofs can reduce electromag-

netic radiation penetration by 99.4 % (Herman 2003 ).

6 Urban Agriculture

Urban agriculture is generally the practice of cultivating crops for food in cities.
Growing fruits, vegetables and herbs in cities can be combined with other green
infrastructure (green roofs and walls) and decentralised water management tech-
niques (RWH) (Fig. 6 ).