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08 - Green roofs on public buildings in the Netherlands |
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Project name
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Green roofs
in The Netherlands
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Fig. 1: Library of the University of
Technology Delft (TUD). A green
roof in the form of a lawn as a recreational area |
Keywords
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Roofs
covered with vegetation or the creation of green space on top of a human-made structure.
There are two basic types of green roof systems: extensive and intensive.
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Start of the project
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TUD: 1997
PWN: 1999
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End of the project
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Still existing
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Contact person
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TUD: www.library.tudelft.nl (Prometheusplein 1, Delft)
PWN: www.pwn.nl (Johannisweg 2, Castricum)
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Short project description/ project function
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Roofs can
be covered with different type of vegetation.
Extensive
'green' roofs with moss-, Sedum- and herb vegetation, which can survive long
periods of drought, has a thin layer of soil.
Intensive
'green' roofs consists of a thicker layer of soil with more favourable conditions for
plants.
The
thickness of the soil and the intensity of human use determines the weight.
The greater the weight the higher the costs.
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Fig. 2: Visitor Centre of the
Provincial Dunes of North Holland (PWN).
A green
roof fully integrated into the surrounding dune landscape. |
Summary of experiences
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The
'green' roof of the TUD-library is of a lawn type. In this case the architect
did not like
flowering plants on the roof. Although this approach is a step forward of
greening the city,
the ecological value is minimal. The
'green' roof of the PWN-Visitor Centre is fully integrated in the surrounding vegetation
and has a high ecological value. The original Sedum dominated vegetation has
gradually been changed in a more complex dry dune vegetation of the
surroundings.
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Project
benefits
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Positive
effects of vegetated roofs:
- Improvement of air quality
(Collect air pollution -dust, smog, NOx -)
- Reduction of water discharge
due to water taken up by plants partly for assimilation and partly for evaporation
- Reduction of peak loads of
heavy rain
- Conservation of habitat and
biodiversity
- CO2 uptake and O2 production
- Noise reduction
- Temperature regulation;
moderation of the urban heat island effect
- Creating microclimates and
microhabitats
- Aesthetic improvements
- Recreation space
- Better living conditions
inside the building (insulation, reduction of noise).
The
'green' roofs need regular (mostly low labour intensive) maintenance.
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Project
level
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Mature
technology
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Financial
scale
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Cost of construction
and maintenance for the TUD 'green roof' and the PWN
'green' roof : unknown
Costs in
general for 1000 m2 with a soil layer of 12 cm (Sedum, grasses- vegetation
mats) the construction costs are ca. 60
Euro/m2 and for a 'normal' gravel roof ca. 50 Euro/m2. A more intensive green
roof costs ca. 100 – 150 Euro.
More
details can be found on the available green roofs or rooftop websites. A
general introduction can be downloaded from www.lwg.bayern.de (in German).
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Environmental conditions
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Both
buildings with 'green' roofs are situated in the western part of the
Netherlands, influenced by a maritime climate
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Altitude
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Sea-level
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Description of special local conditions
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The TUD
green roof is situated in an urban area, the PWN green roof in a more natural
landscape.
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Why this is ecological engineering
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Plants
and animals on 'green' roofs can make an important contribution to the improvement
of ecological values and water-management in rural as well as in urban areas. It
is also beneficial for the
climate regulation within the top floor of the building. It is an integrated approach where
different services of nature are combined which are
useful for humans and nature as well.
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Last Updated ( Tuesday, 18 December 2007 )
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