Volume 92, October 2015, Pages 305–316
Plant cover and floristic composition effect on thermal behaviour of extensive green roofs
Highlights
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- Thermal performance of extensive green roofs was investigated.
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- Plant cover and floristic composition analysis were carried out.
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- Results show temporal and spatial changes in plan cover and floristic composition.
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- The importance of the spatial effect in extensive green roofs was highlighted.
Abstract
In
the last few years an increasing attention has been paid to efficient
energy construction systems in the building sector. Although in this
contest extensive green roofs are reported to be very effective and
sustainable systems, the fact that the main agents of this systems are
living organisms have generated doubts, especially in locations where
the development of plants and vegetation can be greatly affected by
climate. This study aims to investigate the thermal performances of a
2000 m2 particular proprietary extensive green roof system,
located on the city of Lleida (Spain), classified as Dry Mediterranean
Continental climate. First, plant cover and floristic composition
analysis were carried out to evaluate the dynamic of the plant layer
over the surface. Then, according to the result of the botanic analysis,
summer and winter study in terms of spatial and temporal factors were
conducted focussing on the substrate layer, evapotranspiration effect
and comparing the different behaviour of the system in low (10%) and
high (80%) plant cover conditions. In this extensive green roof, the
results showed temporal and spatial changes in floristic composition,
with a stable cover of Sedum sp between 20 and 40 %, and a peak of
colonizing species in spring and early summer. The increase in
vegetation cover appears to have few effects on the above nearby roof
environment because of the low moisture level in the substrate layer so
that the cooling effect provided by the evapotranspiration does not take
place. In addition, the increased presence of vegetation canopy may
induce a limitation in substrate night cooling whereas serves as good
shield for solar radiation during the day. Finally, the study also
reveals the importance of the spatial factor in extensive green roofs,
which can lead to not negligible variations on the thermal performance,
as well as the floristic composition.
Keywords
- Plant cover;
- Floristic composition;
- Thermal behaviour;
- Extensive green roofs
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