Observations on the roof indicated than that of the sedum-dominated The research from Project SmartRoof
that the Sedum vegetation on the vegetation. 2.0 demonstrates that in order to
conventional green roof ran out
of water after 6-7 days of no rain,
where the Blue-Green systems with
grasses and herbs ran out of water
after a dry spell of 15 days.
To achieve maximum evaporation
to maintain the growth of roof
vegetation and to generate the
urban cooling effect, based on 80mm
of water storage, 70mm of extra
have the urban environment benefit
of green roofs, we have to add water
to these systems so plants can
flourish. A Blue-Green roof system
also enhances how urban space can be
better used in a multifunctional way.
The results found that a conventional irrigation water would be needed for a green roof with sedum vegetation, grass/herbs vegetation and 15mm for These Blue-Green roof systems could
total-growing- season water the sedum-dominated vegetation. bring significant benefits to UK cities.
shortages can be reduced from 28%
to 4% by increasing the amount of
water stored in the drainage layer
from 0 to 80mm.
During the research period, the
hydrological performance in the sense
of evaporating precipitation water
instead of discharging this water to
For a grass and herb-dominated the sewer was also greatly improved
vegetation, water shortage is by the Blue-Green roof system:
reduced from 29% to 12%. This lesser Total average precipitation water
reduction is caused by the fact that evaporation for sedum increased from
the modelled potential evaporation 290 to 386mm and for the grass/
of a grass/herbs vegetation is higher herbs vegetation from 414 to 515 mm.
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Landscape & Urban Design Issue 35 2019
Not only is a Blue-Green roof intuitive
to install and maintain on a large
enough flat roof area, the spaces
created can offer more benefits for
the end users of the site by increasing
usable green spaces for amenities,
which, in turn, increases biodiversity
and can assist with climate cooling.