376
M. Fiori et al.
Nevertheless, climate change is threatening the efficiency of these alternatives,
given the strong heat stress, the large amplitude of the temperature variation to
which the vegetation is exposed, and/or the increase of water vapor and decrease
of liquid water in warm seasons (i.e., higher air’s water vapor carrying capacity)
(Wong et al. 2012). In consequence, some vegetation might not withstand the climate
variations undergone at their location, modifying the thermal properties of the green
roof (Paolini 2015). Fiori et al. (2013) and Simmons et al. (2008) have studied
green roof performance for different green roof types, obtaining significant variance
according to the combinations of soil, vegetation, and irrigation. Simmons et al.
(2008) explored the variance of green roof maximum runoff retention and thermal
properties at different water contents, for different green roofs’ layer composition.
Farrell et al. (2012) studied the survival of green roofs’ vegetation when subjected
to drought, testing their tolerance to limited irrigation, highlighting the importance
of proper selection of the type of vegetation according to the climate.
Environmental alterations have been witnessed during the last five years (Wong
et al. 2012); thus the way the green roof would respond for delivering the desired
heat rejection. The research intends to show how the green roof has adapted to the
variations in the temperature changes along the past decade and how these variances
could be aided by the control of water content delivered to their vegetation and stored
within the soil.
The following study has been presented and developed by SEEDLab.ABC, ABC
Department, and Politecnico di Milano. All data has been surveyed thanks to the sensor installation done by METEOLab.ABC, and the data monitoring is carried out by
SEEDLab.ABC. From the stored data, outdoor temperature, relative humidity (RH),
total solar radiation, surface temperatures, and water content have been inspected for
a green roof of a two-story office building in Milan, Italy (45° 28
47
N; 9° 13
47
E).
The green roof is divided into eight parcels with different vegetation, plus a gravelfilled reference parcel, representing the original finishing of the roof. Each layer
temperature has been surveyed to establish the heat transfer through them. A plan
view of the green roof is shown in Fig. 1. The sensor distribution is described in the
roof slab cross section as shown in Fig. 2. The data collected has been confronted to
see how the local climate variances have affected the heat transfer.
2 Weather and Green Roof Condition Variance
All the data gathered has been condensed into three typical days for summer, midseason, and winter. From the average value encountered for the 24 h of June, March,
and December, this was done for green roof parcels 5 (i.e., vegetation layer as sedum
on moss) and 6 (i.e., vegetation layer as sedum on lapillus), during 2012, 2017, and
2018. Air temperature, relative humidity, and total solar radiation data, gathered from
an on-site weather station, have been screened, together with the surface temperatures. Figure 3a shows how the fluctuation on solar radiation is high for March (i.e.,
~1.5 times higher in 2012 than in 2018), but the air temperatures are approximately
M. Fiori et al.
Nevertheless, climate change is threatening the efficiency of these alternatives,
given the strong heat stress, the large amplitude of the temperature variation to
which the vegetation is exposed, and/or the increase of water vapor and decrease
of liquid water in warm seasons (i.e., higher air’s water vapor carrying capacity)
(Wong et al. 2012). In consequence, some vegetation might not withstand the climate
variations undergone at their location, modifying the thermal properties of the green
roof (Paolini 2015). Fiori et al. (2013) and Simmons et al. (2008) have studied
green roof performance for different green roof types, obtaining significant variance
according to the combinations of soil, vegetation, and irrigation. Simmons et al.
(2008) explored the variance of green roof maximum runoff retention and thermal
properties at different water contents, for different green roofs’ layer composition.
Farrell et al. (2012) studied the survival of green roofs’ vegetation when subjected
to drought, testing their tolerance to limited irrigation, highlighting the importance
of proper selection of the type of vegetation according to the climate.
Environmental alterations have been witnessed during the last five years (Wong
et al. 2012); thus the way the green roof would respond for delivering the desired
heat rejection. The research intends to show how the green roof has adapted to the
variations in the temperature changes along the past decade and how these variances
could be aided by the control of water content delivered to their vegetation and stored
within the soil.
The following study has been presented and developed by SEEDLab.ABC, ABC
Department, and Politecnico di Milano. All data has been surveyed thanks to the sensor installation done by METEOLab.ABC, and the data monitoring is carried out by
SEEDLab.ABC. From the stored data, outdoor temperature, relative humidity (RH),
total solar radiation, surface temperatures, and water content have been inspected for
a green roof of a two-story office building in Milan, Italy (45° 28
47
N; 9° 13
47
E).
The green roof is divided into eight parcels with different vegetation, plus a gravelfilled reference parcel, representing the original finishing of the roof. Each layer
temperature has been surveyed to establish the heat transfer through them. A plan
view of the green roof is shown in Fig. 1. The sensor distribution is described in the
roof slab cross section as shown in Fig. 2. The data collected has been confronted to
see how the local climate variances have affected the heat transfer.
2 Weather and Green Roof Condition Variance
All the data gathered has been condensed into three typical days for summer, midseason, and winter. From the average value encountered for the 24 h of June, March,
and December, this was done for green roof parcels 5 (i.e., vegetation layer as sedum
on moss) and 6 (i.e., vegetation layer as sedum on lapillus), during 2012, 2017, and
2018. Air temperature, relative humidity, and total solar radiation data, gathered from
an on-site weather station, have been screened, together with the surface temperatures. Figure 3a shows how the fluctuation on solar radiation is high for March (i.e.,
~1.5 times higher in 2012 than in 2018), but the air temperatures are approximately