G r e e n R o o f s a s P a s s i v e C o o l i n g S t r a t e g i e s
593
Table 1: Thermophysical properties of the green roof different layers
Layer
Material
Thermal
conductivity
[W/mk]
Density
[kg/m
3
]
Specific
Heat [J/kgK]
Vegetation and soil
substrate
0,150
Lapillus,
Compost
0,17 (dry)
0,33
(saturated)
582
1000
Filter sheet
0,001
Polypropylene
0,220
910
1900
Drainage, storage
and ventilation
element
0,002
Polyethylene
0,380
950
2300
Air (inside the
drainage element)
0,023
Air
Thermal Resistance = 0,16 W/m
2
*K
Retention Felt
0,004
Polypropylene
0,220
910
1900
Roof covering
0,001
Copper
380
8900
382
Osb board
0,015
OSB
0,130
630
2200
Insulation
0,120
EPS
0,035
25
1470
Roof Slab
0,050
Fir wood
0,120
550
2700
An automatic drip irrigation system was installed on the green roof in the summer
season that automatically turned on at 6 a.m. every morning for one hour.
External weather conditions were recorded every 10 minutes throughout summer 2010
by means of a 12-bit datalogger (Elog Lsi-Lastem) to which instruments were connected
in order to measure global radiation (DPA 153 Lsi-Lastem), temperature and relative
humidity of the air outside (DMA 572.1 Lsi-Lastem), speed and wind direction (DNA 021-
024-027 Lsi-Lastem), and rainfall (DQA030 Lsi-Lastem). Thermal data on different
stratigraphies (Fig. 5) were also observed in the same period by means of 5 12-bit
dataloggers (Elog LSI-Lastem) connected to:
- thermal resistances (PT100 Lsi-Lastem) for measuring internal surfaces temperatures
(soffit of roofs slabs and walls);
- thermal resistances (PT100 Lsi-Lastem) for measuring temperatures within the different
layers of the roof coverings (surface of the insulation, surface of the covering, ground, air
cavities);
- air temperature and RH probes (DMA 572.1 Lsi-Lastem) for measuring temperature
and humidity of ventilated roofs air cavities and inside the building;
- probe for measuring temperature and moisture content in the planted roof soil
(DISACC4825 Lsi-Lastem);
- heat flow meters (HFP01 Hukseflux) for measuring heat flux entering the roof slabs
(only roof types 1, 2,4,7).
The accuracy of the probes is +/-0,15°C for thermal resistances and +/-5% for heat flow
meters.
