Solar radiation and Green Roofs
Relationship between:
solar radiation and conventional roofs
On conventional roofs, the solar energy absorbed is essentially released as Sensible Heat and Thermal Radiation.
The large percentage of sensible heat causes a considerable rise in temperature and negatively impacts the tolerability of the surrounding microclimate.
Relationship between: solar radiation and Green Roofs
On a green roof, on the other hand, a considerable fraction of energy is stored by the newly created substrate (new soil) and then used by the plants to evaporate water using Latent Heat (evapotranspiration).
The Albedo * of a green roof is much higher than that of a conventional surface (roof) (0.7/0.85 compared to 0.1/0.2); this results in a higher reflection (from 20% to 30%) of short-wave solar radiation (Berardi et al. 2014).
Up to 60% of net solar radiation is absorbed and used for Chlorophyll Photosynthesis and Evapotranspiration, reducing Latent Heat (Schmidt 2010; Takebayashi & Moriyama 2007; Berardi et al. 2014).
The result is a lower percentage of Thermal Radiation and Sensible Heat released into the surrounding environment.
*Coefficient of reflection of wave or corpuscular radiation by a surface.
