The average temperature of the leafs in one grid box is calculated by solving the energy balance of the leaf surface with respect to the actual meteorological and plant physiological conditions. Turbulent fluxes of heat and vapour are calculated from the given wind field and the geometry of the plant (see next section). The calculation of radiative fluxes include the shading, absorption and shielding of radiation as well as the re-radiation from other plant layers.

The gas and heat exchange between the vegetation and the atmosphere is controlled by the local energy balance steering the leaf temperature and by the stomata conductance controlling the gas exchange (vapour and CO2).
The actual stomata conductance of a plant is a complex function depending on external meteorological conditions (air temperature, available solar radiation PAR and many others) as well as on the plants physiological processes (Photosynthesis rate, CO2 demand, CO2 fixation,…). ENVI-met uses a sophisticated model to simulate the stomata behaviour of the vegetation.
To define the height and the shape of a plant, the model uses standard normalized functions (Leaf area density profile LAD, Root area density profile RAD) which can be applied for grassy surface as well as for huge trees.

Liquid water on the leafs influences highly the evaporation of the plant. The condensation of water of the leafs, the absorption of rain and the transport between different layers or the ground surface due to gravity is treated as an independent system inside the model.