In the case of horizontal cladding, the ventilation is provided between the vertical battening and by means of the notches in the ventilating back wood; ventilation is also possible between the stiles.
Double battening is preferably used for vertical cladding, because a single horizontal beam (without notches) excludes air circulation behind the cladding.
In addition to the double battening, the horizontal beam must be bevelled inwards at the top so moisture is guided away from the cladding.
In all cases, you will have optimum ventilation when using double battening. Sufficient ventilation is an important part of facade quality.