The subject of the invention is an electrically controllable device having variable
optical and/or energy properties of the electrochromic type, which comprises a
functional film consisting of a layer or a stack of layers which is placed between
two external substrates which meet the following criteria:
##CHR1##
at least one is essentially transparent;
##CHR2##
at least one is based on one (or more) film(s) based on one
or more polymers;
##CHR3##
each of them is a water vapor barrier, with a water vapor permeability
of at most 1 g/m2/24 h, especially at most 0.1 g/m2/24 h.
