AFAIK the best-practice for applying insulation+vapour barrier in cold climates is:
inside -> inside wall -> vapour barrior -> insulation -> outside wall (exposed to the elements).
If you put the vapour barrier between the insulation and the outside wall, you could risk vapour reaching the outside wall resulting in condensation and mold.
Why am I then, here in my cold climate country, seeing a lot of new buildings with insulation boards with foil facing outside?
The foil is probably there to give radiant insulating properties, but it's also a vapour barrier.
Could it be that there's also foil facing the inside and thereby eliminating the condensation issues?