Helimutt, you would find the same problem on anyone's -400s, so perhaps you'd better go caravanning or boating at home next year
I haven't personally found that to be the case.
Why do you need air conditioning when the air is -35C outside? Isn't all the fresh air being filtered into the cabin being compressed and heated first? Surely it just needs to be heated less, not actively cooled.
I find one of the major contributors to the problem to be when an aircraft hasn't been configured with the over-seat air vents. The first thing I do when I get to my seat is reach up and open the air fully and adjust the direction. If I don't have that I find it gets intolerably hot and stuffy very quickly.