Funnily enough I asked this very question a while ago over on the 'prune, on the engineering forum. I was assured by those that know, that exit rows indeed ARE colder - the main reason being lack of insulation. Additionally, the door frame reaches to the outer skin and (presumably) conducts some of that extreme cold inwards. And finally, yes, the seals do indeed leak to a small degree and whilst personally I've never felt particularly cold when perched in row 28, it's true there's definitely a bit of extra racket going on. Rather like a car ride where the window's not completely shut.