Dogs have very 'sturdy' vascular systems, much like horses. My basenji has very fine hair (even bald patches in some areas), but even so we often go for hour long walks in -10 or lower degree temperatures with little issue. Of course, that's with him running around. Still, if a human is capable of living in a 50 degree F environment, a dog can do that easily, even if they're at rest in a crate.
We had to live for months in a low heat environment (negative degree temperatures outside) when our heater system went kaput. Dogs never had a problem. I'd say exceptions might be necessary for a dog on the older side, but that's just my personal opinion (with little factual basis to go off of.) They do love their little special heat spots, but dogs don't really need a whole lot, even if we're more than happy to give it to them.