Pets, like humans, need sufficient heating when it gets cold outside. However, they have completely different requirements.
Before you think about cranking the heat, take these tips into consideration:
Age
For younger cats or dogs, their bodies aren't fully developed yet. That said, they don't have enough (or thick enough) fur to keep them warm.
Keeping this in mind, make sure to keep the temperature to where they're not constantly cold. If you see them shivering, crank up the heat.
Type of Animal
For cats, all they need to keep warm is a nice place to sleep. From there, their bodies will regulate temperature to keep them nice and toasty.
Dogs are a bit different. Depending on their fur type, you might need to keep the temperature in a higher range. Having said that, make sure your heater is properly installed.
Breed
Of course, Sphinx cats will need more heat as they don't have fur. The same goes for dogs with a less amount of fur.
Again, depending on your animal, keep a close eye on how they react in their environment. Just because you're warm doesn't mean they are.