General rule of thumb, if you are comfortable then the birds will be too.
As long as there aren't cold drafts directly on the bird they can usually stand lower temps some down into the 40's with out too much worry. So if you are one that turns the heat down to 60 at night as long as the house cools off slowly then you won't need to worry about an extra heat source for your bird. Its sudden change that causes the problem.
From personal experience I know that these little quakers are tough little critters. I have an outdoor aviary and the birds can choose to be inside or outside. Last winter in the coldest part of our winter which it got down to about -15 for a few days, they did just fine and continued to go outside. I did however have a heat lamp available to them inside their building so it kept the temp at about 40 at night.
As I said, general rule of thumb, if you're comfortable then they will be too. If you notice that your bird is sitting still a lot and fluffed up but normal in every other way, then its possible that he might be on the chilly side, in which case you can try covering his cage partially and giving him a corner that is protected that he can snuggle in.
I live in an old house where there are cold spots...I don't have central air. Since I have one bird that's fairly naked I use him as a thermometer

If I notice that he has what feathers he has left fluffed up then I know I need to turn the heat up a bit, But I've only had to take extreme measures once with him and that was only because the power went out...