As long as indoor temps are 55 deg F or above, it should be fine. You can also provide "local heat" with heat mats.
For the plant that doesn't want to go to sleep, push it... stop watering completely. (It's time to do that anyway) Some people trim the leaves, which also pushes it into dormancy. I don't, just stop watering and ignore.
For your orchids in general, consider a space heater like this:
SALE - Bio Green Palma 120v Stainless Steel Waterproof Greenhouse Heater It has a fan that runs all the time, creating gentle air movement. I just got one, and it seems quite efficient. Ops, they seem to be out of stock. Actually, for indoors, any old space heater will do, just be careful to keep dry.