Vented Gas Heater

My house has two heat pumps. They work well most of time time, but when the temperature drops below 32, they're not so good. I have a wall-mounted propane heater on the wall in my bedroom. We never run it when we're asleep. It is only used for supplemental heat during the evening before bedtime.
I'd like to have a wall-mounted vented heater that can be run while we're asleep. Since the only place to mount it is on an inside wall, how are these heaters vented? Do they require a hose being run from a port on the heater to the outside of the house? The attic is just a few feet above the heater. It would not be that hard to run some sort of vent through the inside wall and into the unfloored attic space.
What brands or models can you recommend for a bedroom?

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