does anyone here have any experience with Empire, (or any other brand) direct vent propane heaters, like the DV-35? I'm not talking about the high efficiency models, like the Rinnai or others like them, as they require electricity, and I'm looking at supplemental and also back-up heat as well, in case of power outages. I was thinking about Empires B-vent heaters, ('tho nobody answered my post regarding them) but I have heard they are somewhat wasteful of room heat that escapes up the chimney when the unit is not operating. Thanks for any help, input, or recommendations. tony