Abstract: A gas-burning heater or fireplace insert including a plurality of tiered artificial logs with gas burners disposed strategically between the tiers. The burners at each tier are selected to provide a particular flame pattern, with one or more of the flame patterns being developed in combination with one or more of the logs to promote the generation of localized heat that enhances the visual appearance of the flames of the pattern and increases the heat radiated outwardly of the insert and into the ambient environment. In a preferred embodiment, the insert is capable of operating in a non-vented environment. A method for operating a gas-burning heater or fireplace insert is disclosed as are various unique aspects of the invention including subassemblies of the insert.