Gas fireplaces may be vented or unvented and outfitted with either concrete or ceramic inserts designed to resemble real wooden logs. Some areas, such as the state of Minnesota and all Canadian provinces and territories, do not permit the use of vent-free appliances. In these locales, concrete or ceramic log sets may only be used in vented, wood-burning fireplaces with open glass doors and a fully engaged damper. Where allowed, ventless log sets may be placed in approved, closed-dampered enclosures that allow adequate combustion and ventilation.
Vented Gas Logs
A vented gas log set vents the gas fumes up a chimney. The flames are larger because more British Thermal Units (BTUs) of gas are used. If heating your interior space is a priority, vented gas logs are less efficient than their ventless counterparts because most of the heat rises up the stack. In vented applications, ceramic fiber logs produce a glowing effect that captures twice the radiant heat of concrete sets, thereby increasing heating efficiency in your interior space.
Vent-Free Gas Logs
Vent-free gas logs require about half the fuel as vented installations because they are operable with the damper closed and the glass doors open. This system burns less gas and captures more heat. Concrete refractory logs do not produce the glow of ceramic logs but may be preferred in vent-free installations because their intricate, detailed designs more closely resemble a stack of real fireplace wood. Concrete logs are also heavier and can be more durable than ceramic fiber logs.
Other Considerations: Ceramic Fiber Logs
After about 15 minutes burning time, ceramic fiber logs produce a realistic glow that mimics the coals produced in a wood- burning fire. Vented or ventless, ceramic logs have a visually pleasing appearance when your fireplace is in operation. Ceramic fiber tolerates the extreme temperature variances caused by frequently turning the fire on and off. Resultant combustion cleanliness decreases the frequency of problematic clogged burners that reduce proper combustion and fireplace efficiency.
Other Considerations: Concrete Logs
Concrete logs weigh 75 percent more than ceramic fiber logs of the same dimensions. If moving and lifting heavy objects is a concern, a ceramic log set may be preferred. If realism trumps weight considerations, concrete logs are the way to go. Look for sets that are highly detailed and feature the look of charred edges and wood grain color and texture. In all things, you get what you pay for. Compare price, look and installation type to make your own informed decision.