Linear Fireplaces

It depends entirely on the fuel, and getting this wrong is expensive. Electric, ethanol and water vapor models burn nothing that needs venting, so they need no flue at all. Gas is where it splits: most of the gas models here are vent-free, but a number are direct vent and a couple are vented, and those need a vent run designed into the wall before the framing goes up. Check the venting type on the individual product page rather than assuming the category.

Indoors, yes, within limits. An electric fireplace heats with a fan-forced coil, which warms the air, and most models here are rated as supplemental heat for a single room rather than as a primary heat source. Outdoors it is a different story: warmed air drifts away the moment there is any breeze, so an outdoor electric fireplace is bought for the look. If you want people to feel warm on a patio, pair it with an infrared patio heater.

Proportion, and everything that follows from it. A traditional firebox is roughly as tall as it is wide, so it reads as a hearth you gather around. A linear unit is typically two to three times wider than it is tall, so the flame becomes a horizontal line and the fireplace behaves like a design element in the wall. That shape is also why linear models suit a media wall, where the fireplace sits below a screen rather than competing with it.

Yes, if you choose a see-through or three-sided model. A see-through unit passes through the wall and shows the same flame on both faces, which suits a fireplace between a living room and a dining room. Three-sided models turn a corner or sit at the end of a peninsula. The choice has to be made before framing, because the rough opening and the finish are different for each.

Compare the unit's depth against the stud wall you have. A 2x4 wall gives about 3.5 inches of usable depth and a 2x6 gives about 5.5 inches, so slim electric models often recess into an existing wall while deeper units need a furred-out wall or a chase built for them. Gas direct vent models are the deepest of all, commonly well past what any stud wall offers, so they are framed into a purpose-built enclosure.

Start with what the room can give you. Electric needs only a circuit and installs almost anywhere, which is why it dominates media walls and retrofits. Gas gives you a real flame and real heat but needs a gas line, and possibly a vent run. Ethanol also gives a real flame with no gas line and no flue, though it is refuelled by hand. Water vapor produces a flame effect from mist and light with no combustion at all, which suits places where a real flame is not allowed.