Gas heat built for Marlborough's inner-ring St. Louis homes.

Most gas fireplace projects in the Marlborough area run somewhere between $3,500 and $9,000. A direct-vent insert dropped into an existing masonry fireplace with a gas line already nearby sits toward the lower end—common in the older bungalows here that were originally built with wood-burning fireplaces. A new built-in gas fireplace requiring fresh gas line work and venting through an exterior wall runs higher. Given how many Marlborough homes were built in the same postwar era with similar floor plans, a local installer who's worked the neighborhood can usually give you a tight estimate after a quick walkthrough.

Yes, and it's one of the most common projects in this part of St. Louis County. Many Marlborough homes still have their original masonry wood fireplace, which is now used rarely—or not at all—because of tight lot clearances and limited firewood storage. A gas insert uses that existing chimney as the venting path with a stainless liner, typically running $3,500 to $7,000 depending on the insert and whether new gas line work is needed. It keeps the look of your original fireplace while giving you real, on-demand heat instead of an opening that just leaks warm air up the flue in winter.

Nearly every home in Marlborough is already connected to the natural gas main, since it's a small, densely built municipality inside St. Louis County rather than a rural service area. That means most gas fireplace installs simply tap into existing service rather than requiring a propane tank setup. Propane is really only a consideration here for a detached structure or an unusual situation without gas service already run to the house—your installer can confirm what's available at your specific address.

Most modern gas fireplaces will, which matters in a St. Louis County winter storm when outages can knock out the furnace along with everything else. Units with IPI (intermittent pilot ignition) run on a battery backup that kicks in automatically when power drops, so the fireplace still lights on demand. Valor's lineup goes a step further—their pilot assembly generates its own electricity through the thermocouple, so there are no batteries to remember at all. Ask your local dealer about the ignition system on any model you're considering if backup heat is a priority.

A gas fireplace is a fully built-in unit framed into a wall—typical for new construction or a remodel where there's no existing masonry opening. A gas insert is sized to slide into an existing fireplace, which describes most of the older openings found in Marlborough's postwar homes. A gas stove is a freestanding cabinet unit that sits out in the room, useful when there's no chimney or fireplace opening to work with at all. For most homeowners here with an original wood-burning fireplace they no longer use, an insert is the natural fit.

Yes—installations require a building permit and separate gas line permit, coordinated through the City of Marlborough building department in conjunction with St. Louis County code requirements. The gas line connection has to be done by a licensed gas-fitter, which is one reason it's worth using a certified hearth dealer rather than a general contractor: they handle the permit, the gas line work, and the venting inspection as one coordinated job instead of leaving you to schedule separate trades.

Vented (direct-vent) units draw combustion air from outside and exhaust it back outside through sealed venting—they're the standard recommendation almost everywhere, including Missouri. Vent-free units burn directly into the room and are legal here, but they come with strict room-size and oxygen-sensor requirements that matter more in Marlborough's smaller, older room layouts than they would in a newer, larger house. Given the modest square footage of most homes in this area, a direct-vent insert is usually the more comfortable, lower-maintenance choice, though a local dealer can walk you through both options for your specific room.

Plan on an annual inspection, ideally in early fall before you start using it regularly. A technician checks the burner, pilot assembly, venting, and gas connections, and cleans the glass and interior—this typically runs $125 to $200 in the St. Louis area. It's a much smaller job than a chimney sweep on a wood-burning system, but it's not one to skip, especially on older inserts installed into original 1940s and 1950s masonry fireplaces where venting conditions can vary from house to house.

Gas delivers real heat output and a genuine flame, and it's a natural fit here since most homes already have gas service and, often, an existing fireplace opening to convert. Electric fireplaces skip the venting and gas line entirely—they plug into a standard outlet, cost far less to install, and work in rooms without any existing chimney, which suits an addition or a room where running gas line isn't practical. On the utility side, Union Electric's residential rate runs around 12.6 cents per kWh, which keeps electric units cheap to run for ambiance but not especially efficient as a primary heat source compared to gas. For most Marlborough homes with an existing fireplace and gas already on site, gas remains the stronger long-term choice; electric works well as a secondary or supplemental unit in another room.

Open fireplaces suck—literally. As the fire burns, it consumes air your furnace already paid to heat and pulls it out through the chimney, so the house is actually colder after the fire goes out than before you lit it. An insert fixes this: it seals the chimney, puts fixed glass across the front, and turns that hole in your house into a real heat source.

An insert does two things: it seals the chimney completely, so you stop losing air you already paid to heat, and it radiates warmth into the room through the firebox and glass. Most add a heat-exchange fan that pulls cool room air underneath, wraps it around the hot firebox, and pushes it back out warm. Your home is more efficient before you've even lit the first fire.

Yes—by creating a comfort zone. A furnace heats every square foot of the house just to warm the one room you're in; a gas fireplace on low burns roughly a sixth of the gas a typical furnace does. Set the furnace around 55–60 degrees as a baseline, then heat the rooms your family actually uses. Families who heat this way commonly save $20–$60 a month.

For an average home—covering the fireplace, the vent pipe, and basic installation—a budget between $3,900 and $5,500 gives you a lot of options across wood, gas, and pellet. By the time you add finish work, gas line, and electrical, the average complete installation lands between $5,000 and $12,000 all-in. In a remodel or new build, a good rule is to put about 2.5% of the total project cost toward the fireplace.