Fireplace Inserts

What an insert is for

An insert goes into an opening that already exists, most often a masonry fireplace that is no longer used or no longer efficient. Rather than rebuilding the fireplace, the insert fills it with a modern sealed appliance and the original surround stays.

That is the whole appeal: the opening, the hearth and the mantel are already there, and the work is contained within them. It is a different proposition from building a fireplace into a wall that has none.

Direct vent gas inserts

The gas units here are direct vent natural gas appliances with electronic ignition, which means they light on demand, rather than keeping a standing pilot flame burning between uses. Direct vent means the unit is sealed from the room: it draws its combustion air from outside and sends its exhaust out through the same concentric flue, so no room air goes up the chimney.

That sealed arrangement is what makes a gas insert efficient compared with an open fire, which loses heated room air up the flue continuously. It also means the installation involves a liner run through the existing chimney and a gas supply brought to the opening, both of which are work for a qualified installer and are governed by local rules, not by anything on this page.

Electric inserts

The electric units are a different category entirely. They produce a flame effect with light instead of combustion, heat with an element, and run from an ordinary outlet, which means no flue, no gas and no combustion air.

Several here are infrared quartz heaters with a log or brick effect behind the glass. Because nothing burns, an electric insert can go into an opening that has no chimney at all, including a decorative fireplace that was never meant to be used.

Which one a project needs

The question is usually settled by the building rather than by preference. If there is a working chimney and a gas supply nearby, a gas insert turns an unused fireplace into a genuine heat source. If there is no flue, no gas, or the fireplace is sealed off, an electric insert is what will physically work.

Cost and disruption follow the same line. A gas installation involves a liner, a gas connection and a qualified fitter; an electric one involves an outlet. The electric fireplaces page covers the wider electric range, including units for walls with no opening at all.

Sizing an insert to an opening

An insert has to fit the firebox it goes into, and the published dimensions of the unit are only half of that: the opening has to accommodate the body, and on a gas unit the flue has to run up the existing chimney.

The gas units here are listed at 28 inches, and each unit publishes its own dimensions. Measuring the opening at the front, at the back and at the top, since masonry fireboxes usually narrow toward the rear, is what tells you which ones are candidates.

What stays and what changes

In both cases the surround, the hearth and the mantel stay where they are, which is the reason most people choose an insert over rebuilding. If the surround itself is being replaced at the same time, the marble fireplace surrounds range covers carved stone pieces.

What does change is the face of the fireplace: an insert brings its own frame and glass, and that becomes the visible element within the original opening.