The lines between indoor and outdoor living are becoming increasingly blurred. Case in point: the see-through indoor/outdoor fireplace.

This type of fireplace can be installed in an external wall, connecting an indoor space with a patio, backyard, or deck. A double-sided glass firebox presents intriguing design possibilities — now a flickering fire can frame a view.

If your clients request this feature, there are a few considerations to mull over.

1. Do you have the space to accommodate it?

While models range in size, a two-sided fireplace tends to be a larger than a conventional unit. That’s because, depending on the model, you’re essentially getting two fireplaces — one rated for indoors and one rated for outdoors. Also plan for a panel door to access controls, gas valve, and combustion air ducts.

“A lot of the time, when a client comes to us with an indoor/outdoor fireplace in their plans, we’re going to need about 34–40 inches from door to door, and a lot of the chases are drawn at 24 inches, so that’s either going to add more outside or it’s going to bring the fireplace more inside. So it’s more of a spatial constraint in that regards,” advises Chris Maxson, president of Acucraft, a luxury fireplace manufacturer in Big Lake, Minnesota.

2. Where will you put it?

Another advantage of an indoor/outdoor fireplace is that some models can pull in combustion air from outside. That way, the house isn’t losing any conditioned air up the flue. That’s if you even need a flue. Some models include ventless technology that eliminates the need for an exhaust flue. Still, the unit or its vent cap must be kept a certain distance from doors, windows, overhangs, and other elements of the home. Follow your local code to help determine placement.

3. Which fuel source?

Will the fireplace use wood or gas? Gas fireplaces tend to be more efficient than wood-burning units. And they’re cleaner, too, producing less soot and particulate matter. When natural gas isn’t available — or if your client prefers bigger, slower-moving flames — clean-burning propane is an option. Work closely with your propane supplier or plumbing technician to determine gas line size, not only for the Btus in the fireplace but for all the gas appliances in the house.

“Twenty or 30 percent of our gas customers are building in propane environments, so we spent two years perfecting the propane flame,” Maxson says.

This is the outside view of the same Acucraft fireplace seen in the top photo.

4. What will it look like?

This is where you get to flex your creative muscles. If you plan accordingly, you’ll have plenty of design flexibility:

  • Consider configurations. You could install the indoor/outdoor fireplace flush against the interior wall, with the back portion jutting outward, surrounded by attractive masonry. Or you could split the difference — half in, half out.
  • Elevate it. Install the fireplace several feet above the floor like a window for a contemporary feel.
  • Go open flame. A glassless front, either inside or outside, brings the fire out into the open. Be sure to use a safety screen if you go this route.
  • Bring it inside. Bob Rizzo, president of American Propane in Everett, Massachusetts, recalls a project that made the fire visible from the outside even though the fireplace was completely contained inside. The project called for Rizzo to install a Sky L T fireplace from European Home in a steel frame that aligned with an exterior window. Marble surrounded the see-through fireplace, which was set back from the thermopane window for unobstructed views of the flames inside and out.

A few more pointers

Rizzo has installed a lot of indoor/outdoor fireplaces because of their growing popularity and offers the following tips to help ensure your project goes smoothly:

  • Make sure it’s weather-tight. Leaks are the biggest risk of installing an indoor/outdoor fireplace and are commonly the result of poor workmanship. Work closely with your masonry or siding contractor to ensure the outside fireplace is properly flashed. “Sometimes, you have to go back and review what they didn’t properly seal because there were some leaks inside,” Rizzo cautions.
  • Get all trades aligned. Multiple trades are involved in installing an indoor/outdoor fireplace — a plumber to size and connect the gas line, an electrician to hardwire it, carpenters to frame it, and a fireplace technician to install it. Make sure they’re all working from the same specifications. “If there’s a clash between the architect’s drawing versus the installation manual, that’s to be worked out with the architect,” Rizzo says.
  • Don’t go off book. Stick to the manual. The manual will contain all the critical information to help determine venting clearances, weather-proofing, and other rules to ensure your project passes inspection.

Photos by Acucraft