Short burn, long heat
Masonry fireplaces are often confused with masonry stoves or masonry heaters – these are not the same thing. A masonry fireplace is simply a traditional wood-burning or natural gas fireplace with a masonry (stone) surround and hearth, and typically a masonry chimney as well. Because of the expense of the stone itself, as well as the expense of the installation by a professional mason, these fireplaces typically start at around $4,000 and can top out at $10,000 to $20,000 depending on size, stone type, and whether or not a full masonry chimney is being installed.
Masonry heaters are a relatively poorly understood piece of home heating technology. Typically massive stone fixtures installed by professional stonemasons, they are referred to variously as "Masonry Stoves", and "Masonry Heaters, with very little division between the two. The main difference between a masonry heater and other types of stoves or fireplaces is in the way that it distributes the heat. Most fireplaces are able to heat your home only while there is a fire burning inside, which means that if you want to stay warm, you'll have to stay busy feeding the fire with wood, or else you'll have to use a gas fireplace, which takes away some self-sufficiency and in some cases leaves you without a heating system in a power outage due to the electrical ignition systems.
Unlike other types of fireplaces and woodstoves , a masonry heater is able to heat your home all day without having to burn wood continuously. The way that it does this is an interesting example of ancient technique meeting with modern engineering to yield an astoundingly simple but effective solution. Since stone stores heat so well and radiate out so slowly, you are able to light a fire in the morning (or evening, or whenever you choose) and build it up, filling the firebox, then simply allow it to burn off over the course of the next few hours. The heat is circulated through the stone, usually by way of baffles or air channels, allowing the bulky stone (often between 2,000 and 3,000 lbs. for a single masonry heater) to absorb the heat from the burned wood and radiate it for 20 or more hours after the fire has gone out, keeping your home warm while you are away at work or simply relaxing in your comfortably warm home. In order to qualify as a masonry heater, the unit must be made mostly of masonry construction, must weigh at least 1,800 lbs. excluding the chimney and masonry heater base, and it must be designed to maintain a surface temperature lower than 110 degrees Fahrenheit in normal burn conditions.
Most masonry heaters are custom-built on site, which allows the installer to ensure that the fireplace is adequately suited to the home it is being installed in. Typically, engineering drawings are required ahead of time, with approval from the local building code officials and your insurance company before installing such a system. Because of the wide variety of materials ranging from granite to marble to soapstone, and the potential expense of shipping and custom work by a professional stonemason, a masonry heater typically costs at least $4,000 to $5,000 more than a simple masonry fireplace (which is to say the price ranges from around $10,000 to $25,000) but is between 5 and 9 times as efficient as a fireplace, as well as offering the flexibility of leaving the heater unattended for up to 24 hours and more. Some manufacturers estimate that a masonry heater will pay itself within around 10 years, but because of the high initial cost, it is typically a combination of lifestyle choice, environmental concerns, and aesthetics which motivate buyers of masonry heaters.