A wood stove of contemporary design by Hwam.
A wood stove, also called a wood-burning stove, is a device that burns wood in order to heat a room and/or, if connected to a boiler, water. Some wood stoves are also equipped to function as an oven. As with any kind of closed stove, the wood stove is much more efficient than an open fire, most of the heat from which escapes up the chimney and is thus wasted. However, the efficiency of wood stoves varies enormously depending on the type and how it is used.
Wood can be economical compared with other fuels, particularly if you have easy access to local supplies. But be aware that different species of wood differ considerably in the amount of heat they give up when burned (see wood heat value) and in other qualities (the burned wood from fruit trees, for example, can be pleasantly aromatic). Also, be sure that the water content of the wood used is not too high (see seasoned wood), as this will make burning difficult and lead to a build-up of creosote in the flue or chimney.
The essential parts of a wood stove are a firebox, or fire chamber, usually made of cast iron or steel and which is more or less air-tight, a grate, and some kind of adjustable air control. Hot combustion gases from the stove are led away to the outside through a flue or chimney.
In choosing a stove, key factors to bear in mind are the quality of construction, the efficiency with which the stove operates under optimal conditions, and ensuring a good match between what heating requirements you have and what the unit can deliver. When it comes to installation, safety and conforming to local building regulations are paramount.
Types of wood stove
The modern wood stove has its roots in the Franklin stove, developed, as the name suggests, by the American inventor and statesman, Benjamin Franklin (1706–90). Over the years, great improvements have been made to the efficiency, effectiveness, and cleanliness of wood stoves. Wood stoves built today are relatively clean-burning, can be highly efficient, and may be sited as little as 20 cm (8 inches) away from the nearest wall. They may be catalytic or non-catalytic.
The simplest kind of wood stove is the free-standing, windowless box stove which sits, with or without legs, on the floor of a room some distance away from a wall. Another basic kind of wood stove, popular in the past for heating everything from schoolrooms to station waiting-rooms but also much used in the home, is the potbelly stove, so named because of its bulging shape. Small, simple stoves such as the potbelly have efficiencies typically in the 25–45%, depending on their age and construction.
Most modern wood stoves tend to be of the slow combustion type, incorporating an airtight firebox, multiple airflow controls and air inlets, and secondary combustion chambers to improve efficiency. They may also be be fitted with a fan to help move heat more evenly around the room. Depending on the model and the way it is run, efficiencies can run as high as 70 or 75%. Even more efficient, but possibly more expensive to run depending on your circumstances, are pellet stoves.
The bottom line is that there's now available on the market almost every kind of wood stove imaginable, from traditional to contemporary design, with or without glass panels to make the fire visible, and incorporating all manner of shapes, sizes, and features. In short there is a wood stove to suit every taste, need, and application.
Features and what to look for
You can tell if a wood stove is well-made by checking for clean castings, smooth welds, tight doors, smoothly-operating draft controls, and the appearance of good workmanship. Most stoves also have firebricks or metal plates to prevent burnout. These materials increase both the life of the stove and, to some extent, the thermal mass (the heat's storage medium). After the fire is out, a 500-pound stove radiates heat several hours longer than a 250-pound stove. Stoves may have doors on the top, on the side, or both.
Many of the new wood stoves have large glass doors on the side so that you can see the flames. Some glass doors perform better than others. For example, one type uses an infrared barrier in the glass that reflects heat back into the firebox. Some new models have airflow systems that remove soot and smoke from the glass doors, making them virtually self-cleaning. Wood stoves can also include several additional features such as thermostats, insulated door handles, removable ash pans and blowers.
If you are purchasing a stove for a home that has never had one, you will probably need to install a chimney. Prefabricated metal chimneys are the easiest types to retrofit. They are relatively inexpensive and not extremely difficult to install. You will, however, need to cut a hole in your roof. If you are using an existing chimney in your house, make sure that the stove you are planning to buy is compatible. Many existing chimneys need to be relined, with stainless steel stove pipe, in order for them to work correctly with the new high-efficiency stoves.