Free-standing stoves, ovens, and fireplaces are generally not the most efficient forms of home heating and it is generally not advisable to have any forms of open combustion indoors. But these devices are often chosen for their aesthetic aspects or their potential for energy independence and have greatly improved in recent decades thanks to both modern technology and a freer flow of intercultural knowledge. For small structures, such as cabins, they can be a very practical choice and modern forms can sometimes be much cleaner, safer, and well suited to DIY installation. The Utilihab components catalog does not offer any specific kits for this form of heating but it can readily use lighter forms of them in most structures with the combination of adapted panels modified to accommodate their exhaust chimneys and need for heat/flame-resistant bases. There are several basic forms;

•Stoves: Free-standing enclosed metal fire containers that are powered by wood, wood pellets, gas, and other similar fuels. Once commonly used coal fuel, but this has become generally obsolete. Usually made of cast iron or a combination of cast iron and folded steel. There are countless designs but most are variations on the Franklin Stove, the ‘potbelly’ stove, cylinder stoves, box stoves. Pellet and gas stoves are generally the most efficient and modern pellet stoves often feature automated feed. A recent innovation in these has been the somewhat experimental (though there are off-the-shelf products) integration of IR photovoltaic cells into pellet stoves as a supplementary source of electricity.

•Kachelofen and other masonry stoves: A traditional form common to Europe which employs ceramics rather than metal enclosures and sometimes internal flue channels. Often more efficient and cleaner than metal stoves with a slower and longer radiant heat output. Contemporary forms employ modular assembly that make them easy for DIY installation and aesthetically complimentary to modernist homes. Some can integrate water heaters for integration into a central heating system or to supplement solar heating. Another recent innovation in this form from the 1980s is the Rocket Stove; a very high-efficiency masonry stove that employs insulation to maintain high flue temperatures and thus efficient combustion, resulting in much reduced smoke and fuel consumption. Intended to improve lives in the developing world, it has become popular among DIY home builders employing cob and adobe construction as it is simple and more reliable than previous DIY stove designs. However, few modular designs have been devised as these have typically been scratch-built from found materials and often integrated into a cob or adobe building.

•Spirit Fireplaces: Increasingly popular with new-Modernist interior designers, spirit fireplaces are purely ornamental fireplaces powered by smokeless plant-derived alcohol. They generate little to no usable heat but this also allows them to operate without chimneys and be packaged into compact self-contained often portable units that, in some case, can be built into or hung on the wall like a piece of art.

•Outdoor Furnaces: Self-contained wood, pellet, and other bio-fuel furnaces that function as free-standing units with integral weather enclosure. These are designed to function as a boiler/water heater in an otherwise conventional hydronic heating system. Most employ some kind of automated fuel feed. This is probably the most efficient and safest way to use biofuels in a domestic heating system but the units tend to be large, industrial-looking, and, of course, have the maintenance overhead of any device burning solid materials for fuel. One very small variation on the concept of the outdoor furnace is the Japanese Chofu Heater; a quite small outdoor furnace shaped like a cylindrical wood stove but designed to heat water, usually for an outdoor ofuro bath or hot tub.

[Need to consider Tigchel heater stackable modular masonry heaters as possible standard form.]