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The reverse-process indoor wood burning stove is a non-catalytic airtight heater. Employing a unique reverse process whereby it not only draws warmed exterior air in to the wood stove for combustion, thus eliminating interior drafts, it also releases fresh outside air through a rear-mounted plenum, where it is heated before entering the premises. This initiates a healthy fresh air exchange system, by introducing oxygen-rich air in to the building. The innovation by Jan Steen started as the Chinook, but later became known as the Sunrise wood stove.

Overview
The reverse-process stove is a wood-burning stove based on two simple principles. One: It draws in fresh, cooler air from outside the building, then sends that air through interior steel pipes, before releasing it near the rear of the stove for combustion. This prevents cold air being drawn in to the premises. Two: Additional exterior drawn cold, fresh air is released to flow gently up the stove's outside rear plenum, where it is heated and released in to the room at the top of the plenum. This now hot, moist, oxygen-rich air creates a slight positive air pressure within the building. Since this positive air pressure is minimal, there is need for a corresponding exit somewhere up high in the building, to allow the subtle air pressure differential to continue. This double effect, i.e. drawing air for combustion from the exterior as well as introducing fresh air in to the dwelling, makes this unit the 'reverse-process' wood-burning stove. Present day wood heating stoves are "95% more efficient than in earlier times" according to Carol Forsloff.

Additionally, the stove's very large cast iron baffle, when closed, forces the combustion gasses up to the bottom of the baffle, where (temperature allowing) they hopefully ignite. Remnant gasses and air then travel forwards and over the opening at the front of the baffle to be finally released up the rear positioned chimney/pipe.

It must be understood that the potential British thermal unit (BTU) output allowed by wood-fuel comes mainly from its inherent combustible gasses which are released upon heating. About 70% of these potential heat-releasing BTUs are created by these gasses upon combustion. Many stoves' temperatures do not reach the required 700 plus degrees Fahrenheit to allow these volatile gasses to combust within the confines of the stove. For wood to become optimum fuel, it must have as little moisture content as possible. Differing wood types, i.e. the faster growing, Softwood trees such as cedar and alder, will at best have half the potential BTUs, when compared to the harder, denser growing trees, such as fir and oak, etc.

Additional features, such as a water jacket, can be installed inside the stove. Although the most solid are cast-iron, experience teaches that water heated through a copper coil is better on the skin. Iron in the water makes a skin quite itchy from the build up of iron bacteria. However, it must be realized that anything that hinders the process of combustion, by drawing away degrees of heat from the chamber, interferes with the potential of complete combustion.

History
Jan Steen is the innovator of the Chinook (later named 'Sunrise') reverse-process wood burning stove. After settling on an island in the Salish Sea on British Columbia's west coast in 1976, the Franklin stove installed in the rented farm house was far from satisfactory. Air leakage through badly fitting doors, a broad and narrow depth combustion chamber and an insatiable need for small pieces of wood because of its short, uncontrolled burns, led Jan to begin his experiments towards the creation of a more efficient vehicle. After 12 prototype models and refining the double airflow configuration, the reverse-process wood-burning stove was born as a far more efficient, time saving, low-tech device. Sadly, with the need for his own foundry, and the industry's costly new safety requirements, the stove never went in to production. The Sunrise 'reverse-process Stove' is a non-catalytic stove which, as a forerunner to the re-introduction of Wood-burning Stoves in the late seventies, was never certified by the United States, or Canada. It was an improvement, created by an entrepreneur at the time. Steen managed to deliver some 75 stoves across Canada with several ending up in Oregon.

Design
With its large firebox design, and extended cast-iron baffle, this barrel shaped stove works as a highly efficient heat producer. However, its uniqueness continues to lie in its reverse-process air flow of releasing hot, moist oxygen air in to the house. Baffles radiate wood gasses back into the heat, allowing for a more complete, secondary combustion. Additionally, the preheated fresh air supply helps keep the primary and secondary combustion temperatures high. As Matthew Stein notes, "the most efficient wood stoves allow for ducting the air intake to draw air directly from outside your home." Open fireplaces are essentially totally in-efficient. While they do radiate heat, giving a sense of immediate comfort to those sitting in front of it, the fact they draw air directly from the room, sending hot air up the chimney, ultimately results in lowering the overall temperature of the premises. This can be verified by reading a temperature gauge located away from the fireplace.

Safety
Any indoor closed heating appliance used to heat up a building requires the oxygen in fresh air for burning the wood. Upon combustion there is an output of carbon monoxide (CO). Carbon monoxide is a poisonous, odorless gas which exits via the chimney. During the cold winter months, wood stoves are employed for heat. In the 1970s building codes were adopted introducing new construction standards. These required tighter sealed windows and doors, and plastic vapor barriers in walls and ceilings. While this created a tighter sealed barrier to the exterior of the building, it stopped fresh air from entering. This increased the build up of indoor pollution by creating stale air. That in turn led to condensation, with the result of the formation of highly toxic molds and mildews. So with all good intentions, while improving in one area, it created problems in an other.

A wood stove employing indoor air for combustion creates problems, since cold air is sucked in to the premise, while on its way to the stove to ultimately disappear up the chimney. The reverse process wood burning stove provides a means of fresh warm air entering the home, rather than creating constant drafts of cold air being drawn in from small openings around windows and doors. By releasing fresh air into the room, the building breathes outwards rather inwards, allowing for a slight positive pressure to build up inside.

A passive solar building design maximizes heating efficiency and due to its tight heat conserving principles and seals must consider adequate air exchange. The building codes for solar homes necessitate a back up heating system. In this regards the highly insulated solar home will also benefit from preheated fresh air entering the home from a back up wood burning stove such as the reverse-process stove.

The National Building Code of Canada mandates new sealed air tight homes with improved air and vapour barriers including a ventilation system which can replace one third of the volume of interior air each hour. Similarly, the American Society of Heating, Refrigerating and Air Conditioning Engineers, recommend that air in a dwelling should be replaced totally every three hours. Fresh air intake is needed to reduce the dangers of indoor pollutants such as particle board formaldehyde releases and radon gas infiltration. With a reverse-process wood burning stove, or fireplace, fresh air is drawn into the home directly, eliminating cold air draft while conserving costs by creating heating efficiency. A reverse-process stove reduces indoor air pollution with its constant intake of fresh air from outdoors.