Fireplaces were the most common means by which a house, castle, or any type of building were heated in past times.  The means of temperature control simply involves moving closer to the fireplace, the source of heat.  The method by which the heat is increased is again very rudimentary by increasing or decreasing the amount of firewood in the fireplace.  Over the years however, their role as the most dependable form of heat, has diminished. 

Fireplaces are not used for their efficiency, since far more effective means of heating exist today.  Their role has developed from that of an effective heat source to that of an aesthetic purpose.  As fireplaces have continued to develop over the years, their components, fuel types, and function have also dramatically changed.  Today, gas fireplaces have become a common component of the modern house’s living room or ‘great’ room.  Instead of dragging wood fuel across the living room, gas fireplaces can be enjoyed at the convenience of a remote control. 

     Rumford Wood Fireplace

For a wood fireplace the core components include a

1. Damper
2. Throat
3. Chimney
4. Smoke Chamber
5. Firebox
6. Hearth
7. Cap
8. Flue

In a gas fireplace, the same components can be used although this is not necessary.  A gas fireplace is an enclosed unit, often behind glass, whereby the gases from the flame never have the opportunity to escape into the room and are forced out by the exhaust fan.

Typical Wood Fireplace        Typical Gas Fireplace

related link: Gas Fire Place

Either segmented or single throats can be used as shown below.

Segmented                                                         Single 

Our class defined a system to be “an organized set of related components working together to produce a desired result.”  Regardless of the type of fireplace, the definition of a system is met when the subsystems work together and function as a complete system.  The components, previously mentioned, cannot function individually but must function collectively in order to produce their desired result.  The desired result, creating heat, is met when all subsystems work together.

If the damper would fail, for example, the entire fireplace would fail since all subsystems are interrelated and therefore interdependent. 

          The uses of fireplaces have changed and developed over the years, from being a crucial part of sustaining life, to becoming simply an ornament.  While fireplaces undoubtedly still provide heat, their uses have been limited to purely the aesthetic when economical factors are considered.  In past times they were used as the main source of heat, thereby providing several uses.  These included but were not limited to cooking, metal working, drying of clothing, and heating the house. 

            Fireplaces are limited in several arenas.  The location in the typical house, confines the heat source to one region of the house, leaving hot and cold pockets throughout.  Although gas fireplaces can be powered by a remote control, and have no cleanup, wood fireplaces, require significant effort in starting the fire, and significant time in cleaning up the debris and by products of the fire.  When compared to other sources of heat in the modern home, fireplaces once again pale, yet their aesthetic features keep them alive. 

        The materials used within a fireplace must most definitely be of a non combustible nature.  When gas fireplace’s are constructed, the materials used are simply a light-gauge steel for the casing, a gas line, and a glass front plate.  Electronic components such as a fan can be added, but most of the materials used are simply steel and glass.  In a wood fireplace, the firebox is often constructed of any of several types of masonry.  This includes soapstone which is a very good retainer of heat, which continues to radiate heat long after the fire goes out.  The dampers, and flue are constructed of a light-gauge steel, while wrought iron is used as a form of decoration around the hearth.

Materials and typical sizes

The numeric parameters on various sizes for gas and wood fireplaces are listed below.  Efficiency ratings for a fireplace range from negative to a positive 40%.  Negative efficiency exists in old fireplaces where cold air is absorbed into the building through the chimney and although the fireplace warms its immediate vicinity, the building overall cools down. 

 http://www.rumford.com/segflyerplan.gif picture source.

Btu output for a typical gas fireplace is in the range of 17,000 BTU/hr., while its maximum area of heat is 1,050 ft. squared.

Wood Burning System

Above parameters compare selected types of wood burning fireplaces.  Masonry and zero clearance systems vary in heating capacity, but maximum energy they delivered is about 70, 000 Btu/hr.  The efficiency achieved is about 70% and it can be accomplished with different sizes of units.

Gas Burning System

Above parameters show zero clearance gas burning system having lower variable input and heating capacity than wood burning system.  However, the steady state efficiency of gas burning system is about 10% higher than wood burning systems.   Major advantage of this system is that heat is produced even when the power is out.  

Source: HVAC SYSTEMS

Heat Output numbers are based on a home with 8' ceilings, R-28 insulation in the walls, R-42 insulation in the ceiling, and located in Northern climate. 

Source: Fire Place

Radiative heat pattern from a typical fireplace       

Gas flow through a fireplace throat

Masonry System:

1. 8" of solid masonry  must separate  a fireplace from a combustible material

2. system has to be constructed on heavy footing to support the system's heavy weight

Zero Clearance System:

1. system has to be constructed on double floor joists 

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