Fireplaces are not only an aesthetic element of the interior, but above all an efficient source of heating. In order to achieve optimum performance and safe operation, it is essential to choose the right stove model to meet the thermal needs of the building and to correctly size the chimney to ensure safe flue gas removal.
Choosing the right wood burning stove
There are several key factors to consider when choosing a wood stove. The performance of the stove should be adapted to the size and heat loss of the space to be heated. Stoves that are too powerful can lead to overheating, excessive tarring and flue gas deposits, while undersized stoves will be operationally inefficient and excessive loading will reduce their lifetime.
It is also important to take into account the mentioned heat loss of the building. Older stone houses have different heat loss values than modern timber buildings. When calculating the required performance of the stove, the so-called stove constant is used, which distinguishes several categories of buildings. Very well insulated buildings, such as passive houses or timber-framed houses, have an average heat loss of around 12 Wh/m³. Well-insulated buildings, such as modern brick houses, are around 22.5 Wh/m³. Moderately insulated buildings, such as those built in the 1990s, show values of around 32.5 Wh/m³, while poorly insulated buildings, i.e. historic buildings without insulation, can reach up to 45 Wh/m³.
The stove constant is calculated in the Czech Republic with the assumption of an outdoor temperature of -15 °C and an indoor temperature of 20 °C. Since winters have been warmer in recent years and the outdoor air temperature has only rarely dropped to -15 °C, it is possible to calculate values up to half of this for buildings intended for permanent housing where stoves and fireplace inserts are used for reheating.
Fuel
The type of fuel is also an important factor when choosing stoves and fireplace inserts, depending on the user's preferences and the availability of materials.
Wood is affordable but requires proper drying and storage. Hardwoods, such as oak or beech, burn longer and more evenly, while softwoods, such as spruce or pine, are more suitable for thawing. The operation of the stove also plays an important role when heating with wood.
An alternative to wood is wood briquettes, which have low moisture content and longer burning time, but are more costly. The briquettes must be placed in a hot bed, but their placement in the firebox does not affect the quality of combustion as much as wood.
Another option is pellets, which offer automated dosing and high efficiency, but their purchase price is higher.
Comparison of heating costs by fuel type.
Combustion efficiency is another important factor that affects fuel consumption and emissions. Modern stoves achieve an efficiency of over 78 %, which means that about four-fifths of the energy extracted from the fuel is converted into heat. This results in low operating costs and minimal environmental impact.
Stove material and construction
In addition to stove performance and fuel type, it is important to consider the material and construction of stoves and fireplace inserts.
Stoves made of stove steel transfer heat quickly, while cast iron stoves have a high heat storage capacity. Depending on their size and weight, they can continue to transfer heat to the room for a further 4 to 6 hours after the fire has gone out.
Tiles made of tile, soapstone or sandstone, used especially in stoves constructed of stove steel, can improve heat accumulation and contribute to the aesthetic appearance of the stove.
For specific requirements, hot water stoves that allow heat to be distributed to other rooms via a heat exchanger may also be suitable.
Dimensioning and design of the chimney
The chimney is a key element of the heating system and its correct dimensioning affects both safety and efficiency of operation. An incorrectly sized chimney can lead to flue gas problems, which negatively affects the efficiency of the stove and increases the risk of soot build-up.
In addition to the diameter, the draft of the chimney, its height and material must also be taken into account. The correct design of the chimney, including the possibility of combustion air intake, is essential to ensure the optimum functioning of the heater and the entire heating system. For these reasons, it is advisable to consult a chimney design expert.
The first thing to do is to choose the heater and then design the optimal chimney for it. In existing buildings it is necessary to assess the condition of the chimney according to the selected heater and decide whether it is sufficient for the selected stove or fireplace insert, whether it will have to be lined or completely demolished and replaced with a new one.
To commission a new indoor heater, you can't do without a flue inspection. This is a legal requirement whether you are building a brand new chimney, modifying an existing chimney or if you are connecting a new heater to the flue. A chimney sweep - a flue inspection engineer - will issue you with a flue inspection report including a flue calculation.
Conclusion
The right choice of indoor heater and chimney is essential for efficient and safe heating. A well-made selection and design ensure not only fuel savings and comfortable heating, but also the long-term durability of the entire system. Working with an expert is therefore always worthwhile.
