By improving a building’s energy performance, wood-burning fires can now provide much of the heat that the building needs and significantly reduce your energy bill. Special attention must be paid to the size of the fire to make sure your product works for you and functions as efficiently as possible.
Above all, make sure that your fire’s heating power suits the space it will heat and the insulation in place. With this in mind, start by calculating the amount of heat you need, expressed in kilowatts (kW). The power you need will depend on what you want to use your fire for: as the main source of heat, or for occasional heat.
As an example, for a next-generation occasional burner, we recommend 1kW to heat 10m² with average insulation, and 15m² in a low-energy home. The output of next-generation burners is actually 80%, compared to 20% for an open hearth or fire. Whereas before, 80% of the energy in the wood was lost into the sky, with a Stûv, 80% of the energy now stays inside your home. Savings guaranteed!
Next-generation fitted stoves and fires have a wide range of uses: with a given quantity of wood, you can reduce the heat released by reducing the air that goes into the fire. To get the most out of your fire, you will have to use it at its highest setting, in other words, at a high temperature, with logs covering the whole width of the base of the burner. Having a small fire in a large burner inevitably blackens the glass and produces pollution. Any kind of combustion releases different kinds of gas, such as CO, CO2 and fine particles, which can damage airways if they are present in excessive quantities. Thankfully, complete combustion helps to minimise these emissions. This means it is better for your health and for the environment.
The right heating power therefore needs to be at the high end of your burner’s usage range. This is when it becomes more economical and more ecological: it produces more heat and less waste. So it is important to choose the right size of fire.
Position of the smoke outlet
When you are choosing where to put your fire, you need to think about the smoke outlet. The ideal pipe is vertical, high enough, thermally insulated and topped off with a cover: it should be round with the right diameter, and the inside should be smooth. The pipe is preferably integrated in the building so it isn’t cooled down by the outside air: an outdoor smoke outlet pipe should always be insulated. Lastly, the chimney needs to be swept once a year.
Distribution of heat and view of the fire
The position of your fire will have a significant impact on what you see of the fire, the radius of heat that you will feel, and how the heat is distributed. A stove will distribute the heated air locally, while a built-in fire may distribute the heated air via pipes to rooms that are a long way away.
Crowding your home
Stoves are generally more compact. Suspended versions are also available to free up floor space. Built in burners and fires generally need a larger wall or mantel. Talk to your Stûv dealer to find out the space you need for the distribution of heat and the total size of the installation.
What is a wood-burning stove ?
A wood-burning stove is an independent heating system which is relatively straightforward to install. It produces heat by radiation and by convection. Some stoves can be fitted with a heat storage system, which distributes warmth around the building gradually.
What is a wood-burning insert ?
A wood-burning insert is a compact solution that can be built into an existing chimney or a hearth. It means you can convert an old chimney into an efficient, safe fireplace with a relatively small amount of work. They are also known as inset stoves.
What is a built-in fire ?
Built-in fires require more extensive work to install. However, they offer a wide range of options in terms of integration and customisation.
The inside walls are covered in heat-resistant material (stone, cast iron, vermiculite panels etc.), whose capacity for accumulation and radiation may vary.
The outside walls of the combustion chamber are covered in a double layer of metal which collects the energy produced and maximises output.
Obviously you need air for wood to burn, an average of 8m³ per 1kg of logs.
This air can be collected in 2 different ways:
Either straight from the outside, via a direct air inlet system. For enclosed and sealed fires, there is no interference with the air inside the building. This air intake can come through a wall or through the floor, so you will need to think about it right at the start of the project!
Or by taking it from inside the building. In this case, you will need to make sure that there is enough air for the needs of the building’s occupants and the fire.
Remember that an extractor hood that takes air outside the building and a ventilation system may hinder the performance of the fire.
Products fitted with a heat accumulator accumulate some of the energy from the wood and redistribute it gradually via radiation for the 8 to 12 hours after the fire has gone out. This helps maintain a pleasant temperature in the room you want to heat.
Products fitted with a heat accumulator also help to extend the time it takes for the temperature of the fire to rise. Thanks to the presence of enough material that can absorb a certain amount of energy as it heats up, the distribution of the heat produced by the combustion can be delayed. This delay can be useful as it means you can spread out the distribution of heat produced by the combustion and reduce the instant power of the fire during the accumulation phase. This heat accumulation system is particularly useful for buildings with low thermal inertia.
The presence of an ash pan is definitely practical, but it might lower the combustion temperature.
Most Stûv fires do not have an ash pan for this reason. The combustion is such that it does not produce much ash. As well as this, the space between the bottom of the fireplace and the edge of the fire is big enough to hold a bed of ash that should be left where it is. This bed of ash insulates the logs from the bottom of the fireplace, which is colder.
Do you dream of having an open fire? The crackling flames and the delicious smell of burning wood bring back childhood memories... which means that there are lots of Stûv fires that are perfect for you. Indeed, in their research, Stûv always tries to reconcile technical expertise and pleasure. Many wood-burning stoves and fires can work with an open flame or behind closed doors. In open fire mode, you can also add a barbecue kit, so you can enjoy some lovely wood-fired grills all the year round.
