What if we placed the stove not directly next to the chimney, but in the middle of the room? We would lay a longer flue pipe from the stove to the chimney, which would supply additional heat along the way.
Sounds logical, right? After all, the chimney is usually very hot. Why not use that heat?
And you know what? It actually works. But it’s not always a good idea.
A hot fireplace really heats things up.
When the stove is burning, hot exhaust gases flow through the chimney. These heat its walls, and the chimney then releases the heat into the room.
Some of the heat that would otherwise be directed up the chimney remains inside.
However, this does not mean that every additional meter of exhaust pipe automatically provides additional usable heating power.
So why not make the smoke vent extra long?
Because the chimney needs sufficiently warm flue gas to function properly.
Problems can occur if the exhaust gases become too cold in a long, uninsulated exhaust pipe:
- Weaker chimney draft – The oven may burn more slowly or be difficult to light.
- Flue gas condensation – Excessive cooling can lead to unwanted condensation.
- Exhaust gas path blockage Condensation, together with unsuitable combustion conditions, promotes the formation of deposits, including tar.
- Increased risk of a chimney fire – if flammable deposits form.
Simply put: If too much heat is extracted from the chimney flue, the remaining amount of heat may no longer be sufficient for it to function properly.
A stove in the middle of the room? That’s possible!
It is not forbidden in itself to place the oven further away from the chimney.
However, the length and course of the flue pipe cannot be chosen solely based on how much heat we want to gain.
Of particular importance are the length of the flue pipe, its gradient, the number of bends, the temperature of the flue gases, the required draft of the stove and the parameters of the chimney itself.
A long horizontal route can cause significantly more problems than a properly planned shorter connection.
Pay attention to safety as well! The surface of an uninsulated exhaust pipe can become very hot. It is necessary to maintain the prescribed distances to combustible materials, to securely seal penetrations in buildings, and to ensure the possibility of inspection and cleaning.
What about special heat exchangers for the exhaust duct?
There are also devices that additionally recover heat from flue gases.
However, this does not mean that they can be mounted on any stove.
Each of these elements alters the conditions in the exhaust gas path. It can influence the exhaust gas temperature, pressure losses, and chimney draft.
Therefore, it must be checked whether the manufacturer permits its use and whether the entire exhaust system is suitable for it.
Is it therefore worthwhile to use the waste heat from the fireplace?
Yes, provided that the exhaust system is correctly constructed and its heat transfer does not endanger the safe operation of the oven and chimney.
However, it is not advisable to extend the flue solely to extract the maximum amount of heat.
The length and construction must be assessed by a specialist based on the specific device and chimney.
Our final piece of advice
A chimney can provide additional heat. However, its main function is to safely vent exhaust gases, not to replace a radiator.
If you plan to place the oven in the middle of the room and use a longer flue pipe as an additional heat source, you should have such a solution checked by a professional beforehand.
Because a few degrees more heat are definitely not worth a poorly functioning chimney.