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Open-chamber wall-mounted boilers

Wall-hung open-flue boilers for outdoor installations or well-ventilated rooms: they draw air from the room and are often the most economical choice for heating and hot water. Brands like Ferroli, Ariston and Beretta ready to ship, from 370 to 1308 euros.
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What are open-flue wall-hung boilers?

The open-flue wall-hung boilers, also known as natural-draught boilers, draw the air needed for combustion directly from the room where they are installed and expel the flue gases through the natural draught of the chimney. They are simple and reliable appliances, generally more economical than sealed-chamber models, and they remain a valid solution when the installation conditions allow it. In our catalogue you'll find 38 models, all available, with outputs suited both to heating alone and to the production of domestic hot water.

Difference between open flue and sealed chamber

The difference concerns the way the boiler handles air and flue gases. In the open flue, the combustion air is taken from the room and the flue gases leave by natural draught, so a well-ventilated room is needed. In the sealed chamber, on the other hand, the combustion circuit is isolated from the room: the air comes from outside and the flue gases are expelled by a fan, making the appliance installable even in enclosed spaces. If you're looking for a more modern and efficient model, consider the condensing boilers or the entire range of wall-hung boilers.

When open-flue boilers are permitted

For safety reasons, natural-draught boilers can only be installed under certain conditions: outside the home, on balconies or terraces, or in technical rooms and sufficiently ventilated spaces, with the air vents required by regulation. They are not permitted in bathrooms, bedrooms and rooms lacking adequate ventilation. Before buying, it is worth checking with a qualified installer that the space meets the requirements, so you can choose the right model in full safety.

Output and sizing in kW

The output is chosen based on the area to be heated and the hot water needs. As a general reference, you can orient yourself as follows:

  • 24 kW: medium-sized apartments, with heating and hot water for one bathroom.
  • 26 and 28 kW: larger homes or those with greater domestic hot water demand.
  • 32 kW and above: large homes or installations with two simultaneous draw-off points.

Excessive oversizing brings no advantage and increases consumption, so it is best to leave the sizing to a technician.

Domestic hot water production

Most of these models are of the combi type, meaning they provide both heating and the production of domestic hot water with an instantaneous heat exchanger. This means hot water at the moment the tap is opened, without the need for a storage tank. If instead your hot water demand is high or independent of the heating, it may make sense to also consider a dedicated water heater or a heat-pump water heater.

The best brands available

You'll find the leading manufacturers in the sector, with official warranty and available spare parts: Ferroli, Ariston, Beretta, Riello, Baxi, Chaffoteaux and Fondital. Prices start at around 370 euros and reach the most complete solutions, for every budget.

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Frequently asked questions

What is the difference between an open-flue and a sealed-chamber boiler?
The open-flue boiler takes the combustion air from the room and expels the flue gases by natural draught, so it requires a well-ventilated room or outdoor installation. The sealed chamber has an isolated combustion circuit, takes air from outside and discharges the flue gases with a fan, so it can be installed even in enclosed spaces.
Where can I install a natural-draught boiler?
Only outside the home, on balconies and terraces, or in technical rooms and sufficiently ventilated spaces with the air vents required by regulation. They are not permitted in bathrooms, bedrooms and rooms lacking adequate ventilation.
Are open-flue boilers still compliant?
Yes, they remain saleable and installable when they meet the required safety and ventilation conditions. Checking the compliance of the room is always up to a qualified installer before mounting.
How many kW do I need for my apartment?
For a medium-sized apartment with one bathroom, 24 kW is generally enough. For larger homes or those with greater hot water demand it is worth going up to 26, 28 or above 32 kW, leaving the precise calculation to a technician.
Do these boilers also produce domestic hot water?
Most models are combi and produce domestic hot water instantaneously, so at the moment the tap is opened and without a storage tank. There are also versions dedicated to heating alone.
Is an open flue or a condensing boiler the better choice?
The open flue has a lower initial cost and is suited to outdoor installations or ventilated rooms. The condensing boiler consumes less and more easily qualifies for tax incentives where applicable, such as reduced VAT for renovation work, so it is preferable when long-term efficiency is the priority.
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