Walltherm Vajolet: Experience Wood Gasification Excellence


I recently had the opportunity to explore the Walltherm Vajolet, a wood gasification stove that doubles as a water heater, designed for use in a living room setting. This innovative product from Wallnöfer is a remarkable blend of traditional stove aesthetics and the efficiency of a reverse combustion log gasification boiler.

Walltherm Vajolet

How Wood Gasification Stoves Work

Walltherm Vajolet

Wood gasification stoves, also known as wood gas stoves, utilize a two-stage burning process to burn wood more efficiently and cleanly than traditional wood stoves. In the first stage, called pyrolysis, wood is heated in a low-oxygen environment, preventing it from burning conventionally. Instead, this process breaks down the wood into volatile gases (such as hydrogen, carbon monoxide, and methane) and charcoal. These gases, commonly referred to as wood gas or syngas (synthesis gas), are then drawn into a separate combustion chamber. In this second stage, the wood gas mixes with a controlled amount of oxygen, allowing it to burn at a higher temperature than standard wood burning. This results in more efficient and cleaner combustion, significantly reducing smoke and pollutant emissions. The high combustion temperature ensures a more complete burn, thereby extracting more heat from the same amount of wood and producing minimal ash. Wood gasification stoves are thus considered a more environmentally friendly option, especially in areas where wood is a primary fuel source. They are part of the broader biomass gasification technology used for various energy generation applications.

Quick Specifications

  • Efficiency: 90.8%
  • Nominal Heat Output: 10 kW
  • Heat Output Range: 8 – 15 kW
  • Fine Particles: 13.2 mg/Nm³
  • Combustion Chamber Size: 55 liters
  • Weight: ~300 kg (without water)
  • Dimensions: Height – 1373 mm, Width – 531 mm, Depth – 635 mm
  • Warranty: 5 years on the body, 2 years on fittings and electrical components

The upper combustion chamber is made of stainless steel for longevity, and the stove is available in multiple colors, including black, grey, and white-silver combinations.

Design and Build Quality

Walltherm Vajolet

The Walltherm Vajolet, crafted by Wallnöfer, exemplifies a perfect blend of style and durability in its design and build quality. The use of stainless steel for the upper combustion chamber not only enhances its visual appeal but also promises longevity, ensuring that the stove withstands the test of time. Available in a range of colors including classic black, sophisticated grey, and chic combinations of white with black or silver, the Vajolet offers versatility to match various interior design preferences. This thoughtful approach in design ensures that the Vajolet is not just a functional piece of heating equipment, but also a stylish addition to any living space, making it a standout in both aesthetics and construction.

Performance and Efficiency

Walltherm Vajolet

The performance and efficiency of the Walltherm Vajolet are key factors that set it apart in the market of wood-burning stoves. Its design and technology contribute to a level of efficiency and environmental friendliness that is highly commendable.

  1. At a 90% efficiency rating, the Vajolet operates at a significantly higher level than many traditional wood stoves. This high efficiency means that more heat is extracted from the same amount of wood, ensuring a warmer home with less fuel.
  2. The core of the Vajolet’s performance lies in its wood gasification process. This process involves heating wood in a low-oxygen environment to produce wood gas, which is then combusted at high temperatures. This not only maximizes the energy extracted from the wood but also ensures a cleaner, more complete burn.
  1. The Vajolet’s design minimizes environmental impact, emitting only 13.2mg of dust. This low emission level is indicative of a clean burn, making the Vajolet an eco-friendly option for home heating.
  2. The stove’s gasification process is remarkably efficient, utilizing less wood than traditional stoves to produce the same or even more heat. This efficiency is not just beneficial for the environment by reducing deforestation pressures but also economical for users in terms of fuel savings.
  3. The Vajolet efficiently distributes the heat it generates. Most of the heat produced is used to warm the living space, while a portion can be used to heat water, making it a comprehensive heating solution.
  4. The efficiency of the Vajolet means that users can expect to spend less on wood over time. This is particularly beneficial in the long term, both from a financial and an environmental standpoint.

Heat Distribution

Walltherm Vajolet

The Walltherm Vajolet exhibits exceptional heat distribution capabilities, thoughtfully designed to maximize both efficiency and comfort in home heating. Approximately 80% of the heat generated by the Vajolet is allocated for central heating, showcasing its effectiveness as a primary heat source for homes. This feature is especially beneficial in larger spaces or colder climates where maintaining a consistent, comfortable temperature is essential. In addition to central heating, the Vajolet also provides 20% radiant warmth, delivering immediate and comfortable heat to the living area surrounding the stove.

This balance ensures that while the majority of the heat efficiently supports the central heating system, the ambiance and warmth of traditional stoves are still very much present. The Vajolet’s capacity to heat spaces up to 150m², coupled with its ability to supply domestic hot water, further underscores its versatility and utility. It’s not just a source of warmth but a comprehensive heating solution, efficiently utilizing energy for both air heating and water supply. The Walltherm Vajolet, therefore, stands out as an efficient, multifunctional heating system, ideal for a range of living environments and needs.

Pros and Cons

Pros of Walltherm Vajolet
  1. High Efficiency: With an efficiency rating of around 90%, the Vajolet is one of the most efficient wood gasification stoves on the market. This high efficiency means less fuel is used for more heat output.
  2. Eco-Friendly: The stove boasts low emissions, particularly in terms of dust particles (only 13.2mg), making it an environmentally conscious choice.
  3. Innovative Design: Combining wood gasification and reverse combustion, the Vajolet represents the cutting edge in stove technology. This design ensures a more complete burn and higher heat output.
  4. Effective Heat Distribution: It efficiently distributes heat (80% for central heating and 20% as radiant warmth), making it effective for both room heating and central heating systems.
  5. Large Heating Capacity: Capable of heating a space up to 150m², it’s suitable for larger homes or spaces.
  6. Aesthetically Pleasing: The double windows offer a view of the flames, adding a visual charm to its functional appeal.
  7. Robust Construction: Made with quality materials like stainless steel, the Vajolet is built for durability.
Cons of Walltherm Vajolet
  1. High Initial Cost: Advanced technology and materials mean the Vajolet comes at a higher initial cost compared to simpler wood stoves.
  2. Complex Installation and Operation: The advanced features of the Vajolet may require a more complex installation and learning curve for optimal operation.
  3. Size and Weight: Its substantial size and weight could be a limiting factor for some homes, both in terms of installation and space requirements.
  4. Fuel Specificity: The stove’s efficiency is highest when using specific types of wood, which might not be readily available or affordable for all users.
  5. Regular Maintenance: To maintain its high efficiency and low emissions, the Vajolet requires regular maintenance and cleaning.
  6. Dependence on Wood Supply: As a wood-based heating solution, its effectiveness is contingent on a steady supply of wood, which might be an issue in some regions.

Additional Features

The Walltherm Vajolet is further enhanced with additional features that cater to both convenience and efficiency. It is equipped with air-cooled handles, which significantly improve user comfort and safety. These handles are designed with customizable positioning, allowing users to adapt the stove to their specific installation and usage preferences. Additionally, the Vajolet boasts double-glass doors, a feature that not only elevates its aesthetic appeal but also contributes to its overall efficiency.

Walltherm Vajolet

These doors are designed to retain heat more effectively, ensuring maximum heat output and energy conservation. Available in options of stainless steel or a special edition black, the doors add a touch of elegance and sophistication to the stove, making it a stylish addition to any living space. These thoughtful features underscore the Walltherm Vajolet’s commitment to combining functional excellence with modern design.

Recommended Accessories

WAL04 accessory.

The Walltherm Vajolet’s functionality can be significantly enhanced with the addition of the WAL04 accessory. This accessory serves as a digital solar thermal controller, designed to optimize and monitor the stove’s operation. It provides real-time data display of critical parameters such as exhaust gas temperature and water temperature within the stove. This information is crucial for maintaining efficient and safe operation, allowing users to adjust settings for optimal performance.

Additionally, the WAL04 includes an integrated alarm system. This safety feature is particularly important, as it alerts users if the exhaust gas temperature rises beyond a certain threshold, ensuring that any potential issues are addressed promptly. The incorporation of the WAL04 accessory into the Walltherm Vajolet system demonstrates a commitment to not only enhancing user experience but also prioritizing safety and efficiency in home heating solutions.

Benefits of Wood Gasification Stoves

Wood gasification stoves offer a range of benefits, making them a popular choice for those seeking efficient and environmentally friendly heating solutions. Here are some of the key advantages:

  1. Wood gasification stoves are significantly more efficient than traditional wood stoves. They achieve this by burning both the wood and the gases released from the wood, which means more heat is extracted from the same amount of fuel.
  2. These stoves emit fewer pollutants compared to conventional wood stoves. The high-temperature combustion in the gasification process ensures a more complete burn, which significantly reduces the emission of smoke, particulate matter, and other harmful pollutants.
  3. Due to their higher efficiency, wood gasification stoves use less fuel to produce the same amount of heat, leading to cost savings in terms of fuel consumption over time.
  4. Wood is a renewable resource, and when sourced responsibly, it can be a sustainable fuel option. Wood gasification stoves make better use of this resource, aligning with environmentally conscious heating practices.
  5. These stoves are capable of producing a steady and consistent heat output. This is due to the controlled gasification process, which maintains a constant temperature and burn rate.
  6. Modern wood gasification stoves are designed with safety in mind. They often include features like sealed combustion chambers and automatic shut-off systems, reducing the risk of accidents.
  7. While they are optimized for wood, many gasification stoves can also efficiently burn other types of biomass fuels, providing flexibility in fuel choice.
  8. Advanced models like boiler stoves can integrate into a home’s central heating system, providing not just space heating but also domestic hot water.
  9. Many wood gasification stoves are designed with an eye for aesthetics, often featuring viewing windows that allow you to enjoy the sight of the flames.
  10. By burning wood more completely and efficiently, these stoves help in reducing the overall carbon footprint associated with home heating.

Is This Worth to Buy?

The Walltherm Vajolet, with its 90% efficiency rating and eco-friendly low emissions, presents a compelling option for those seeking an advanced, sustainable heating solution. Its ability to effectively distribute heat for both central heating and radiant warmth, coupled with its aesthetic appeal and functionality in heating large spaces and providing domestic hot water, makes it an attractive choice. However, the decision to purchase should consider the higher initial cost, installation and maintenance requirements, availability of suitable wood fuel, and local wood-burning regulations. If these factors align with your budget, environmental goals, and lifestyle preferences, then the Walltherm Vajolet could indeed be a worthy investment, offering a blend of efficiency, eco-consciousness, and modern design.


The Walltherm Vajolet stands as a testament to innovation in home heating solutions, marking a significant leap forward in this technology. By seamlessly blending high efficiency, environmental friendliness, and aesthetic appeal, it emerges as an ideal choice for modern homeowners who prioritize sustainability without compromising on power and style. The Vajolet’s unique features, from its high-temperature combustion and efficient heat distribution to the additional comforts of air-cooled handles and elegant double-glass doors, set it apart in the market. The integration of accessories like the WAL04 further underscores its commitment to safety and operational efficiency.

As we conclude this review, we encourage you, our readers, to share your thoughts and experiences. Have you used the Walltherm Vajolet or similar wood gasification stoves? What aspects of home heating are most important to you? Your insights and discussions enrich our understanding and help others make informed decisions. So, please, comment below, share your experiences, and let’s continue the conversation about advancing home heating solutions for a sustainable future.


  1. What Type of Chimney is Required for the Walltherm Vajolet?
    The Walltherm relies on natural draft, so a chimney with at least 12Pa, preferably 15Pa draft, is essential. A chimney with a vertical length of 6m or more and a diameter of 150-200mm, insulated and ideally connected at a 45° or 60° angle (instead of 90°), works best.
  2. Will There Be Condensation in the Chimney?
    No, the Walltherm prevents condensation by initially heating up with high-temperature fumes over 300°C, drying out any humidity. This preheating phase ensures that even when the exhaust temperature drops to 130-170°C during gasification, chimney sooting won’t occur.
  3. Which Type of Wood Should be Used?
    Wood should be dry, stored for at least 2 years, and have less than 20% humidity (15% is ideal). Both soft and hard woods are suitable. The combustion chamber accommodates logs up to 35cm long and has a ~50-litre capacity. Burning time varies from 3-4 hours with soft wood to around 5 hours with hard wood.
  4. Does Smoke Escape When Adding More Wood?
    If the chimney draft is adequate, smoke should not escape. Opening the exhaust fume flap before adding wood allows smoke to exit through the chimney, minimizing escape into the room.
  5. What is the Cleaning Procedure for the Stove?
    Daily removal of ashes from both combustion chambers is recommended. Weekly, clean the ash boxes below the cast iron grids using an ash vacuum cleaner. The heat exchanger should be cleaned every 6-8 months with the provided steel brushes.
  6. What are the Wear Parts and Their Lifespan?
    Door and cleaning opening sealings should be replaced every 2-3 years. The stainless steel injector block and cast iron grids last about 2-5 years. Refractory stones, despite surface cracks, need replacement only after 5-8 years. The lower combustion door glass may require replacement due to high-temperature exposure.
  7. Recommended Size for the Storage Tank?
    Regulations vary, but generally, a tank of 1000 liters or more is recommended. In Germany, for example, the law requires 55 liters per 1 kW of output, equating to a minimum of 600 liters for the Walltherm.
  8. Are There Special Requirements for the Heating System?
    The Walltherm delivers energy to a storage tank, which then feeds the heating system. The heating system’s pumps (for floor heating or radiators) must not run if the water in the storage tank is cold. Heating controllers should check the storage tank temperature before activating pumps.
  9. Why is the Stove Connected Through a Pump Unit with a 3-Way Valve?
    The pump unit with a 3-way valve maintains the water temperature in the stove’s heat exchanger above 60°C, preventing condensation and ensuring efficient burning. The 5-year warranty is valid only if the stove is used with a properly working pump group with a 3-way valve.
  10. What are the Installation Requirements for the Stove?
    • A chimney with sufficient natural draft.
    • A floor/ceiling capable of supporting 300kg or more.
    • Connections for two pipes (flow and return), fresh water, and a drain.
    • If combustion air is external, an air channel leading to the stove’s position.
    • Adequate distance from flammable objects, typically 20cm, and placement on a non-inflammable surface.
David Murray
David Murray
Forestry Author

I'm David Murry, a forestry equipment specialist with a focus on chainsaw operation. With over 13 years of experience, I've honed my skills in operating and maintaining a wide range of machinery, from chainsaws to log splitters. My passion for the outdoors and commitment to sustainable forestry drive my work, which emphasizes safety, efficiency, and staying updated with industry advancements. Additionally, I'm dedicated to sharing my expertise and promoting environmental awareness within the forestry community.


It looks very interesting as a whole home heating solution (with appropriate backup source). However, doesn't look like any North American dealers. Are you aware of a similar model of hydronic wood stove in US?

Daniel Adams
January 3, 2024 9:08 pm

The Walltherm Vajolet does look like a great option for a whole home heating solution, and I agree that it's a shame there aren't any North American dealers that I'm aware of. However, there are a few similar hydronic wood stove models available in the US that you might want to consider. Ekoheat boiler stove. It's made in Canada and has a similar output to the Vajolet, at around 12 kW. It also has a high efficiency rating of 86%, and it can be connected to a thermal storage tank for increased efficiency. However, it's not quite as compact as the Vajolet, so you'll need to make sure you have the space for it.

Kristin Watsons
David Murray
January 8, 2024 12:29 am

How does one get one of these into the US?

Daniel Adams
December 13, 2023 4:02 am

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