Clay is comfortable

Clay is comfortable

Clay is old, but not outdated - this is demonstrated by the southern German company Naturbo based in Görisried in the Allgäu. The clay building panels developed and produced there are more than ecological niche products: they are part of an innovative, industrially manufactured clay plaster dry construction system that can be used for heating, cooling and insulating. According to Naturbo managing director Michael Weihele, the product is “so far unique on the market”. What sets it apart from other wall systems for cooling and heating: the combination of high industrial prefabrication, the versatility of clay plaster and the special structure of the panel.

Relics from the GDR

At the AHF primary and secondary school in Markkleeberg, Saxony, two architecturally very different buildings that were built during the GDR era are currently being renovated - a listed plastered building from the 1950s and a steel building from the Leipzig Lightweight Metal Construction Combine from the 1970s. Both buildings will be modernized according to ecological criteria. More than 2,300 square meters of wall and ceiling area will be equipped with Naturbo's clay plaster dry construction system.

“Our energy consultant made us aware of Naturbo,” says Daniela Schörner, board member of the Bildungs-Bau cooperative, which is responsible for the project. “After we met the managing director Michael Weihele personally on the construction site and he presented the product portfolio with great enthusiasm, it quickly became clear to us: This fits our concept.”

“We are always impressed by these products: an insulation board, plus heating, plus cooling and a circuit-protecting, climatically perfect clay finish – all in one,” continues Schörner. The school's concept for the renovation is based on three principles: preserving the existing building, reducing technology and using natural materials. Schörner: "We install as little technology as possible, which is why we don't have a ventilation system. Naturbo gives us the opportunity to cool the rooms without air conditioning using the wall heating system, which means we can achieve good cooling in the summer."

This is made possible by the specific properties of clay – and the special structure of the Naturbo panels. Managing director Michael Weihele: "With traditional wet processing, clay has the problem of long drying times and a high susceptibility to cracking. We have solved this in our production. Our panels are industrially prefabricated. The pipe is already integrated, the clay is dried. The panels just have to be connected on the construction site - done." A wall or ceiling heater with clay can be installed and used in a short time.

Clay has real advantages in terms of building physics. “Clay conducts heat and cold very well and can buffer moisture,” says Weihele. Moisture management is particularly important when cooling: If the surface temperature of a wall falls below the so-called dew point, which is usually around 17 degrees, condensation forms. Normal systems then switch off to avoid damage, or the use of a ventilation system is necessary. Clay, on the other hand, can absorb this moisture. “This means we can easily cool below the dew point for several days,” says Weihele.

Another advantage: by buffering air humidity, clay stabilizes the indoor climate not only in terms of temperature, but also air quality. "We know that, especially in schools, a stable indoor climate with medium humidity improves the concentration and well-being of the students. Clay contributes to exactly this - and all without any technology," emphasizes Weihele.

The plate structure is clever. The basis is a soft wood fiber board, which acts as insulation. A multi-layer aluminum composite pipe is inserted into this at the factory, which is then covered with a ten millimeter thick layer of clay plaster. The soft wood fiber acts as a thermal separation from the shell wall, while the clay acts as a heat conductor to the inside. “Heat looks for the easiest route – in our case directly into the room,” explains Weihele. "In this way we avoid heat loss to the rear. This is one of our most important unique selling points."

The heat is released via infrared heat radiation, which is perceived as particularly pleasant. "It's comfortable and cozy, like a tiled stove or the sun. You can feel the warmth within ten to fifteen minutes," explains Weihele. And: Due to the high proportion of radiation, the room temperature is perceived to be up to three degrees warmer than the air temperature actually is. This saves energy – according to the manufacturer, up to 18 percent.

For the school in Markkleeberg, this not only means a more ecological indoor climate, but also significantly lower operating costs. The combination of Naturbo heating-cooling panels, an air/water heat pump and a PV system on the roof forms a harmonious overall system. In addition, motorized windows and mechanically controlled doors enable effective cross ventilation at night.

With a view to use in construction, Weihele emphasizes the practical benefits of the solution: "Installation is quick, clean and easy. This makes our systems particularly attractive for renovations - whether in old buildings, monuments or new buildings." The supply chain also plays a role. "We manufacture everything here in the Allgäu. Quality assurance is high, transport routes remain short. And we are close to our customers."

Despite the current difficult situation in the construction industry, Naturbo says it is growing strongly. “We increase by around forty percent every year,” says Weihele. “And this despite the fact that the market as a whole has declined.” The growth is also necessary because the company has invested in automation and wants to keep the products affordable. "We have even reduced prices three times in the last few months - not because we are selling poorly, but because we are convinced that ecological building materials have to be cheap if they want to be widely accepted. Every builder should be able to afford healthy living."

With around 30 employees and an annual turnover of around four million euros, Naturbo currently produces exclusively in Görisried. Sales take place directly – both to craft businesses and to private builders. "Our products require explanation. Personal advice is crucial - and traditional retailers can hardly provide that."

Austria is a promising market for Naturbo. “As the crow flies it’s only 10 km from us to Tyrol,” says Weihele. "We see a lot of potential in Austria; our system can be combined excellently with timber construction. We are already working with a few craft businesses, but there could easily be more."

Naturbo also focuses on further development in the long term. “We want to further expand industrial production, but always remain true to our claim: to provide technically well-thought-out, healthy building materials for practical use,” says Weihele. Research and development take place directly in the company. It's not about speed, but about quality - and about convincing people about sustainable construction. Or as Weihele says: “In the end, it’s about creating more comfort with less energy – and we can do that really well with clay.”