Future potential of clay products

Clay-based building products can make a significant contribution to the necessary transformation of the construction industry: the raw material is available in vast quantities, the manufacturing process is remarkably energy-efficient, and the material can be recycled indefinitely. The moisture-buffering capacity of the surfaces and the high thermal storage mass ensure a healthy indoor climate. New developments are emerging in drywall construction, load-bearing structures, and the use of clay products as enablers of circularity for other building materials.

Availability

As a virtually inexhaustible raw material, clay occurs naturally. No dedicated pits are required for its extraction: construction clay is often found as a top layer during gravel and sand mining. Large quantities of clay are also excavated and disposed of during construction projects. We simply need to utilize it; the raw material is available in almost unlimited supply. Clay can be sourced and used regionally, which saves fossil fuel energy for transport and reduces road traffic.

Like wood, clay is a raw material that can be used directly as a building material. Many clay products consist of only a few components, such as clay, sand, and natural additives like straw. Mixing is not a highly complex production process, and chemical additives are unnecessary. This simplicity ensures supply security even in difficult times, and ecological and social standards are easy to guarantee.

Energy consumption in building material production

The energy required for the production of building materials determines the majority of greenhouse gas emissions and, consequently, the climate footprint. Time is of the essence: according to the UN Environment Programme's "Global Status Report for Buildings and Construction," the construction and building sector accounts for 40% of global CO2 emissions. Clay building materials have major strengths here. Many clay products are even climate-positive due to the CO2-storing plant fiber content.

Clay mortar and many other clay building materials can be produced, stored, and processed entirely without drying. The natural moisture content of the raw material in the ground ("earth-moist") is simply retained. An electric motor, preferably powered by solar energy, homogenizes the raw material and mixes it with sand and straw. It doesn't get more energy-efficient than that.

This is different for mineral binders like cement, lime, or gypsum: the water bound within the structure of the parent rock, known as crystal water, is first burned off, and then the rock is ground into powder. To enable plastic processing on the construction site, water is added back in; on the wall, the material then hardens back into a type of stone through the chemical integration of this water. Clay does not have this energy-intensive loop; it hardens through simple drying.

Circularity

A decisive factor for the sustainability and future viability of building materials is their potential for recovery. Mineral building materials are generally crushed and used for lower-grade applications, such as road construction. This is called "recycling," but it should actually be referred to as "downcycling." In contrast, new clay products can be made from old clay products indefinitely. This is due to the nature of their bonding: clay building materials are water-bound, meaning they are also water-soluble. Even after decades or centuries, they can be reshaped without any loss of value. Almost any clay product can be made from any other clay product. This "cross-compatibility" is unique.

However, water solubility also means water sensitivity. In the past, this was seen as a disadvantage. This was based on the misunderstanding that the entire outer wall, including the weather-exposed layer, consists of clay; however, clay products are only sensible and in demand for interior work. There, water sensitivity is irrelevant. To clarify: plasterboard panels are also water-sensitive, yet they are very successful on the market. No one would even consider using them as facade panels. It is the same with clay products, where the alleged disadvantage is a central advantage from a sustainability perspective.

Indoor climate

A good indoor climate is created by balancing, breathable surfaces and thermal storage mass. Clay building products can absorb large amounts of humidity and release it again when the air is dry; pollutants and odors can be bound or even neutralized. Heavy clay products act as thermal storage, cooling the interior during high summer temperatures. This capability has gained significant importance in recent years. Unlike air conditioning systems, clay components work on a "low-tech" principle. Their functionality requires neither electronic control nor energy consumption or maintenance costs.

An important area of application for clay building products is wall heating and cooling systems. They are the order of the day: when heating, they work with low flow temperatures, meaning only moderately heated water. This significantly increases the energy efficiency of heat pumps and often makes them economically viable in the first place. The combination with clay further enhances this effect. The natural, vapor-permeable clay plaster surfaces are the perfect heat-emitting medium, both functionally and aesthetically.

Future markets for clay building products

The most important areas of application for clay building products in recent decades have been interior plastering, surface design, as well as timber frame renovation and interior insulation. Drywall applications, load-bearing clay masonry, and thin-bed clay mortar for bricks and other artificial stones point the way to the future.

Drywall construction

Drywall construction with clay boards has developed particularly strongly in recent years compared to other clay product techniques. The reasons: drywall partitions are quick and easy to install, and properties regarding sound and fire protection can be reliably specified. Public clients are also showing increasing interest; construction projects with a volume of several thousand square meters of clay board cladding are no longer a rarity. Here, the excellent environmental properties ("EPD") of many products are a primary argument for their use. Since the beginning of the year, a purely solar-dried clay board has even been on the market. The first manufacturers are publishing drywall compendiums with precise details on constructions and solutions. Clay boards are also catching up in terms of testing and approvals, although there is still a good way to go here.

Load-bearing clay masonry

Since the middle of last year, DIN 18940 has provided a modern design standard for load-bearing clay masonry. The standardization initiative was launched by the Dachverband Lehm e.V. in Weimar. For the first time, it is possible to build class 4 buildings with clay brick walls up to 13 m high. Since the regulations were based solely on experience with small-format masonry, economically bonded modern masonry made from large precision blocks is not yet included. Fortunately, there are currently several manufacturer initiatives working on approvals for these contemporary and cost-effective masonry variants.

Bonding bricks and hydraulically bound blocks with clay

The ability to create reversible connections also benefits other building materials, allowing them to realize their circular potential: bricks, sand-lime bricks, or lightweight concrete blocks bonded with clay mortar can be reused, whereas those bonded with cement mortar cannot. If energy-intensively produced and structurally high-performance masonry units are reused multiple times, their environmental performance improves significantly. It is important that interior coatings can also be detached and separated by type, which is the case when using clay plaster mortars. Approvals for this will also be available in the foreseeable future.

Clay building products – now!

The innovations described will sustainably change and significantly expand the use of clay building products. However, this should not distract from the fact that the applications introduced today have already taken very important steps toward a construction revolution. Clay products are now highly developed and readily available. None of these applications are still considered experimental; clay building products have been standardized in Germany since 2013, now in their third generation of standards. There are no real obstacles left. Clay building products are available in a wide selection and a broad range of prices and technical specifications – they just need to be used!

The natureplus podium for members

In our Podium section, natureplus members have their say. Solutions, innovations, success stories, knowledge, questions, calls to action, and much more: everything that brings us a step closer to the construction revolution can be shared here with the natureplus network. Would you also like to publish an article in the natureplus news? Please get in touch! Melinda Meisel - meisel@natureplus.org

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