How clay creates cozy homes

For many people, the charm of a period home is hard to resist. But older buildings often lose heat unnecessarily, driving up both energy use and costs. That is where Cavipor^® comes in: a mineral clay foam developed by BASF that can insulate cavities in walls, roofs and ceilings. In this interview, Dr. Frank Reuter, Business Manager for Cavipor at BASF, explains what lies behind the innovation – and why it is ideal for the renovation of existing buildings. Here you can listen to the podcast with Frank Reuter.

Portrait of Dr. Frank Reuter, business manager Cavipor® at BASF.

Dr. Frank Reuter is business manager Cavipor^® at BASF.

What makes Cavipor special?

Dr. Frank Reuter: Cavipor is a mineral clay foam designed to insulate buildings. It is a real innovation in the insulation market. We initially developed it for cavity wall insulation in existing buildings with double-wall masonry, where two layers of brickwork are separated by an air gap. Because the foam flows so well, it can fill that space completely and without gaps. Cavipor has since been approved for other parts of the home too, including floor slabs and roofs. In other words, it can help insulate the entire building envelope.

What benefits does this bring for homeowners and residents?

It can help cut both energy use and costs, because less heat escapes through the building envelope. It also makes homes more comfortable to live in, keeping them warm in winter and pleasantly cool in summer. It also serves as a sound absorber and ensures pleasant room acoustics. Another advantage is that insulation can be added later with relatively little effort. Cavipor is easy to transport and can be applied cleanly by our trained specialist partners – without dust or fibers.

Stairs and ceiling with sound absorbing elements in the innovation building "NEST" in Zurich, Switzerland.

Cavipor serves as a sound absorber in the NEST innovation building in Zurich, Switzerland.

The consistency of Cavipor reminds of chocolate mousse.

How is Cavipor applied?

The foam system consists of three water-based components. On site, these are mixed with air to create the foam and then injected through small drill holes into the cavity inside the wall. Because the material flows so easily, it spreads evenly before it begins to gel. At that stage, it has the consistency of chocolate mousse and stays exactly where it is needed while it dries.

What are the advantages of clay foam?

The material is non-combustible, water-repellent and at the same time vapour-permeable. In other words, it protects the building without sealing it off. Cavipor also meets high emission standards. And we have thought about what happens at the end of its life, too: during future construction work, the material can either be recycled in line with local regulations or disposed of together with the resulting construction rubble.

BASF employees inspecting Cavipor in the lab.

Frank Reuter (left in the picture) developed Cavipor with his team at BASF in Ludwigshafen.

New Cavipor® use cases in the innovation building “NEST” in Zürich

Cavipor was used for the NEST innovation building of Empa (Swiss Federal Laboratories for Materials Testing and Research) in Zurich, Switzerland.

Is Cavipor already being used?

Together with distribution partners in Germany, the Netherlands, Ireland and the United Kingdom, we have already used the clay foam to insulate around 2,000 homes. Interest across Europe continues to grow: in Italy, for example, we recently insulated the first buildings. We can clearly see a demand for simple, sustainable solutions for energy-efficient refurbishment.

Why could Cavipor become even more important in the coming years?

A large share of Europe’s building stock was built before the turn of the century and now needs to be upgraded to improve energy efficiency. That calls for high-performance materials that are easy to apply, effective in use and safe to dispose of at the end of their life cycle. If we can make refurbishment simpler and safer, that benefits the climate, reduces energy consumption and improves quality of life. That is exactly what we hope to contribute to with Cavipor.

You can see the hands of laboratory staff inspecting the Cavipor clay foam.

Economical

Core insulation with clay foam leads to massive savings in energy costs.

Water repellent

Clay foam is hydrophobic and does not absorb liquid water.
wlp = 0.36 kg/m² water absorption (DIN EN 12087)

Non-expanding

The foam does not expand further and does not create additional pressure.

Sound-absorbing

Ambient noise is noticeably reduced by the use of this open-cell foam insulation.
Rw = 14 dB sound insulation index (DIN EN ISO 10140-2)

Cleanly processable

The water-based clay foam components can be easily transported and processed cleanly – without any dust or fibres.

Space-saving

The physical foaming with air creates a foam that exceeds the original volume by a factor of ten.

Gap-filling

Clay foam has excellent flow properties and perfectly adapts to the contours within the cavity. The foam fully surrounds installations and tight areas, including mortar protrusions and anchors.

Clay foam is self-sealing: it seals small slits or cracks in the masonry, prevents draughts and makes time-consuming preparatory and follow-up work unnecessary.

Fast

A single-family home can usually be insulated with clay foam within a day.

Safe

Clay foam consists of safe raw materials and is classified as a 'very low-emission building material' EC1 PLUS according to GEV-EMICODE^®standards.

Vapor permeable

The Clay foam is open to vapour diffusion. It is capable of absorbing and releasing moisture, thereby helping to regulate the indoor climate.
Vapor permeability μ = 3

Gentle facades

The fresh foam is injected into the cavity through small drilling holes.

Non-combustible

With a content of 90% inorganic components, dried clay foam is non-combustible - without the use of additional flame retardants.
Material classification A2- s1,d0 (DIN EN 13501-1)

Durable

Clay foam adheres well to mineral surfaces.

Recyclable

During dismantling, clay foam can easily be deposited with construction waste or reused as substructure material.

Insulating

The clay foam has an outstanding insulation performance of λN = 0.034 W/m•K (DIN EN 12667)

Dr. Frank Reuter is business manager Cavipor^® at BASF since 2022. In this role, he contributed to the development of Cavipor: An innovative mineral-based in-situ foam system for sustainable insulation. It aims at the energy-efficient renovation of double-wall masonry and opens new possibilities for the construction industry.

Reuter started at BASF in 2011 as a lab team leader. He has a PhD in Chemistry from University Mainz, Germany, complemented by an international study experience at the University of Bourgogne in Dijon, France.