Clay Foam FAQ – Insulation Questions Answered

There is no single “best” insulation material—the key factors are your home’s construction, condition, and requirements. For existing buildings with double-shell masonry, expanded clay foam is a particularly efficient and safe solution because it was developed specifically for this application. Expanded clay is blown into the existing air gap as a mineral insulation material, completely filling it and providing excellent thermal insulation (λ ≈ 0.034 W/mK), high fire resistance (fire resistance class A2, non-combustible), and reliable moisture protection while maintaining a vapor-permeable construction.

Core insulation using mineral insulation materials is particularly well-suited for the retrofitting of buildings with double-shell masonry. This method utilizes the existing air layer between the wall shells and fills it retroactively, an efficient solution requiring minimal structural work.
Mineral blow-in insulation materials, such as clay foam, which was developed specifically for the energy-efficient renovation of double-shell masonry and enables fast, clean, and sustainable insulation in existing buildings, have proven particularly effective:
•    completely and seamlessly fills the cavity
•    provides excellent thermal insulation performance (λ ≈ 0.034 W/mK)
•    is non-combustible and contributes to fire protection
•    is water-repellent yet vapor-permeable
•    remains permanently stable with no risk of settling

An insulation concept for double-leaf masonry is based primarily on efficient core insulation of the air cavity. First, the building is inspected for wall construction, moisture conditions, and accessibility. The insulation material is then installed in the existing air cavity.
Clay foam offers a solution that is easy to retrofit, completely and securely fills the cavities, meets high building physics requirements, and provides long-term, stable insulation performance.

Classic blow-in insulation works with loose flakes (e.g. mineral wool or cellulose) that are blown into the cavity layer. Clay foam, on the other hand, is foamed directly on the construction site in a machine, adapts to any unevenness and fills the air layer without gaps - even around wall ties and mortar pockets. In addition, it offers excellent settlement protection, moisture protection (hydrophobic and vapour permeable) and is non-combustible.

Clay foam was developed and extensively patented by BASF after years of intensive research with over 5,000 test formulations. Since its market launch in 2018, over 2000 houses have already been insulated with clay foam. BASF is the manufacturer of the clay foam components and supports the sales partners with expertise and experience. You can find more information at cavipor.com

Classic blow-in insulation works with loose flakes (e.g. mineral wool or cellulose) that are blown into the cavity layer. Clay foam, on the other hand, is foamed directly on the construction site in a machine, adapts to any unevenness and fills the air layer without gaps - even around wall ties and mortar pockets. In addition, it offers excellent settlement protection, moisture protection (hydrophobic and vapour permeable) and is non-combustible.

Clay foam consists of 90% inorganic components and 10% organic binder and is non-flammable due to its high mineral content. Furthermore, the product does not emit any harmful substances – neither during drying nor when subsequently remaining in the cavity layer. As the system is water-based and foamed with air, it also contains no organic solvents or blowing agents.

Clay foam has a lambda value λ_N= 0.034 W/mK and belongs to thermal conductivity group 035 - comparable to mineral wool and EPS.

Clay foam adheres and remains permanently in the masonry. It permanently retains its insulating effect both thermally and acoustically.

Although clay foam is hydrophobic, it is open to diffusion. Moisture exchange is still possible, so the wall remains breathable.

Clay foam is mineral and is categorized as construction waste according to LAGA (AVV 17 01 07). It can be disposed of with the rest of the construction waste or recycled, e.g. as a substructure material, without the need for complex separation.

Insulation with clay foam is eligible for subsidies. Clay foam is approved by the building authorities in Europe (ETA-19/0240) and fulfils high requirements for fire protection, sustainability and energy efficiency. Clay foam is EMICODE EC1 PLUS certified and fulfils environmental standards such as ISO 14025 and EN 15804.

You can find certifications, approvals, safety data sheets and more directly on the websites of the various clay foam sales partners.

The price depends on the building, the wall structure, the thickness of the air layer and the accessibility. For a quote, please contact a clay foam distributor.

The best way to insulate a roof depends on its use and construction. For example, over the top floor slab, between the rafters, or as above-rafter insulation. It is important to ensure gap-free insulation, moisture resistance, and fire protection.

Mineral insulation materials such as clay foam meet these requirements particularly well, as they are non-combustible, water-repellent, vapor-permeable, and low-emission, and are suitable for various roof and cavity constructions.

For between-rafter insulation, it is crucial that the insulation material be gap-free, dimensionally stable, and moisture-regulating. Since it is installed directly within the roof structure, fire safety and compatibility with wood are also important factors.
A suitable insulation material should:
·    completely fill the space between the rafters
·    remain dimensionally stable over time (no sagging)
·    exert no pressure on the wooden structure
·    regulate moisture and be vapor-permeable
·    be non-combustible or flame-retardant
Mineral-based, non-expanding insulation materials that are resistant to moisture and pose no risk of settling are particularly well-suited for between-rafter insulation. Clay foam meets these requirements exceptionally well and is therefore also suitable for use in roof structures and wooden buildings.

Clay foam is particularly well-suited for insulating floor slabs when cavities are present, such as in wooden beam ceilings: As a mineral-based in-situ foam, it is injected through small openings without producing dust or fibers, flows into all the gaps, and thus ensures seamless insulation with a very good thermal resistance value (WLG 035). At the same time, it is noncombustible, water-repellent, and vapor-permeable, which helps maintain a comfortable and consistently safe indoor climate.

Clay foam is particularly well-suited for historic buildings, as it is applied as a mineral-based on-site foam through small openings and preserves the existing building structure, a decisive advantage for architecture worthy of preservation. Thanks to its flowability, it completely fills cavities without requiring major interventions or changes to the building’s structure, while combining a good insulation value (WLG 035) with properties such as vapor permeability, non-combustibility, and high environmental compatibility, all of which are important for sustainable and heritage-appropriate renovation.

As an innovative class of materials, clay foam opens up new possibilities for sustainability-conscious developers — throughout the entire life cycle of the insulation material. Even the production process requires minimal resources and energy, resulting in a low carbon footprint. As a very low-emission building material, clay foam has been awarded the EMICODE^® EC1^PLUS seal and meets the highest environmental and health standards. In addition, clay foam is listed in the database of the German Sustainable Building Council (DGNB), allowing planners to directly access product-specific sustainability and life cycle assessment data (such as Environmental Product Declarations/EPDs) for their building certification.

Clay foam can be partially reused during renovation or demolition—for example, by returning processed material to the production process. In this way, the insulation material contributes both to resource conservation and to sustainable building renovation.

For environmentally conscious builders and developers, the primary consideration is insulation materials that are durable, energy-efficient, and resource-conserving. One interesting option is clay foam, a mineral-based insulation material made from clay. It improves the energy efficiency of buildings, is non-combustible, recyclable, and can be partially reintroduced into the production cycle. Thanks to its long service life and its contribution to reducing energy consumption, clay foam supports sustainable renovation and construction projects.

Anyone who values sustainability and high insulation performance should consider mineral-based blow-in insulation materials such as clay foam. Clay foam improves the energy efficiency of buildings and can thus reduce energy consumption for heating and cooling in the long term. At the same time, the material is durable, non-combustible, and recyclable. Thanks to its combination of good thermal insulation (WLG 35), long service life, and resource conservation, clay foam is an attractive solution for sustainable renovation and construction projects.

A special machine that is capable of conveying, foaming and mixing the three components in the correct ratio is required for the production and application of clay foam. You can obtain all further information on this directly from our technology partners.

Through the physical process of whipping the first component with air, a soap foam is created, which is then mixed with the other two components. This occurs continuously and automatically at the push of a button in the machine’s mixing chamber, immediately before the foam is applied to the wall.

Clay foam is a particularly user-friendly insulation material when it comes to quick and safe installation: Using a special machine, it is foamed directly on the construction site with air to ten times its original volume, without producing dust or fibers, and injected into the cavity through small drill holes. This makes it ideal for maintaining a clean construction site and a pleasant working environment, while at the same time ensuring fast and efficient insulation thanks to its easy application into cavities.

Please contact a clay foam technology partner for more information.

Clay foam is only installed by specialised companies and specially trained personnel. For more information, please contact a clay foam sales partner in your area.