Shells serve as floor insulation within pilot case ’t Centrum (Westerlo, Belgium)

14 February 2022 - Published by Eric Boessenkool
The construction team of ’t Centrum chose shells as a means of floor insulation. Teun Depreeuw, manager of Ecoshelp, explains.

What is shell insulation?

Teun: “Shell insulation merely consists of washed and sieved seashells. They can be reused endlessly because it is so compact and because the product has not been treated in any way. They are circular by nature.”

In which applications can you use seashells?

Teun: “Shell insulation is appropriate for many varied applications. From food supplements to animal feed stock and construction material.

We use shells to insulate with biobased materials. They are circular and multifunctional.

In construction they can, among other things be used for:

  1. Insulation of crawl spaces in existing buildings in which they will both insulate and form an air tight barrier that prevents moisture to rise.
  2. As an actual foundation for lighter (wooden) constructions due to its compact and insulating qualities.
  3. As a means of infiltration to allow drainage for e.g. wadi and garden paths.
  4. As a floor insulation on top of the soil as applied in ’t Centrum at KampC.

What makes shell insulation circular?

Teun: “Shells are the only insulation that can withstand moisture without being degraded. They are bio-ecological, are not modified, are not anchored/glued (loose shells) and are therefore easy to recuperate and reused for similar application. That’s what makes this a very circular product. In sustainable constructions you should use eco-friendly products with good insulating properties. Shells meet this demand.

It needs no explanation that they are natural and sustainable. Furthermore they are multifunctional. Shells occur in different forms and sizes. Smaller sizes are ideal for drainage, bigger versions are very heat insulating.

They can even protect the climate inside the habitat because they form a natural barrier between groundwater and the inside floors. People sensitive to fluctuations in humidity (reumatic and asthmatic patients) can breathe comfortably in every space.”

What is the insulation value of the shells?

Teun: “The Lambda-worth is 0.155W/m²K according to WTCB (Belgian Scientific and Technical Centre for the Construction Industry) and 0.106 Wm/m²K according to the Technical University of Delft.”

How and why are seashells used within ‘t Centrum?

Teun: “The seashell insulation is used as a floor insulation in ’t Centrum. The shells lay directly on the soil, the total shell package has a thickness of 60cm. A total of 440m³ of washed and sieved seashells (15-35mm) were used.

The shell insulation is circular and benefits the air humidity in the building. Odours, fungus, vermin or concrete rot have no chance. That’s because a layer of shells, contradictory to sand, is not capillary, it will not suck up moist. The shells will form a natural barrier between the groundwater and internal floor. The upper shell layer is entirely dry and the evaporation of groundwater will reduce significantly.

Where do these shells originate from?

Teun: “There is an endless supply of shells form the Northsea and the Eastern Scheldt. Shells are regrowable and are formed endlessly by marine molluscs.

The shells come in through controlled dredging of shells and shell sand from the Netherlands. They are harvested per ship by sucking them from the sea bottom in the Northsea, the Wadden Sea and Zeelandic waters.

Aboard they will pass through a sieve and will be washed up to two times. On shore they are sieved again and washed with fresh water. This way the remaining salt is washed out and the shells will not harm fauna and flora.”

More information:

’t Centrum is a pilot case within ProCirc ( Each pilot aims to reduce 20-25% raw materials, waste and CO2 emissions. These goals are, amongst other measures, met by the implementation of new green innovative solutions such as the use of seashells for insulation.