Recycork – Upcycled Cork Tested in a Floor System

Recycled cork-stopper granules applied loose and without any supporting structure: circular utopia or real technical breakthrough? And what if this approach opened the door to a more rational and sustainable way of designing our floors by making use of resources already available?

The floor system in detail

For several months now, Natura Mater and Earth Plant & Fiber (EPF) have been jointly studying Recycork, a bio-based and circular insulation material derived from recycled cork stoppers.

The objective: to test the application of loose recycled cork, without any complementary structure, within a self-supporting floor system.

A simple and reversible approach that opens the way to new, more sustainable construction practices.This system is being implemented for the first time under real-life conditions as part of the Greenhouse project, and will be subject to detailed technical and environmental monitoring by Buildwise in the coming months.

Initiated by Earth Plant & Fiber, Greenhouse is a demonstrative construction site that brings together several circular approaches: prefabricated timber structure, reused glazing, bio-based insulation… and now a 100% circular floor system.

The site is overseen by Otik architecture and executed by the company Eltherm.

The Greenhouse project in Tienen

A bio-based resource at the heart of the circular economy.

Every year, around 90 tonnes of natural cork are collected in Belgian recycling parks, sorted, cleaned, and ground into granules. The result: Recycork - a bio-based, local, and circular insulating material produced from a waste stream that is almost always incinerated.

Its strengths: low carbon footprint, good thermal inertia, moisture resistance, and ease of reuse.

Beyond its environmental dimension, the sector also generates strong social impact by creating jobs for people in reintegration programmes. Recycork is produced by De Vlaspit, a Flemish non-profit active in the social economy.

A collaboration anchored in the Belgian bioeconomy:

Earth Plant & Fiber (EPF) is a coalition of actors engaged in the Belgian bioeconomy. Its mission: to create bridges between producers, researchers, architects, and companies in order to accelerate the adoption of circular and bio-based materials.

As an actor committed to the transition toward sustainable construction, Natura Mater is an active member of the coalition and frequently collaborates with the other members on material development - including technical and environmental consulting, and contributions to concrete projects such as BOOST Recycork, a development programme aimed at improving the technical performance of the product and redefining its applications.

Its objectives include:

• Identifying relevant applications for Recycork

• Conducting tests to quantify technical advantages and provide guarantees to project owners

• Developing a clear distribution strategy based on collection, transformation, and waste-stream management

• Exploring certification pathways and integrating the product into PEB/EPBD databases

Why test Recycork in a floor system?

Thanks to its properties, cork offers a wide range of possible applications - coating, blown-in insulation, mats or insulation boards, and more.In our study, we focused on two concrete implementations: loose-fill insulation between structures (already tested with very positive results) and, as explored here, the use of loose insulation within a floor or slab system.

This latter application had never been implemented on a construction site before. However, tests carried out by researchers at KU Leuven have demonstrated encouraging performances — notably a deformation limited to 3 mm under a 3 kN load - confirming the technical potential of this approach.

Key advantages:

• Recycork has a favourable thermal conductivity (0.047 W/mK), comparable or even superior to certain insulating screeds or other bio-based materials such as hemp-lime.

• Conventional materials used for this type of application - PUR, EPS - are generally very impactful environmentally and non-recoverable. The carbon benefit of Recycork is therefore significant: 2.7 kgCO₂e/m² compared to 30–71 kgCO₂e/m² for classic solutions.

• Technical systems (pipework, cabling) can be integrated directly into the layer of recycled cork, making the system simple, modular, and fully reversible.

• Recycork is lightweight, non-toxic, odourless and produces no dust - much to the delight of installers.

The floor build-up, in detail:

The experiment covers almost the entire ground-floor surface. It consists of:

• a layer of insulating seashells (35 cm)

• loose Recycork as intermediate insulation (10 cm)

• a concrete screed with embedded underfloor heating (8 cm)

The layers are separated only by a vapour-open membrane, allowing easy dismantling and future reuse.Initial on-site feedback is encouraging: Recycork is easy to spread and level, produces no dust or odour, exhibits low and uniform settlement, and its low weight makes handling easier on site.

However, one constraint arose during installation: the localized displacement of granules under workers’ footsteps. Although the granules support distributed loads well, their loose application complicates movement on site as well as the installation of the upper-layer elements.

To solve this issue, a honeycomb structure was added to stabilise the surface during this phase. This lightweight structure simply stabilizes the insulation to facilitate the installation of the underfloor heating system and the pouring of the screed.

This temporary solution opens the door to other stabilisation strategies currently being explored for future projects. This is the value of full-scale testing: recognising the limitations of the system and developing solutions for future applications..

A project under technical monitoring:

Given the singular nature of this pilot project and the unique opportunity to test the performance of several bio-based materials in situ, Buildwise joined the experiment by installing sensors at the heart of the floor system - ensuring continuous technical monitoring over the coming months - to assess changes in humidity levels, mechanical stability, and the material’s durability under real conditions.

This monitoring will allow us to better understand the behaviour and performance of this circular, innovative, and promising floor system.

Perspectives and conclusion:

The Greenhouse construction site will continue until the end of 2025. In the meantime, several actions are underway: collecting and analysing sensor data, updating the Recycork technical sheet, and carrying out an awareness campaign to increase cork collection at the regional level.The objective is to use this resource on a larger scale in the future.

For Natura Mater and EPF, the project illustrates the current challenges of sustainable construction: regulatory complexity, certification costs, and the need for appropriate support for local and social initiatives. But it also reflects a positive dynamic: a sector that is organising itself, innovating pragmatically, and contributing concretely to reducing the carbon footprint of buildings through recycled and circular materials - with a healthy dose of innovative spirit.

A warm thank you to our partners in this project and to the open, ambitious, and collaborative spirit of all contributors, including Rein Dessers (EPF and project owner), Roel Coose (Eltherm), Sarah Beuls (OTIK), and the entire Recycork team.Natura Mater is proud to contribute to this collective project, alongside committed actors, to gradually build a future where sustainable construction goes hand in hand with inclusion, circularity, and local anchoring..