The construction industry is starting to go green. Between the search for new ecological materials and more efficient construction methods, the sector’s objective is clearly to start building in an environmentally friendly way. Wood-based concrete is among the greener alternatives that are emerging to replace high carbon footprint construction materials. The French company CCB Greentech has specialized in this new resource. Construction group Lafarge has even invested in the company.
Is wood-based concrete the new wonder building material? In any case, it’s made of cement, water, and wood (80%) and is expected to be an alternative to many carbon-intensive materials.
French company CCB Greentech develops the TimberRoc® technology that enables precast load-bearing walls and slabs made of wood-based concrete. According to them, their wood-based concrete has a negative carbon footprint. This could make building construction greener.
We spoke to Caroline Gérard, Marketing Director, to find out more about this revolutionary product.
Pulpwood is a timber that has good intrinsic characteristics but is not physically as beautiful as the lumber that is used to make furniture and timber frame houses. CCB Greentech buys pulpwood logs from PEFC-certified foresters located in France’s Rhône Alpes region, close to their production plant. They transform them into wood granulate. Then they add an additive, water, and cement for strength and durability, and it is ready to be used to produce wood-based concrete.
Mrs. Gérard did not tell us in detail what kind of additive they are specifically using to make the wood granulate.
Their final wood granulate can then be sold exclusively to precast concrete manufacturers who will use it to produce slabs and walls, both load-bearing and not. Precast wood-based concrete walls and slabs are intended for the construction of low-energy and passive buildings.
CCB Greentech’s wood-based concrete contains 80% of wood by density. And according to the company and an FDES (Environmental and Health Data Sheet), their material has a negative carbon balance.
“During their growth, trees absorb C02, thanks to photosynthesis, and store it in their wood cells. As our wood is encapsulated in cement for the whole life of the product, it does not release any C02. So by using pulpwood to produce wood-based concrete, we trap this carbon in the walls, slabs… And as the cement we use required fewer C02 emissions than the wood we use absorbed, our carbon balance is distinctly negative. We can go up to -70 kg of CO2 emitted per m², depending on the thickness of the wall and the construction method.”
Additionally, all the pulpwood is used so no waste is generated.
The company says its wood-based concrete meets the 3 requirements of the French environmental regulation RE 2020 (carbon impact, energy performance, and summer comfort in the building).
“Our wood-based concrete surpasses on all these points many existing materials such as bricks, concrete, and wood frames. Why? Because it offers good thermal insulation and very high perspiration and a huge thermal phase shift of more than 18 hours for a wall that’s 30 cm thick. This means that the outside temperature will take more than 18 hours to pass inside the wall. Moreover, we have a thermal damping rate that is higher than 96%. Whether in winter with negative temperatures or in summer with very high temperatures, the heat or cold will take so long to pass inside the wall that the temperature variation inside the building will be very low.”
Wood-based concrete is a porous material with breathable and water vapor diffusion properties. This ensures control of hygrometry in the thickness of the walls, thus eliminating possible condensation disorders. It also offers a natural regulation of the humidity of the interior air, contributing to the energy performance of the building in winter as well as in summer. It also provides good fire resistance.
Combined with other efficient materials and construction methods, wood-based concrete could make air conditioning and heating obsolete.
The fact that it could replace traditional concrete is interesting. Concrete uses exhaustible resources such as gravel and sand and has a massive carbon footprint. But wood-based concrete cannot replace traditional concrete everywhere.
For the moment, the company recommends that precast wood-based concrete manufacturers make load-bearing walls in wood-concrete only up to 3 floors. Beyond 3 and up to 10 floors, load-bearing walls must also incorporate reinforced concrete and only the non-bearing walls can be fully in wood-based concrete.
Mrs. Gérard also adds that the wall thickness is similar to bricks or concrete blocks but that it is more important than with wood frames.
60 buildings have used their wood-based concrete so far: apartment blocks, single-family houses, offices, restaurants…
Regarding the price, wood-based concrete is 15% to 20% more expensive than conventional precast concrete.