Parex Lanko gets green with her lime and hemp coating
Batirama.com 23/10/20190How does one of the major players in the supply of coatings and mortars based on hydraulic cement carry out its “biosourced” revolution? Answer: by leveraging its R&D resources.
This is the story of a €4.4 million industrial project (including a €1.97 million grant from Ademe) which came to fruition after five years of research and development in the laboratory of Parex Lanko.
Named Parnatur Corps d’Enduit Chanvre, the spray mixture, launched on the market this October, is made up of a binder based on lime and chènevotte. This interior and exterior insulation material is intended for old buildings; it is also suitable for new construction on materials sensitive to water vapor transfer, such as brick.
Suffice to say that this shift towards bio-sourced has everything to give cold sweats to the subsidiary of the Sika group, which is more accustomed to hydraulic binders.
Insulate traditional stone, earth, half-timbered walls
Launched in 2013, the R&D project follows the publication of the so-called Atheba sheets (Thermal improvement of old buildings) established in 2010 by the Creba. Vernacular materials require solutions that take into account both thermal insulation and vapor transfer. Parex Lanko notes that its catalog does not offer products suitable for the insulation of traditional walls in stone, earth, half-timbered, etc.
The manufacturer's ambition, explains Sonia Yansi, marketing manager at Parex Lanko, is to develop an improved formulation compared to available bio-based products: with a lower density, lower thermal conductivity and more insulating. In addition, to bring productivity on site, it had to be mechanized, projectable.
Over the years, after multiple formulations and test sites, Parex Lanko decided at the end of 2018 on a complete concept which is based on a bio-based product, specific equipment and safeguards based on training.
This insulation should be laid in several layers up to 8 cm thick plus coated with a waterproofing mortar.
A product concept + installation
The product is a two-component product, a lime-based binder (on which Parex Lanko has filed two patents) and a hemp shiv – hemp straw – cut to a very precise grain size by the supplier, Chanvrière de l'Aube .
The chosen formula is 10 kg of hemp for 25 kg of lime-based mortar, delivered in two 12.5 kg bags deemed easier to handle, all mixed in 52 to 60 l of water depending on the temperature and the degree of firmness of the pass. The material formed by mixing meets the Karibati biosourced label, namely a hemp volume of 70% for a share of 25% by weight.
This coating is based on a mechanized application which has also been the subject of a patent. If 80% of facade spraying machines can be used, on the other hand, they must be "customized" with three specific parts to use the mixture.
This insulation should be laid in several layers up to 8 cm thick plus coated with a waterproofing mortar.
A controlled grain size
First, the jacket, a mechanical part at the outlet of the machine, is modified to avoid “straining” the mixture before it is introduced into the pipe.
Because of the presence of hemp, the first tests had indeed revealed a risk of clogging: only the mortar came out of the nozzle, and the plant load was found to be absent from the projected material...
Parex Lanko solved this sticking point by playing on two levers: the controlled particle size of the shiv and the internal design of the jacket.
Second part suitable for spraying: the 30 m hose with a diameter calibrated for this mixture. The third is the projection lance, equipped with a tapered nozzle 16 mm in diameter at the outlet. The whole has the advantage of ensuring a projection practically without any rebound effect and a maximum yield of the mixture. The work can be carried out at the rate of 70 m² per day.
The grain size of the hemp has been determined by the developers of the product for spraying with a lance.
The outlet of the spraying machine is equipped with a jacket that eliminates the spinning of the mixture under the pressure of the piston.
A light and insulating product
The proposed hemp coating is applied in a thickness of 2 to 8 cm thick, both outdoors and indoors. The recommended laying method is by thin passes of 2 cm, fresh on fresh up to 3 passes per day and each drawn with a ruler. Coats should be spaced 24 to 48 hours apart to optimize adhesion.
"Training the ruler is important," explains Valdemar Limoes, mason specializing in biosourced materials based in Île-et-Vilaine. The straighter and thicker the material, the stiffer it is; the application of the coats on a first very dry pass avoids cracking. » Outdoors, the material dries at the rate of 2 cm per week: indoors, this time doubles.
The material is very flexible (30 MPa in bending) and not very resistant to compression (0.3 MPa). It must be coated and is compatible with Parexal or Heritage type waterproofing coatings.
The mixture is designed to be prepared in a jetting machine.
A formula established after years of research
After years of research, the Parex Lanko laboratory technicians have succeeded in establishing a formula that goes well beyond the initial specifications.
Its density is 310 kg/m³, its thermal conductivity is 0.066 W/m.K – at 23°C and 50% RH, below the target of 0.1 –, its thermal resistance is 1.33 m² .K/W for 10 cm thickness, its diffusivity of 0.179 mm²/s, its effusivity of 156 J/K.m².s1/2, its permeability µ is equal to 4.2 (for a usual level of 8 for lime plasters) and its hygrothermal performance (known as MBV) of 2.9 g/m².%RH.
Clearly, its insulation capacity makes Parex Lanko say that 5 cm of material halves the loss coefficient of a wall, that it allows a long thermal phase shift (3 h 15 for 6 mm) and that it is very permeable to water vapour. This product already has an environmental and health declaration sheet (FDES) which sets its total CO2 emissions at 6.4 kg/m² for 8 cm of thickness.
06 Parnatur– The lance is designed to minimize material rebound. The mortar is applied in several thin coats fresh on fresh. A delay between two coats is 24/48 hours.
For trained applicators
Despite these qualities, this supplier wants to avoid deviations and counter-references. Parex Lanko will be accredited to train installers and issue them with a certificate of proficiency; installers already applying similar products (Saint Astier, etc.) and recognized as such by their insurer are exempt.
Free of charge, this procedure will be compulsory in order to acquire the essential installation accessories. This supplier thus wishes to develop a network of 50 to 70 referent applicators from 2020. With the key issue of growth in this bio-based segment, and image of innovation, in particular with project managers.
Anne Daubresse, head of the prospective, methods and training division at Parex Lanko. “The installation accessories will be accessible to companies that have been trained in installation and have the certificate of aptitude. Parex Lanko is accredited for this approach, which will be carried out by around ten trainers. »
Source: batirama.com / Bernard Reinteau
