Is it necessary to install a vapor barrier before blowing?

In new buildings, the question does not arise as the DTU requires the implementation of tightness with Sd ≥ 18m. During renovation, the installation of a membrane is only mandatory in the case of a supporting floor made of small elements with tight joints (for example, wooden slats). Otherwise, this question refers to paragraph §4.3.1 of CPT 3647 regarding “Implementation of thermal insulation processes added to attic floors and lost attics …”. The requirements are a bit complex, but the more general case consisting of a ventilated tile roof, a flat western climate outside the very cold zone, and no distribution surface above the insulation, must be retained. In this case, the sum of the resistance to vapor diffusion of the support floor (ZDP) and the insulation (ZDI) must be> 3 m².h.mmHg / g. Just know that from R ≥ 6 m²K / W in Nita-Cotton, the ZDI alone exceeds the requirement. Therefore, the vapor barrier is not necessary.

Since when does NITA-COTON exist?

In 1992 RMT created its dry wool bleaching process. This opens the door to other specific applications and treatments (including flame retardants and fungi). Hence the first treated cottons are born. NITA-COTON as we know it today officially appeared on the day of its first European technical approval (ETA 10/0311) in 2010.

Can NITA-COTON be used in public buildings?

In accordance with paragraph §1 b) of article AM 8 of the fire safety regulations for establishments open to the public, all bio-based insulation and so-called “fuels” are perfectly usable as long as they are not in direct contact with the spaces. . of life and is placed behind the fire screens ¼ hour on the floor and wall and ½ hour on the ceiling. The use and characteristics of these screens (ex: BA13) are detailed in the guide for the use of combustible insulation in public buildings, which accompanies the document in annex II. (source:

What is the reaction to fire of NITA-COTON?

As with all materials subject to CE marking, reaction to fire is defined by the Euroclass. NITA-COTON benefits from a B-S2, d0 classification continuously certified by a third party according to system 1 of the CE marking, which represents the best possible classification for a bio-based material. Class B is defined as “non-flammable fuel” and “self-extinguishing”.

Can we use NITA-COTON on the walls?

The insufflation process is not yet relevant because it requires demanding machine characteristics. Thermally bonded panels and rolls are in the adaptation process and will be offered very soon.

During the renovation, should we remove the old insulation?

Since the coefficient of permeability to vapor diffusion is very low, there is no major problem in blowing NITA-COTON over old insulation. The real question is, what’s underneath? A permanent heat source such as a bulb or any other electrical element could, for example, not present any problems so far due to very low insulation. The additional insulation then causes a containment effect for this heat source and therefore a significant source of risk. Do you really want to cover rodent droppings or fungal growth forever? For various reasons like these, we recommend removing the old insulation.