ISOVER VARIO® intelligent humidity control and air tightness system for energy efficient, well insulated homes

Energy-efficient homes need, among other materials, various foils and membranes that provide airtightness, moisture protection and humidity control. For timber frame or any other type of wooden house, strict interior moisture control is all the more important because moisture can affect not only the insulation materials but also the wood that makes up the structure of the house. Saint-Gobain ISOVER, the Romanian market leader in thermal and sound insulation materials for the construction industry, has developed an intelligent system for humidity control and air tightness. ISOVER VARIO®. System provides active building protection by controlling humidity and air quality in buildings. It consists of a climate smart membrane with variable permeability and related accessories. The difference to a simple vapour barrier is that the ISOVER VARIO® membrane is hygroscopic, adapting its properties according to the humidity in the structure and the outside temperature. But before we say more about how the ISOVER VARIO membrane works and its advantages, let's see what a vapour barrier is.

What they are and why vapour barriers are used

Vapour barriers are membranes that are placed on the front side of the house insulation to prevent moisture in the air from passing through and condensing on the back wall. They are different from anti-condensation films which are put on the outside of the insulation, towards the roof, to stop moisture from reaching the insulation. Insulations are more or less permeable to the passage of vapour (there is a specific coefficient for each), depending on the type and density, but eventually they are permeated and when the vapour reaches a surface colder than 12°C, it condenses. The water droplets formed can enter the wood structure or insulation, create conditions for fungi and mould to grow and if no action is taken, wood and insulation can invariably be damaged. To prevent vapour from reaching these cold surfaces, vapour barriers should be installed.

An important differentiating parameter between the anti-condensation film and the vapour barrier is the vapour permittivity Sd. The unit of measurement is the metre, rather odd at first glance. The explanation is that the Sd value represents the equivalent vapour permeability of an air layer of the same thickness. Depending on this value, a distinction is made between condensation foils (Sd2m), mounted on the inside.

But let's get back to the dampness that occurs in houses. Where does it come from and why does it accumulate in indoor air? It's the result of our daily activities and our sweating and breathing, as well as the fact that structural wood continues to dry out, removing moisture. All this water in the form of vapour accumulates because houses are well insulated and airtight. This is why it is always recommended that in order to have an energy efficient and healthy timber frame house, there should be both architectural and structural design and installations. Both the insulation and the vapour barrier must be very accurately calculated and sized.

Simple vapour barriers are effective in winter, stopping moisture getting into insulation and wood, but can cause problems in summer. This is particularly noticeable on roofs, where wood that is not completely dry is sometimes used for the roofing. In summer, when temperatures are high, this water escapes from the wood and is prevented from passing through the foil, accumulating in the insulation. That's why smart membranes have emerged that behave differently depending on the temperature. One such membrane is ISOVER VARIO®, a vapour barrier film with variable Sd.

AdvantagesISOVER VARIO®

The ISOVER VARIO® system provides all-season moisture protection, preventing moisture from condensing on cold walls in winter and drying wood in summer. Adopting it increases the lifetime of the wooden structure and increases indoor air quality. At the heart of the system are innovative membranes ISOVER VARIO^® KM Duplex UV. Unlike ordinary vapour barriers, they allow moisture from damp wood to migrate inside the building in summer, preventing severe structural damage. This is made possible by the special structure of the membrane whose micropores close in winter, preventing moisture from escaping, and open in the hot summer months. During this period the amount of moisture passing through the film can increase 25 times. The film is made from a special polyamide, has no volatile organic compound (VOC) emissions and is food safe.

In addition to protecting wooden structures against damp and ensuring that the wood dries, ISOVER VARIO^® KM Duplex UV protects against wood preservatives, contributes to environmental protection (product with EPD environmental declaration) and improves indoor air quality (Class A+ for emissions according to the French classification system).

How to use the ISOVER VARIO® system

Fitting the ISOVER VARIO membrane^® KM Duplex UV must be carried out by professionals, on the inside of the insulation, continuously, on walls, floor, ceiling, roof. The correct functioning of the ISOVER VARIO® system depends on the correct use of the installation instructions and the use of the auxiliary materials that make up the system. These are:

• Isover VARIO® KB 1 - adhesive tape to make the joints of the membrane strips.
• Isover VARIO® Multitape - reinforced adhesive tape for sealing and fixing membrane penetrations.
• Isover VARIO® DoubleTwin - flexible, double-sided adhesive tape with high bonding strength. It is recommended for preliminary fixing of the membrane to a solid substrate.
• Isover VARIO® DoubleFit - elastic adhesive for making watertight joints between membranes and walls, boards or floors.

In addition to preventing moisture from escaping in winter and letting it in in summer, ISOVER VARIO® is used to provide airtightness, eliminate thermal bridges and eliminate air leakage through areas around exterior doors and windows, through the ceiling or through penetrations in pipes and electrical and thermal paths. Auxiliary materials ensure that the membrane is seamlessly joined so that air leakage is avoided and maximum energy efficiency of the building is achieved. Air tightness can be checked, the air tightness test is also known as the blower-door test. But we will talk about this on another occasion.