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

Energy efficient houses need, among other materials, various foils and membranes to ensure airtightness, damp-proofing and moisture control. In the case of timber frame houses, timber frame houses or any other type of wooden house, strict control of interior humidity is all the more important because moisture can affect not only the insulation materials, but also the wood that forms the structure of the house. Saint-Gobain ISOVER, the Romanian market leader in thermal and phonic 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 intelligent variable permeable membrane and related accessories. The difference from a simple vapor barrier is that the ISOVER VARIO® membrane is humidity-adjustable, adapting its properties according to the humidity in the structure and the outside temperature. But before we tell you more about how the ISOVER VARIO membrane works and its advantages, let's see what a vapor barrier is.

What vapor barriers are and why they are used

Vapor barriers are membranes that are placed on the house side of the insulation to prevent moisture in the air from passing through and condensing on the back wall. They are different from anti-condensation sheets 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 vapor (there is a specific coefficient for each), depending on their type and density, but they are eventually permeated and when the vapor reaches a surface colder than 12°C, it condenses. The water droplets formed can penetrate the wood structure or insulation, conditions are created for fungi and mold growth, and if no action is taken, the wood and insulation can invariably be damaged. To prevent vapors from reaching these cold surfaces, vapor barriers should be installed.

An important separating parameter between the anti-condensation film and the vapor barrier is the vapor permittivity Sd. The unit of measurement is the meter, rather strange at first sight. The explanation is that Sd is the equivalent vapor permeability of an air layer of the same thickness. Depending on this value, a differentiation is made between condensation foils (Sd2m), mounted on the inside.

But let's get back to the damp that occurs in homes. Where does it come from and why does it accumulate in indoor air? It's the result of our daily activities and our perspiration and breathing, as well as the fact that structural wood continues to dry out, removing moisture. All this water in the form of vapor 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-framed house, there should be both architectural, structural and plumbing design. Both the insulation and the vapor barrier must be very accurately calculated and sized.

Simple vapor barriers are effective in winter, stopping moisture from 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 roof framing. In the summer, when temperatures are high, this water seeps out of the wood and is prevented from passing through the foil, accumulating in the insulation. This is why smart membranes have emerged that behave differently depending on the temperature. One such membrane is ISOVER VARIO®, a vapor barrier film with variable Sd.

Advantages ISOVER VARIO®

The ISOVER VARIO® system provides all-season moisture protection, preventing moisture from condensing on cold walls in winter and drying the wood in summer. Its adoption extends the life 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 vapor barriers, they allow moisture from damp wood to migrate into the building in summer, preventing severe structural damage. This is possible thanks to the special structure of the membrane whose micropores close in winter, preventing moisture from escaping, and open in the warm summer months. During this period the amount of moisture passing through the film can increase by up to 25 times. The film is made from a special polyamide, has no emission of volatile organic compounds (VOCs) and is food safe.

In addition to protecting wooden structures against moisture and ensuring wood dryness, ISOVER VARIO^® KM Duplex UV protects against wood preservatives, contributes to the protection of the environment (product with EPD environmental declaration) and improves indoor air quality (A+ class 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, floors, ceilings, roofing. The correct functioning of the ISOVER VARIO® system depends on following the installation instructions and the use of auxiliary materials that make up the system. These are:

• Isover VARIO® KB 1 - Adhesive tape for seaming the membrane strips.
• Isover VARIO® Multitape - Reinforced adhesive tape for sealing and fixing membrane penetrations.
• Isover VARIO® DoubleTwin - Double-sided, flexible, double-adhesive tape with high adhesive 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 seal, 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 routes. Ancillary materials ensure that the membrane is perfectly bonded so that air leakage is avoided and maximum energy efficiency of the construction is achieved. Airtightness can be checked, the airtightness test is also known as the blower-door test. But more on that later.