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Home Saint-Gobain Products and Solutions Product Selector Products Airtightness and Moisture management

Airtightness and Moisture management

Isover Vario KM Duplex is a high performance membrane unique in providing excellent levels of airtightness with unparalleled protection against moisture.


  • Improves the energy efficiency of the building by reducing heat loss through the building envelope to a tenth of that of a conventional house
  • Improves thermal comfort by protecting against leaky cracks and joints which invariably cause uncomfortable drafts
  • Ideal for use in low energy and Passive House constructions and buildings with mechanical ventilation and heat recovery systems


Why is airtightness important?

Only when the construction is airtight can warm air be retained within the building and cold air kept outside. Preventing unpleasant draughts means greater living comfort and increased energy efficiency, which in turn leads to lower heating costs. Airtightness also protects the building fabric against damage, helping to maintain its appearance and extending the building’s life.


Energy efficiency

The trend towards increased energy efficiency has led to house constructions that are thermally and economically optimised, similar to those defined in the Passive House standard. Increasing the thermal integrity of a building can reduce transmitted thermal loss, i.e. heat lost through the building envelope, to a tenth of that of a conventional house.


Thermal comfort

As we spend more and more time indoors, a comfortable interior climate has become increasingly important. It is no longer enough just to have basic protection against cold or heat, families today expect a constant, comfortable living environment and fresh air all year round. This, in turn, makes stringent quality demands on the quality of design and construction of a building. As well as having adequate thermal insulation, the building shell must be airtight to prevent the uncontrolled flow of air in and out of the building. Leaky cracks and joints will invariably cause uncomfortable draughts.


Protecting the building fabric

Leaks are a potential cause of damage in a building. When damp, warm air moves from the interior of a room through gaps and cracks into the colder areas of the building, the water vapour it contains can condense into water. This condensation provides an ideal habitat for moulds and other fungi. Depending on the location and the size of the leak, the material affected can therefore suffer damage. In addition, when moisture penetrates insulation material its insulation performance can be reduced by up to a sixth, when compared to dry material. This reduction in thermal performance leads to further dampness accumulating in the construction, setting in motion a chain reaction that invariably leads to serious damage. An airtight building shell, without leaks, prevents this process and helps to ensure the longevity of the building fabric.

Companies specialising in Airtightness and Moisture management

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