The durability of humidity-variable vapour check (Oceania: vapour control; North America: vapor retarder) and airtight membranes needs to be tested and confirmed – this has been stipulated by the German wood preservation standard DIN 68800-2 since 2012. This standard has been adopted by the construction inspection authorities in Germany, which means it is not just a recommendation, but instead forms part of building law and is thus legally binding. DIN 68800-2 explicitly demands verification of the ageing behaviour of vapour checks with humidity-variable diffusion resistance.

If this verification cannot or has not been carried out, a vapour check that is described as a ‘humidity-variable vapour check’ is a vapour check with constant diffusion resistance (sd value) from a legal viewpoint and it may only be used as such. CE marking in line with EN 13984 does not indicate that the long-term humidity-variable performance has been verified. The background to this is that the European standard does not deal with the concept of humidity-variable vapour checks and thus does not specify testing methods for determining humidity-variable behaviour or for demonstrating resistance to ageing.

This verification can be provided in the form of a European Technical Assessment (ETA), for example.

If humidity-variability is not governed by an ETA, for example, the vapour check in question is not to be regarded as a humidity-variable vapour check. In this case, the use of this type of membrane as a humidity-variable vapour check would violate the European Construction Products Regulation. This could lead to recourse claims from building clients who are well-informed.

The same applies if the use of a humidity-variable vapour check is demanded in a specification or is part of a quotation by a company that carries out building work. This requirement can only be fulfilled by a humidity-variable vapour check with verified long-term performance.

INTELLO and INTELLO PLUS are the first humidity-variable vapour check to have their long-term performance confirmed by official technical approval. The ETA independently confirms the resistance to ageing of these two INTELLO membranes for a period of at least 50 years.

All of the tests for this technical approval were carried out independently by an accredited testing institute. This accreditation is important because the testing institute is in turn monitored independently by the German Accreditation Council, which ensures the independence and reliability of the test results.

INTELLO works on winter building sites

With INTELLO and INTELLO PLUS from pro clima, winter building sites are not a problem! However, having the right hydrosafe value is important here. The hydrosafe value specifies how well sealed a humidity-variable vapour check still is at an average humidity of 70%. Average humidity of 70% will be present if there is 90% indoor air humidity and 50% humidity in the space between the rafters, for example – these values could be achieved while walls are being plastered or screed is being installed.

According to the 70/1.5 rule, a hydrosafe value of sd = 1.5 m is sufficient to keep the increased humidity that results from construction work out of a given structure. The 70/1.5 rule is derived from DIN 68800-2. Both INTELLO and INTELLO PLUS have a hydrosafe value of over 2 m, which is significantly above the requirement of sd = 1.5 m. However, the hydrosafe value should not be over 2.5 m, as otherwise the drying out of moisture that has penetrated into a structure in an unforeseen manner can be hindered.


The first ever humidity-variable vapour check membrane, pro clima’s DB+, was developed in the early 1990s with the aim of ensuring a high level of moisture protection during the construction phase and after buildings have been completed too. DB+ has been systematically refined to produce INTELLO and INTELLO PLUS. Millions of square metres of these membranes have been successfully installed on building structures. With INTELLO, INTELLO PLUS and DB+, building components are protected both during and after the construction phase.

Vapour check membranes do not work like a cactus, which closes its pores when it is cold and opens them when it gets warm

Humidity-variability must work when it is hot and when it is cold too! Otherwise the membranes cannot be used to protect building components with an indoor climate that remains roughly constant. In the case of ‘looped’ installation to create troughs for the insulation (i.e. installation of airtightness as part of roof refurbishment from the outside), it is also important that the membranes promote drying out on the outside, which may be cold. Membranes that are dependent on cold/hot will always lead to damage to structures. Depending on the temperature, drying out may not be possible. In addition, membranes with pores are not airtight!

Water regulation in cactuses has little in common with the functioning of a vapour check. Cactuses are succulent plants (water-storing plants). They can prosper in regions with low precipitation thanks to their large capacity to store water. Like most other plants, cactuses take up water through their roots and store it internally. Cactuses generally grow a flat root system with a wide reach. Their rate of water loss (through evaporation) is very low. They give off very little water through their relatively thick skin and their small spines. Water take-up (through roots) and evaporation (through spines) thus occur at different locations in the case of cactuses. There is no intelligent membrane process at work in the skin of cactuses.

INTELLO offers greater reliability than vapour retarders with a direction-dependent sd value

INTELLO and INTELLO PLUS ensure a high degree of protection against damage to structures. With their perfectly balanced diffusion behaviour, they ensure that structures will be particularly robust and well-protected. In winter, both membranes have a very high diffusion resistance and provide optimal protection to insulation materials against mould and damage to structures. In summer, they can become extremely permeable if necessary. In this way, moisture that has entered into a building component in an unforeseen manner can dry out again properly. This principle has proven itself in practice over more than 20 years and for many millions of square metres of installed INTELLO and INTELLO PLUS.

In contrast with membranes with direction-dependent diffusion resistance, humidity-variable INTELLO/INTELLO PLUS cannot be accidentally installed the wrong way around. These membranes offer excellent protection against damage to structures in both directions – during the construction phase and also for the whole service life of the building.

DASATOP is pro clima’s membrane for ‘looped’ installation to create troughs for the insulation (i.e. installation of airtightness as part of roof refurbishment from the outside). Its humidity-variable diffusion behaviour is ideal for this application. DASATOP too cannot be accidentally installed the wrong way around with regard to its moisture regulation behaviour. Thus the membrane does not need to be turned over. It can be installed directly from the roll. This avoids subsequent damage and/or the costs associated with installation errors of this type. The fact that DASATOP is not direction-dependent makes it easier to install properly.

With an sd value > 2 m, DASATOP prevents dampness in insulation materials in roof zones containing insulation. At the same time, DASATOP can be as permeable as a modern underlay membrane (sd value = 0.05 m) close to rafters. In this way, moisture can dry out in an almost unhindered manner.

The properties of pro clima membranes are tailored for their recommended applications. This ensures maximum protection against damage to structures in all cases. Installation is also easy and cost-saving (e.g. due to lack of glare and good malleability) for all structures. For this reason, we supply DASATOP, INTELLO and INTELLO PLUS. After all, a membrane than can do a little of everything will be a master of no single task!

Please contact us if you have any questions on the behaviour, planning or installation of INTELLO and INTELLO PLUS. The engineers who work on pro clima’s Technical Support or your local pro clima representative will be happy to support you with their specialist knowledge and practical experience.

Long-term effectiveness – tested and confirmed