60% and 70% Rule
The pro clima Rule for New Buildings and Construction Time
In times of improved levels of airtightness with associated higher atmospheric humidity in new buildings made of masonry, diffusion resistance to cater for increased relative atmospheric humidity becomes an important factor, although for climates of high humidity.
New Buildings: The 60/2 Rule
(equivalent to 60/1.65 US perms or 60/10MNs/g)
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The internal relative humidity in new buildings is high due to the construction work recently completed as well as the short time of occupation. The diffusion permeability of a vapor/vapour retarder should be designed in such a way that even at 60% mean relative humidity the sd-value is above 2m (mvtr of 60/10MNs/g) respectively below a permeance of 60/1.65 US perms in order to adequately protect the construction from moisture.
At a relative humidity of 60% INTELLO® has a sd-value of 4m (a mvtr of 20MNs/g respectively a permeance of 0.83 US perms) and meets this demand easily.
Construction Time: The 70/1.5 Rule
(equivalent to 60/2.2 US perms or 60/7.5MNs/g)
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During the construction period after having plastered or installed a screed the relative humidity in a building is very high. At a mean relative humidity of 70% the diffusion permeability of a vapor/vapour retarder should be above a sd-value of 1.5m (mvtr of 7.5MNs/g) respectively below a permeance of 2.2 US perms in order to protect the construction against excessive entry of moisture from the building site and from mould growth.
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INTELLO® vapor/vapour retarder exceeds the requirement of the 60% and 70% rule by far.
Thus the Constructions in wet or humid rooms in residential buildings like bathrooms and kitchens are reliably and safely protected even if subjected to increased humidity.
Generally, building moisture should quickly escape from the structure via open windows. Dehumidifiers can speed up this process during the winter.