Stock material or miscellaneous articles – Structurally defined web or sheet – Including aperture
Patent
1985-02-20
1986-01-28
Van Balen, William J.
Stock material or miscellaneous articles
Structurally defined web or sheet
Including aperture
4283166, 428913, B32B 310
Patent
active
045670803
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a vapour barrier comprising a layer of a vapour-tight (vapour impervious) material connected with a layer of water absorbing material, openings permitting the passage of vapour and water being provided in the layer of vapour-tight material.
The invention is chiefly directed to a vapour barrier for use in connection with roof constructions comprising a vapour-tight outer covering.
In roof construction with such a vapour-tight outer covering, e.g. one or more layers of roofing felt, when the outer temperature drops, a condensation of water vapour and thereby an accumulation of moisture may take place on the underside of the outer covering, unless special precautions are taken to avoid that moisture saturated air gets into contact with the underside of the cold outer covering.
In roof constructions comprising cavities wholly or partly filled with a layer of porous heat insulating material, a vapour-tight foil is frequently interposed between the layer of heat insulating material and the underside of the roof construction, e.g. a ceiling lining, in order to prevent an accumulation of moisture in the zone between the ceiling lining and the outer covering. However, it is impossible in practice to prevent the occurrence of leakages in such a vapour-tight foil, through which leakages moisture loaded air penetrates into the zone between the vapour-tight foil and the outer covering.
To remove the moisture penetrating through the vapour-tight foil, the Danish building regulations prescribe that roof constructions of the kind described should be ventilated. In the case of smaller roof areas this requirement can normally be fulfilled by providing ventilation openings in the roof overhang, which openings communicate with the interior of the roof construction.
To obtain a suitable ventilation of larger roof areas it will usually be necessary to mount ventilating means, such as ventilating hoods, which are connected with the interior of the roof construction.
When using ventilating hoods for the venting of roof constructions in which the roof covering is completely airtight, such as a roofing felt covering, the flow of air, and thereby the flow of moisture through the leakages of the vapour-tight foil will be considerably increased, and the ventilation hoods may in such cases strongly aggravate the moisture problems rather than alleviating them.
In the Danish patent specification No. 87,317 there is disclosed a covering for application to the inner side of walls consisting of a water and a vapour impervious material, such as a ship's side or a wall of an airplane, the said covering consisting of a layer of heat insulting material applied to the inner side of the ship's side or airplane wall and being provided on its inner side with a perforated water vapour arresting layer, wicks being provided in the perforations of the water vapour arresting layer. These wicks serve to conduct condensed water formed in the interspace between the ship's side or the airplane wall and the perforated water and vapour arresting layer out of the said interspace and into a moisture distributing layer applied to the inner side of the water and vapour arresting layer and from which it can be removed by evaporation.
If a covering of the above mentioned type were used as a vapour barrier in a roof construction having a watertight outer covering, it would offer a too small resistance to diffusion of water vapour to prevent that the amount of moisture, which in the cold part of the year diffuses through the water and vapour arresting layer and is condensed in the zone between this layer and the vapour-tight roof covering, will exceed the critical value for rot and fungal attack, and to prevent dripping before the moisture is evaporated when the accumulated moisture is driven out of the interspace between the two layers during the hot part of the year.
It is the object of the invention to provide a vapour barrier of the kind mentioned in the introduction, which offers a sufficiently high resistance to diffusion of water vapou
REFERENCES:
patent: 3253598 (1966-05-01), Spanel
patent: 3881489 (1975-05-01), Hartwell
V.I.K.-Consult ApS
Van Balen William J.
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