AN EXTERNAL INSULATING LAYER

Abstract: An external insulating layer of mineral fibre sheets which each comprises a layer of mineral fibres bonded together by a binder and which is on the outer side of the insulating layer provided with a fibre binding surface layer having an air flow resistance of from 0.25 to 8.0 N.h/m<3>.

Description: An external insulating layer. The present invention relates to an external insulating layer of mineral fibre sheets each comprising a layer of mineral fibres v f 5 bonded together by a binder. DK patent specification No. 141,736 discloses a process for provid¬ ing roofs comprising a waterproof membrane with an external insula¬ tion. In this known process a layer of binder-containing mineral 10 fibre sheets is placed on top of the waterproof membrane of the roof, said sheets being provided with a dampproof film on the side facing the waterproof membrane of the roof. The dampproof film prevents water entering in between the insulating sheets and the waterproof membrane of the roof from evaporating and diffusing up 15 through the mineral fibre sheets and thus deteriorating their insulating power. DK patent specification No. 143,574 discloses a further development of the process described above wherein a layer of mineral fibre 20 sheets is placed on top of the waterproof membrane of the roof, said sheets being covered with a dampproof film on the side facing the waterproof membrane of the roof and on a portion of the sides of the mineral fibre sheets. 25 It is a serious drawback of external roof insulating layers and other external mineral fibre insulating layers of the kind disclosed above that the binder which bonds the mineral fibres together is decomposed under the influence of the sunlight and in particular ultra violet rays in the surface layer of the mineral fibre sheets. 30 Thus mineral fibres are loosened and consequently the heat insulat¬ ing power of the mineral fibre sheets is reduced. Such loosening of mineral fibres from an external pitched roof or an upright wall of the kind described above may cause the thickness of 35 the insulating layer to be reduced by about 1 mm a year. Furthermore, the sunlight may cause decomposition of the mineral oil which is often added to mineral fibre sheets of the kind described above in order both to reduce generation of dust during the manufacture of the mineral fibre sheets and to increase the hydrophobicity of the mineral fibre sheets. The decomposition of the mineral oil may thus result in a reduction of the hydrophobicity of the mineral fibre sheets and hence in an increased evaporation of water and consequently a reduction in the heat insulating power of the mineral fibre sheets. GB patent specification No. 2,107,371 describes mineral fibre sheets which are i.a. intended for the formation of an external insulating layer on houses, at least the one side of said mineral fibre sheets having been rigidified by coating of the fibres with a binder in such a manner that the porosity of the mineral fibre sheets and consequently also their low resistance to the diffusion of vapour are maintained. Attempts to use such surface-treated mineral fibre sheets for the construction of external roof insulating layers have proved that under the influence of a vacuum generated by strong winds the sheets are liable to loosen from the roof and blow away. It is the object of the invention to provide an external insulating layer of the kind described in the introduction which is both weatherproof and less susceptible to be torn away when subjected to the influence of strong winds than the known external insulating 1ayers. This object is obtained with the insulating layer according to the invention which insulating layer is characterized in that the mineral fibre sheets on the outer side of the insulating layer, are provided with a fibre binding surface layer having an air flow resistance of from 0.25 to 8.0 N-h/m 3 . The invention is based on the discovery that by use of such mineral fibre sheets for the formation of an external insulating layer, the difference in pressure on opposite sides of the sheets are rapidly compensated for, and thus the propensity of the sheets to loosen from the support is reduced simultaneously with the surface of the sheet being reinforced to such an extent that said loosening of fibres from the sheet is minimized. Accelerated experiments with the external insulating layers accord¬ ing to the invention have shown that over a period of 25 years the mineral fibre release from such layers is minimal when they are exposed to climatic influences and at the same time the heat in¬ sulating power of the layers remains substantially unchanged. A further advantage of the insulating layer according to the inven- tion is that it is resistant to damage occurring during mounting of the insulating layer and that it tolerates moderate walking without being damaged and that the insulating layer exhibits a considerable sound insulating power. The air permeable surface layer may be a porous coat of paint which is formed by applying a coherent coat of paint to the one side of a mineral fibre sheet and by optionally drawing air through the coat of paint and the sheet before the coat of paint is dried. The application of the coat of paint may e.g. be carried out by means of anti-setoff rollers whereby a suitable penetration depth of e.g. 3-4 mm can be obtained. This application method is suitable in connection with water-based paints, e.g. paints based on a polyvinylacetate binder and a pig¬ ment, such as a dolomite pigment. The surface layer may also be obtained by using paints based on organic solvents, such as toluene, white spirit and alcohol, and in that case the application of the coat of paint on the mineral fibre sheet surfaces may conveniently be effected by means of a varnish coat apparatus or conventional spray painting equipment as said paints due to their low surface tension are absorbed in the surfaces of the mineral fibre sheets under the influence of capillary forces. Both by using water-based paints and paints based on organic sol¬ vents the amount of solid matter present in the paint should normal¬ ly be less than 40% in order to obtain the desired porosity after evaporation of the solvent. When using paints having a higher content of solid matter, which reduces the energy consumption of the solvent removal operation, it is normally necessary to draw air through the coat of paint before the coat of paint is dried. This may be effected by positioning the mineral fibre sheets on top of a suction box wherein a subatmospheric pressure of 100-1500 N/m 2 is maintained, depending i.a. on the density of the mineral fibre sheets. Alternatively the desired porosity may in these instances be ob¬ tained by treating the mineral fibre sheet surface coated with paint with a spike roller or the like. The air permeable surface layer may also consist of a perforated layer, e.g. a perforated plastic film attached to the surface by means of a binder. One embodiment of the insulating layer according to the invention, which is particularly suitable for external insulation of roofs with a maximum pitch of 5 β and provided with a waterproof membrane, consists of mineral fibre sheets as described above and provided with a dampproof membrane on the internal side of the insulating layer, which dampproof membrane prevents the insulating power of the insulating layer from being reduced by reducing the evaporation of water from the roof surface and the diffusion of water up through the insulating layer. The above air flow resistance may be determined by inserting the object to be measured into a pipe and blowing air through said pipe while the pressure difference and the amount of air blown through the pipe are measured. The invention will now be described with reference to the following example. Example A water-based paint containing a polyvinylacetate binder and dolomite pigment and silicone in a weight ratio of 8 parts by weight of binder, 33 parts by weight of pigment, 3 parts by weight of silicone and 56 parts by weight of water, which composition corre¬ sponds to a content of solid matter of about 40%, was pressed into the surface of mineral fibre sheets having a density of 180 kg/m 3 by means of anti-setoff rollers. The paint was applied in an amount of 3 kg/m 2 and with a penetration depth of 3-4 mm. The sheets were then carried to a kiln with a temperature of 150°C thereby evaporating the water while binder and pigment remained in the outermost 3-4 mm of the mineral fibre sheet. The air flow resistance of the surface layer formed was determined to be 5 N-h/m 3 . The sheets thus produced were positioned without anchoring means and in the form of a coherent insulation layer on a pitched roof.

Claims: C l a i m s 1. An external insulating layer of mineral fibre sheets each comprising a layer of mineral fibres bonded together by a binder, c h a r a c t e r i z e d in that the mineral fibre sheets on the outer side of the insulating layer are provided with a fibre binding surface layer having an air flow resistance of from 0.25 to 8.0 N.h/m 3 . 2. An external insulating layer according to claim 1, c h a r ¬ a c t e r i z e d in that the surface layer is constituted by a coat of paint. 3. An external roof insulating layer according to claims 1 or 2, c h a r a c t e r i z e d in that the mineral fibre sheets on the inner side of the insulating layer is covered by a dampproof mem¬ brane.

Inventors: PETERSEN JOERGEN SKJOLD, PETERSEN, JOERGEN, SKJOLD
Applicants: ROCKWOOL INT, ROCKWOOL INTERNATIONAL A/S
Application year: 1991
Main classification: F16L59
IPC codes: E04B1, E04D13