NO791691L - ROOF CONSTRUCTION. - Google Patents

Abstract

Ceiling.

Description

The present invention relates to a ceiling construction above a heated room in a building. The ceiling construction includes a heat-insulating device that consists of at least two layers of a heat-insulating material, which layers are placed on top of each other, but also

a diffusion barrier and a false ceiling in the form of a cloth.

The thermal insulation layers in known ceiling constructions are usually highly sound absorbent. However, it is common to cover the heat-insulating layers with a false ceiling or a decorative surface layer, partly to

to hide them as they usually do not have an attractive surface, and partly to keep them in place between the rafters. Ceilings with perforated metal fields are also known, which

field contains a heat-insulating layer. Examples of known, decorative surface layers that are used to hide heat-insulating layers are perforated fiber boards and gypsum boards mounted on separate boards, as well as stretched cloth or layer, woven or non-woven, that cellulose or a plastic material. Such false ceiling materials are usually not satisfactory because a large part of the sound produced in the rooms, especially the high frequency sound, is reflected despite the perforations in the materials and cannot be absorbed by the thermal insulation layers which are placed above the false ceiling or the decorative surface layer, It is also

known that high-frequency sound that has passed through a ceiling material is easily reflected by a diffusion barrier, by a plastic material or an impregnated cellulose material that is placed adjacent to the ceiling material and returns through the material in the false ceiling to the room.

The purpose of the present invention is to improve the sound absorption capacity and the acoustic properties of a ceiling construction, which includes a heat-insulating material, a diffusion barrier as well as a false ceiling in the form of a stretched cloth, and to achieve

this by means of simple means and mainly without any additional materials.

It has now been found, quite surprisingly and in accordance with the present invention, that the sound-absorbing capacity of a ceiling construction of the type described above can be improved considerably, provided

a) that the false ceiling, which is a stretched cloth, has such qualities that a significant part of the sound that is produced in

the room, even high-frequency sound, is allowed to pass through the cloth;

b) that at least the heat-insulating layer adjacent to which is made of a soft and porous material, preferably

mineral wool, and has sound-absorbing properties;

c) that the heat-insulating layer adjacent to the cloth is placed between the diffusion barrier and the cloth to also serve

as a sound absorbing material; and

d) that at least a second heat-insulating layer is placed above the diffusion barrier and has such heat-insulating properties that

water condensation under the diffusion barrier is prevented, and also serves as a sound-absorbing material for low-frequency sound, which passes the diffusion barrier.

The sound absorption capacity of the ceiling construction is improved as the high as well as the low frequency sound produced in the room passes through the false ceiling without being strongly reflected. The high-frequency sound is reflected to a fairly large extent by the diffusion barrier above the first heat-insulating layer, compared to the low-frequency sound, but is then weakened and the rest of this, which eventually penetrates the said first heat-insulating layer, passes the false ceiling and enters the room, can hardly be perceived as disturbing .

The basic idea of the present invention is thus,

a), that the acoustic properties of a ceiling construction as described in the introduction to claim 1, if one side is cold (often degrees Celsius) and if the other side is warm, can be significantly improved without using any additional materials, but by using a limited part of the required amount of heat-insulating material as an absorbing material for high-frequency sound, and b) that despite this utilization, it is possible to prevent water from condensing in the sound-absorbing material, which

is a very important result, because water condensation results in a distinctly reduced thermal insulation and also reduced sound absorption.

One has also found, in accordance with the present invention, that if the cloth used as a false ceiling,

has holes with an average side size of at least 0.05 mm, it will also allow high frequency sound (>1000 Hz) to pass easily, the total number of holes preferably covering at least 0' SJ>% of the total area of the cloth. It has thus been shown that it is possible, by trial and error, to regulate the number of holes in the cloth with regard to their average surface area and their total surface area and thereby achieve the result that high as well as low frequency sounds pass through the cloth to a great extent at the same time as the fabric's visual covering ability is satisfactorily maintained, i.e. an ability to cover the first heat insulation layer placed over the fabric and any means for attaching this layer. The main part of the high-frequency sound that passes the cloth is absorbed in the first heat insulation layer and the main part of the remaining sound is absorbed in the same layer after a reflection against the diffusion barrier. The low-frequency sound is also partially absorbed by the first heat insulation layer but is not reflected to a particular extent by the diffusion barrier, but easily passes this and is absorbed to a large extent by the heat insulation material placed on top of the diffusion barrier.

In a preferred embodiment of the present invention, the cloth is a knitted cloth with artificial fibres, e.g. rayon fibers reinforced with nyl fibers and with a fiber diameter of 0.05 to 0.^0 mm and a hole side size of

0.05 - 0.50 mm. The cloth has, before it has been subjected to a treatment, an average hole side size of e.g.

0.18 x 0.18 mm, 0.10 x 0.35 mm and 0.05 x 0.40 mm and are treated with a flame retardant plastic paste, as appropriate

containing an acrylic polymer as well as flame retardant additives and pigments as main ingredients, in such a way that the holes remain essentially open while the holes between the fibers are closed. Such a treatment causes the cloth to have fine pores at the same time as it is made fireproof and elastic, and if it is stretchable, this will not be negatively affected. The small curls on one side of the cloth, by which the cloth is tied, determine the visual coverage and porosity. A porosity as low as 0.3% of the total area and 100 pores per square meter can be achieved. cm<2> of the plastic paste-treated cloth depending on the pressure exerted during the treatment of the cloth with plastic paste, the plastic paste's flow properties, etc. In comparison, it can be mentioned that it is not practical and economical to perforate sheets and plate materials using standard techniques, to a porosity of less than 10$. A typical porosity is 28% with a hole diameter of 1.8 mm and a center distance of 3 mm, i.e. 11 holes per cm 2, or 20% with a hole diameter of

2.5 mm and a center distance of 5 mm, i.e. 4.1 holes per cm 2 It is, however, entirely possible in accordance with the invention to use a perforated sheet of a plastic material or the like as canvas, provided that it is produced in an appropriate manner.

A knitted, stretched fabric made of rayon fibers and prepared in the manner described above allows the passage of high as well as low frequency sounds but completely hides the layers of sound absorbing materials placed above the fabric. Furthermore, the small pores prevent dust from penetrating the cloth and collecting between the cloth and the heat-ice Slar zone.

In another preferred embodiment of the present invention, the fabric which forms the false ceiling is stretched in such a way that an air gap is provided between the fabric and the first heat-insulating and sound-absorbing layer and is thus not affected by any unevenness and joints in the layer. In this way, a valuable additional thermal insulation is achieved due to the small total area of fabric holes and the negligible air convection in the gap due to the holes in the fabric.

Swedish patent application no. 7304368-9 gives examples of false ceilings in the form of stretched cloth or a decorative fabric which can be used in accordance with the present invention. A knitted rayon fabric was used instead of the cotton fabric mentioned in Example 2. It was coated on one side with a paste diluted with water and having approximately the same composition as the paste described in Example 2 and was dried, whereby the fabric was made fireproof. Fabrics produced in this way were tested in a ceiling construction according to the present invention, but it was found (see diagram, plot curve 1) that the porosity and holes in the fabric had been so greatly reduced due to the paste coating that an effect that works in accordance with the invention , could not be achieved. The sound absorption was not at all satisfactory. The results were largely the same as if a tissue without any porosity and holes had been used (see plot curve 2], However, the rayon tissue treatment was modified to the extent that the paste was further diluted when it was used and/or that increased coating pressures were used. It was found, quite surprisingly, that a certain relatively large resolution and/or a relatively high coating pressure made it possible to achieve essentially the same sound absorption (see plotting 3) as when one tissue without any paste coating in it -.-.at all was used ( plotting 4) or when no tissue was used at all (plotting'5) and still at the same time achieving satisfactory visual coverage, which was not the case when a tissue without any paste coating was used at all (plotting 4 ). Rayon fabrics with a sound absorption capability in accordance with the present invention (plotting 3) were examined under a microscope. The thin paste coating had given the fabric a distinct open structure. Each fiber was fully ? covered with paste, but some complete superstructure of the square or rectangular tissue holes could only be observed in a few cases. However, the oblong holes between fibers that were close to each other and that had the same direction had been sealed. Nevertheless, a satisfactory visual coverage of the tissues had been achieved. Mineral wool sheets, their joints and metal wires holding the sheets to a safety net could not be visually detected through the tissue.

The second heat-insulating layer is compliant

with another embodiment of the present invention, divided into fillings placed between the rafters in the ceiling construction and possibly also and above the rafters, while the first heat-insulating and sound-absorbing layer adjacent to the false ceiling mainly covers the fillings as well as the underside of the rafters.

The diffusion barrier is in accordance with another preferred embodiment of the present invention,

a thin and flexible vapor-tight sheet, preferably a sheet made of LD polyethylene with a thickness of less than 0.25 mm. It can be thinner if it is made of HD polyethylene, as this material has very good strength. Such a choice of material and thickness results in vibrations in the diffusion barrier when it is exposed to sound waves that reach it through the first heat-insulating and sound-absorbing layer. Sound energy can thus be absorbed in the ceiling construction in this way. However, it is desirable that the second heat-insulating layer placed above the diffusion barrier is also a porous sound-absorbing material, preferably mineral wool. A polyethylene sheet with a thickness of 0.1 mm allows sound with a frequency of up to approx. 690 Hz, pass easily, a polyethylene sheet with a thickness of 0.2 mm up to approx. 3^5 Hz.

In another preferred embodiment of the invention, the first as well as the second heat-insulating and sound-absorbing layer is supported by a net. This net is held in place by the ceiling beams and they are preferably stretched out. below these and attached to their undersides.

The diffusion barrier and the other heat insulating

and sound-absorbing layer is supported by the net and placed on top of this, while the first and heat-insulating sound-absorbing layer is suspended in the net.

According to another embodiment of the network is

the first heat-insulating and sound-absorbing layer suspended in the web by means of a plurality of threaded suspension fasteners pushed through the layer. These mounts are equipped

with bearing surfaces that are in contact with the underside of the layer and their upper end portions are attached to the net. The bearing surfaces are provided by bending the lower end parts avo the suspension mounts or are heads, appropriately ring-shaped, attached to the suspension mounts.

The present invention also relates to devices which are used to produce the new ceiling construction in the event that they also comprise a net of metal wire in which a heat-insulating and sound-absorbing layer is suspended. This device is characterized by the fact that the net, in addition to the two groups of metal wires that cross each other transversely and which together form a largely regular structure with mesh hole sizes of less than 100 mm, is also equipped with a few metal wire elements placed at roughly equal distances across the net surface. These elements are attached to the rest of the net in such a way that parts of them, possibly produced by cutting the elements at certain points, can be bent outwards from the net surface and thereby form protrusions that are used as suspension devices. The flexible metal wire elements can, according to a special embodiment of the suspension net, be selected metal wires of the net, i.e. the ordinary two groups of metal wires which make up the net itself and which cross each other transversely.

It is also possible to attach the first heat-insulating and sound-absorbing layer to the net by means of strings or the like which are sewn to the net or by means of various hook devices which are pushed through the layer from the underside.

The present invention will be described in more detail in the following with reference to the drawing, where

fig. 1 is a vertical cross-section of a ceiling construction according to the invention,

fig. 2 is a perspective view of a ceiling construction according to the invention and which shows two different embodiments of metal wires designed for hanging mineral wool sheets in a safety net, and

fig. 3 and 4 show preferred embodiments

of a safety net according to the invention.

In the drawing's fig. 1 shows a ceiling construction with two rafters 1 under which a polyethylene sheet and a safety net are attached. Two layers of mineral wool plates 7 are placed between the rafters. The safety net consists of rigid metal wires 2,2 welded to each other. short,

rigid metal wires 3 are attached to the safety net 2 and are directed downwards. The mineral wool plates 5 have been pushed upwards against the safety net 2 whereby the metal wires 3 have penetrated the plates 5. The metal wires 3 have been bent or organs,

e.g. wire rings (not shown in detail) have been attached to the metal wires to hold the plates 5 in place. After the plates 5 have been fixed under the safety net 2, a cloth or fabric 6 is stretched and fixed under the plates. In accordance with the present invention, the cloth 6 allows sound waves to pass easily through it and yet its coverage is so great that it is almost impossible to see the mineral wool plates 5, the joints between the plates and the metal wires 3 through the cloth with the eyes.

Fig. 2 shows a safety net 2 according to the present invention made of metal wires 2,2

welded to'.each other. It is attached to the rafters 1 (only one is shown) with clamps 8. Short, stiff metal wires 3 pointing downwards are attached to the welding points. Two mineral wool plates 5a,5b (drawn with dots as if they were transparent for clarity) are pushed upwards against the safety net 2

and is thereby penetrated by the downwardly directed metal wires 3. Metal wire rings 9 are to hold the plates 5 in place, fixed firmly to the lower parts of the metal wires 3 by appropriate means (not shown). The mineral wool plate 5b is held in place by means of rigid downward facing metal wires 3 which are somewhat longer than the thickness of the mineral wool plates, and therefore the lower parts of these metal wires 3 can, after penetrating the plate, be bent so that they point in a horizontal direction (dotted lines 10) thereby holding the plates in place without additional means. This results in a simpler construction, less work when the mineral wool boards are to be installed, and lower costs.

Fig. 3 shows an embodiment of a safety net according to the invention, which is produced by welding metal wires 2a, 2b to each other, thereby forming rectangular

openings between the threads. In this embodiment, additional metal wires (ll-black) are welded to the ordinary wires (in 2a, 2b - white) in the shown positions next to every third or, depending on the mutual metal wire distance and the thickness of the mineral wool plate, every fourth etc. ordinary thread (2a-white),

in any of the two thread directions of the web. When the mineral wool plates (not shown) are to be fixed under the safety net, the threads 11 are cut in appropriate places with pliers or the like. Cut ends are bent downwards from their nearest welding points, the mineral wool plates are pushed upwards and the portions of the cut, downwardly bent wires which, after complete penetration, are exposed below the lower surface of the plates, are bent upwards to a horizontal position in order to to hold the plates in place.

It is also possible to do without attaching additional threads 11 to the net by welding and instead cut and bend ordinary threads 2a or 2b of the net and use these threads to hold the mineral wool plates against the net. Such a network design is shown in fig. 4 where a thread 2a is cut where it crosses a thread 2b. The next wire 2b that said wire 2a crosses is cut in two places to free said wire 2a from it. Where the third thread 2b crosses said thread 2a, the cut thread 2a is bent downwards. A mineral wool plate (not shown) is pushed upward and the portion of the downward cut wire 2a which, after complete penetration, has been pushed out through the lower surface of the plate is bent upward to a horizontal position to be able to hold the plate in place. Similarly, a suitable number of threads 2a or 2b are cut free and bent and used to hold the mineral wool sheets in place (not shown).

Claims (11)

1. Ceiling construction above a heated room in a building and comprising a heat-insulating and sound-insulating layer (5) as well as a false ceiling (6) consisting of a stretched fabric which enables the passage of a considerable amount of the sound produced in the room through the fabric and into the heat-insulating and sound-absorbing layer, characterized in that the cloth (6) has holes with an average side size of at least 0.05 mm, which holes preferably have a total area of at least 0.3% of the cloth's total area, which cloth (6) visually covers said heat-insulating and sound-absorbing layer (5). 2. Ceiling construction according to claim 1, characterized in that the cloth (6) is a weave of artificial fibers with a fiber thickness of 0.05 - 0.40 mm and a mesh size of 0.05 - 0.50 mm, which weave is treated with a flame-retardant coating in such a way that the meshes are left open with a somewhat reduced size. 3. Ceiling construction according to claims 1 and 2, characterized in that the fabric (6) is stretched with a distance between the fabric and the heat-insulating and sound-absorbing layer (5) placed above. 4. Ceiling construction according to claim 1,2 or 3, also comprising a diffusion barrier, characterized in that the heat-insulating and sound-insulating layer (5), in the horizontal direction, is divided into at least two layers (5,7), which diffusion barrier (4) is placed between the two layers (5 > 7) and the upper of the two layers (7) has such a thickness that water condensation under said diffusion barrier (4) is prevented, and at the same time serves as a sound-absorbing device, especially for low-frequency sounds that quite easily pass the aforementioned diffusion barrier (4). 5. Ceiling construction according to claim 4, characterized in that the upper heat-insulating and sound-absorbing layer (7). is divided into fillings (6) placed between and possibly also above the rafters (1) in the ceiling construction, while the lower heat-insulating and sound-absorbing layer (5) mainly covers the undersides of the rafters (1) as well as said fillings (7). 6. Ceiling construction according to claim 4 or 5" characterized in that the diffusion barrier (4) is such a thin and flexible waterproof sheet, preferably a polyethylene sheet with a thickness of no more than 0.25 mm, that the diffusion barrier (4) itself vibrates when it becomes exposed to sound waves that reach it through the lower heat-insulating and sound-absorbing layer (5). 7. Ceiling construction according to any one of claims 4-6, characterized in that the lower (5) as well as the upper (7) heat-insulating and sound-absorbing layer is held in place by a net (2) which is again held in place by of the rafters (1) and which is preferably pulled under the rafters and attached to the underside of these. 8. Ceiling construction according to claims 6 and 7, characterized in that the diffusion barrier (4) and said upper heat-insulating and sound-absorbing layer (7) are supported by the net (2), while said lower layer (5) is suspended in the underside of the net. 9. Ceiling construction according to claim 8, characterized in that the lower heat-insulating and sound-absorbing layer (5) is suspended in the underside of the net (2) by means of a plurality of wire-like suspension fasteners (3)" which are pushed through the layer (5) and on the underside of this forms bearing surfaces and whose upper parts are attached to the net (2), which bearing surfaces are formed by bending the lower end parts (10) of the suspension fasteners (3), or which are heads (9) which are attached to the suspension fasteners, f, e.g. annular. 10. Device for producing the ceiling construction according to claim 9" comprising a metal wire net, characterized in that the net except for two groups of metal wires (2a, 2b) which cross each other transversely and form an at least mainly regular mesh hole structure with a hole width of less than 100 mm, comprises a plurality of metal wire elements (11) essentially equally distributed over the net surface and attached to the net (2) itself in such a way that parts of them, possibly obtained by cutting metal wire elements (11) at selected points, can be bent out from the plane of the web itself to form protrusions suitable as suspension mounts for the layers. 11. Device according to claim 10, characterized in that the bendable wires (11) are metal wires selected from one or both groups of metal wires (2a, 2b), which cross each other transversely and form the actual net (2).