A roof, a component for a roof, and a method for the installation of a roof Field of the Invention The present invention relates to the construction of buildings and housings. The invention more particularly relates to structures which form part of buildings or houses and to components used herein. The invention still more particularly relates to components adapted for establishing barriers against the transverse passage of heat, of liquids, and of air and vapour. Still more particularly the invention relates to methods of assembling and installing roofing systems and components herefore.

The invention has particular relevance to roofs of a design comprising a bank of mutually parallel rafters wherein the spaces between the rafters are put to use in accomodating insulation material. As compared to designs where the insulation material is installed in other places, this particular design will leave more space available for the dwelling or for other purposes. This advantage in the more effective utilization of the space inside the roof structure will, however, be balanced by the complication of requiring a more delicate installation procedure.

Background In the process of erecting a building it is a major consideration to have a shielding against water and wind in place in an early stage in view of the potential deleterious or degrading influences on many building components by the weather.

Thus according to one construction procedure the lines of rafters are installed and subsequently a flexible roof

sheeting is placed on top of rafters. The sheeting, which comprises a light-weight, water proof foil, provides a shelter or weather membrane with sufficient durability for leaving ample time for other finishing operations, among which the installation of a more durable roof cover on top of and of insulation material, etc below the sheeting.

According to this procedure the insulation material, however, has to be installed from the inside which complicates the operation, in particular in case of a sloping roof. Complications comprise the need for establishment of temporary support of the insulation and downfall of dust from the insulation, which dust may give rise to health concerns. With the insulation in place and properly supported, the vapour impervious membrane has to be installed from the inside, e. g. by nailing it to the interior faces of the rafters whereafter an inside roof lining can be installed. As the vapour impervious membrane is a light foil it is highly suscepticle to being damaged during many parts of the procedure.

In case concealed utility lines, e. g. electrical cables, are to be installed, installation procedures are quite likely to involve perforating the vapour membrane, e. g. to place the cables on the exterior side of the membrane or due to procedures for fastening various utilities.

Installation of the flexible roof, the insulation material and the vapour membrane in the opposite sequence is not a feasible solution as it would involve structural components, the roof lining, the vapour membrane, and the insulation material being exposed to rain for a too long period. Exposure of the insulation material to rain is a particular concern due to the capacity of the insulation

material to hold substantial quantities of water, making drying out a prolonged process.

As some leakages in the vapour membrane must be foreseen in view of many reasons, precautions must be taken in the design phase for the fact that some inflow of moisture into the insulation material is bound to occur during the service life of the building, mainly due to warm air from the accommodation rising and passing through leaks in the vapour membrane into the insulation material where the air (in cold climate) is cooled with the likely result of precipitating water. Therefore the design must allow for ventilating the insulation material in the volume below the flexible roof sheeting. This requires an open space between the exterior face of the insulation material and the interior face of the roof sheeting, and the provision of vents from this space and to the outside. However this solution may not be accomplished e. g. due to the open space being choked by a sagging flexible roof sheeting, accidental piling of insulation material, etc. Another disadvantage is the occupation of space which is not available for other purposes.

In view of these circumstances the installation of this kind of roof still involves a complicated and costly process, and problems with moisture inside the roof construction may also easily occur.

German published application 24 12 830 provides an insulation panel which comprises a plate, insulation material, a vapour impervious membrane, and a hose enclosing the other components. The plate is supported by its margins onto the rafters. The plate by means of the hose supports the insulation material and the vapour membrane.

The incorporation into an insulation panel of a structural plate contributes heavily to the cost of materials and complicates handling, transportation, and adaptation to site requirements to the extent that this solution is hardly commercially viable. Furthermore the structural plate and the part of the hose at the exterior side create obstacles to the ventilation of the insulation to the exterior side, generally required.

Summary of the Invention The invention in a first aspect provides a method as recited in claim 1. This method provides a swift and simple procedure for bringing in place structural support for subsequent installation of insulation material. Any downfall of dust from the insulation material is safely contained by the vapour impervious sheet below the insulation material. Adverse weather conditions during the operation of securing the sheets is not a major problem as the sheet provides immediate protection against the rain and as the sheet will not absorb and retain any substantial quantity of water.

Once the sheets are installed the insulation material may be put in place with great speed as the insulation material, e. g. mats, merely has to be deposited onto the sheets. Thereafter a suitable kind of roofing, e. g. a flexibel roof sheet, may be put into place so as to cover the insulation material.

The invention in a second aspect provides a method as recited in claim 2. This method provides a roof structure with the advantages in handling and installation as outlined above.

The invention in a third aspect provides a double sheet as recited in claim 4. This double sheet comprises a

first and a second web arranged in overlying relationship and joined along one respective edge, while not adhered over the remaining area. The product may be provided in continuous lengths or in rolls or it may be cut to suitable lengths ready for installation as appropriate.

The joining along one edge ensures that both layers are available on site in a convenient fashion. The semi- finished character of the product facilitates adaptation to site requirements, e. g. to accommodate obstructions and varying spacings between the rafters.

According to a preferred embodiment the roof sheet foil and the vapour membrane foil should be matched in order that air permeability across the roof sheet foil is at least five times and preferably ten times the air permeability across the vapour membrane. If this condition is met, there will be no need to provide for additional venting of the insulation material. One foil combination, which satifies this criterion, is a pair of polyethylene foils, among which the thickness of the roof sheet foil is equal to one tenth the thickness of the vapour membrane foil. Other foil combinations could comprise a roof sheet of polyurethane, polyamide, or another permeable foil.

Dispensing with vents across the roof sheet entails a particular advantage as the roof sheet, although slightly permeable to air, is capable of sustaining a moderate air pressure differential, hereby relieving the vapour membrane of a corresponding partial pressure differen- tial. Hereby the roof sheet contributes favourably towards the purpose of stemming any convection of air from the accommodation and into the insulation material.

According to a preferred embodiment the webs may be joined along opposite edges so as to provide a hose. In

this case insulation material will have to be inserted from the end of the hose or through cut slits.

The invention in a further aspect provides an insulation element as recited in claim 7. This provides a prefabricated element which lends itself to effective manufacturing and which provides the insulation material in a virtually moisture proof envelope (except possibly for openings at the ends). Providing the insulation material in an envelope is a major advantage as it permits transportation and stocking of the elements in the open air with no risk of the insulation material becoming soaked with water prior to installation. The insulation elements easily conform to site circumstances such as obstructions, variations in the rafter interspacing, etc.

The invention in a still further aspect provides a roof as recited in claim 8. This roof permits the advantageous installation procedures as explained above.

According to a preferred embodiment this roof comprises an insulation liner, i. e. an additional layer of insulation material installed at the interior side of the vapour membrane. This retracts the vapour membrane from the roof lining towards the accommodation, thus minimizing the risk of accidental perforation of the membrane, e. g. by various istallation operations carried out from the accommodation side. The insulation liner also provides a space available for the drawing of utility lines, e. g. electrical cables, so that they may be installed concealed as seen from the accommodation side but without perforating the vapour membrane.

According to a preferred embodiment the depth of the insulation liner is less than or equal to half of the

depth of the insulation material arranged exterior to the vapour impervious sheet. This ensures that the temperature differential from the accommodation and to the vapour membrane does not become so large that there would be any risk of precipitating moisture inside the insulation liner.

The invention will appear in further detail from the following description of preferred embodiments given with reference to the drawings in which Fig. 1 illustrates part of a roof according to the invention, the view showing a section perpendicular to the axes of the rafters, Fig. 2 illustrates a view similar to Fig. 1 but showing an earlier stage of the installation by which stage the double sheet has been partially installed, Fig. 3 illustrates a cross section in a double sheet according to the invention, and Fig. 4 illustrates a cross section in an insulation element according to the invention.

Description of the preferred embodiments All figures are schematic and simplified so that only details considered important to enable those skilled in the art to carry out the invention have been shown, whereas other details have been omitted for reasons of clarity. All figures use the same references for identical or corresponding items.

Reference is first made to Fig. 1 which illustrates a section through part of a roof 1. The roof structure comprises rafters 2. The rafters 2 comprise solid beams arranged in juxtaposition in a spaced, mutually parallel relationship along a common plane so as to define generally a plane, sloping from the ridge of the roof to the base of the roof (not shown).

The rafters comprise exterior faces 5, i. e. the surfaces facing outwardly or away from the accommodation, and interior faces 13, i. e. the surfaces facing downwardly or towards the accommodation. The rafters further comprise lateral faces 17.

This type of roof structure may be used in a variety of inclination angles. Generally this type of roof structure is particularly adapted for an inclination angle within the range from 12° to 45° from the horizontal.

In the roof in Fig. 1 the space intermediate the rafters is utilized for the placing of insulation, the insulation comprising a layer of insulation material 3 and an insulation liner 4. The flexible roof sheet 6 is placed on top of the rafter exterior faces 5. The roof sheet is secured to the rafter exterior faces by nails 7. Thus the roof sheet spans the gap intermediate a pair of adjacent rafters.

Along the rafter exterior faces and on top of the roof sheet lists 8 are secured and on top of the lists battens 9 extending perpendicularly to the lists have been secured.

The battens support the roof covering 10 which comprises e. g. roof tiles, roof plates or some other type of weather-resistant, durable roof elements. The lists 8

serve the purpose of spacing the battens from the roof sheet in order that any water flowing downwardly on top of the roof sheet may pass underneath the battens.

The roof sheeting generally comprises a thin foil material which is largely impenetrable to water. Various foils may be used. A polyethylene foil of a thickness of 0.015 mm has been found to perform well. Foils which combine impermeability to water with a permeability to air are favoured because they permit drying out the insulation material to the exterior side. Suitable air- permeable foils comprise polyurethane foils and polyamide foils. The foil may comprise a surface finish adapted for mechanical protection and for protection against degrading ultra violet radiation.

The roof further comprises a vapour membrane essentially composed of sections of a vapour impervious sheet 11.

According to the invention the vapour impervious sheet sections 11 are placed in contact with the rafter exterior faces in order that the sheet may extend along parts of the rafter lateral faces and along the interior side of the insulation material 3.

The vapour impervious membrane serves the purpose of blocking passage of air and moisture from the accommodation and into the insulation. Various materials may be used. A polyethylene plastic film of a thickness of 0.150 mm has been found to perform well. A film reinforced with glass fibers on polyester fibers provides excellent structural performance.

In the roof illustrated in Fig. 1 the insulation comprises an additional layer referred to as the insulation liner 4 which has been placed at the interior side of the vapour impervious sheet 11. The roof further

comprises a roof lining 12 secured in contact with the rafter interior faces and providing an agreeable finish towards the accommodation. The insulation liner spaces the vapour sheet from the roof lining 12. This retracts the vapour impervious sheet from the zone close to the roof lining where it would be exposed to damage, e. g. by operations to secure utility installations involving drilling, screwing or nailing in the roof lining. The space between the vapour impervious sheet and the roof lining is also available for placing utility lines, e. g. electrical cables, concealed from the accommodation but without having to make them cross the vapour impervious sheet.

Reference is now made to Figs. 2 and 3 for a description of a double sheet according to the invention and for a description of the installation operation.

The double membrane 14 comprises two foil webs joined along one respective edge by a seam or a weld 15. The foil webs are generally placed overlaying relationship, however, they have different widths. The upper foil web, referring to Fig. 3, adapted for providing the roof sheet is adapted to span the gap between the exterior faces of a pair of adjacent rafters in a generally taut fashion with ample width for securing the margins to the rafter exterior faces.

The lower foil web, as illustrated in Fig. 3, adapted for providing the vapour impervious sheet 11 is wider than the upper foil web. This permits the lower foil web to span the interspace between a pair of adjacent rafters in a sagging fashion.

In a roof with rafters of a height of 20 cm arranged in a line with 90 cm spacing, the width of the upper foil web

could be e. g. 100 cm, while the width of the lower web could be approx. 130 cm. Adaptation of the particular dimensions to a particular site condition will be within the capabilities of those skilled in the art.

In order to install the roof the double membrane is placed as illustrated in Fig. 2, the joined edge being nailed to the exterior face of one rafter and the opposite edge of the wider foil web which is to form the vapour impervious sheet 11 being nailed to the exterior face of the adjacent rafter. This foil web has a width permitting it to span the rafter interspace in a sagging fashion. The upper foil web is flipped over to the side as shown in Fig. 2.

Subsequently mats of insulation material sized generally to match the rafter interspace are placed on top of the vapour impervious sheet 11, this sheet providing structural support for the mats of insulation. Once the mats of insulation have been brought in place, the upper foil web adapted for providing the roof sheet 6 is flipped back on top of the insulation and secured along the respective edge to the appropriate rafter exterior face. By this stage the mat of insulation and the roof sheet have been brought in place and the roof sheet fulfills the purpose of protecting the insulation material against weather conditions.

Reference is now made to Fig. 4 which shows a section through an insulation element according to the invention.

The insulation element 16 comprises an upper foil web for providing the roof sheet 6, a mat of insulation 3 and a lower foil web for providing the vapour impervious sheet 11. The foil webs are joined along respective opposite edges by seams 15 so as to form a hose with the seams providing laterally extending flanges.

This product may be provided in continuous lengths, in rolls or in cut lengths as appropriate. In other embodiments the product could be provided in lengths where the ends of the hose would be closed so as provide a closed envelope.

In the roof according to the invention the insulation material is sealed and protected almost hermetically and the risk of accidental perforation of the vapour membrane is minimized, thus virtually eliminating the need for providing for venting of the space accommodating the insulation material. This obviates the need for providing extra space in the roof for venting the insulation material. This saving in space requirement may be put to advantage in various ways or combinations of ways. One way could be to put in more insulation material in the roof, another way could be to provide more space for the accommodation quarters, etc.

Although specific embodiments of the invention have been described above, this description is intended for the sole purpose of exemplifying how the invention may be carried out but not with the purpose of restricting the scope of the invention which may be varied or implemented in numerous other ways within the ambit defined by the appended patent claims.