FIELD OF THE INVENTION

[0001] The present invention relates to building membranes for use in building elements comprising walls, floors, ceilings and roofs of domestic and commercial buildings. Such membranes are provided for various purposes, including providing a barrier to prevent ingress of water; a barrier to prevent the loss of conditioned air and a radiant barrier to provide thermal insulation. Building membranes may assist, or impede, as required, the appropriate level of moisture transfer through building elements.

BACKGROUND OF THE INVENTION

[0002] The following discussion of the background to the invention is intended to facilitate an understanding of the invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge as at the priority date of the application.

[0003] Excessive levels of moisture inside of a building can promote condensation on surfaces in the building and lead to mould forming on those surfaces. This can affect the health of residents of affected buildings and can result in damage to building surfaces and even to the structure of the building.

[0004] The issue of moisture within buildings and the effect on the building has become more pronounced in recent years. As recently as twenty or thirty years ago, most houses in Australia were unheated, except for small gas or electric space heaters and those houses were either not cooled, or only cooled in one or two rooms. The houses were also well ventilated and importantly, were in general, uninsulated. Houses typically had vents installed in every room to ensure the dispersal of fumes from unflued gas heaters (and earlier from gas lighting) and even when vents were not installed, the absence of caulking around window and door frames ensured a very high rate of ventilation by draught. As a result, water vapour created by internal activities was usually quickly vented to the outside, so that inside damage did not occur. [0005] Where mould did form on walls, it tended to disappear over the summer months. Because the walls were generally uninsulated and often leaky, even if there was significant amount of moisture accumulated in the materials of the wall in cool winter weather, it would quickly dry out in the warmer weather of spring and summer, or during a warm, sunny afternoon following a cold night.

[0006] Now however, houses are commonly heated in the winter and cooled in the summer, and newer or renovated houses are better sealed and insulated than before. These houses are however, often poorly ventilated, so as to effectively prevent excess moisture within the house from escaping. Because walls of new and renovated houses are now insulated as a standard procedure, the steady state dew point on cold nights is located within the cavity of the walls where the insulation is located. Temperatures within the insulation are relatively more stable than in the cavities of an uninsulated house, so condensed moisture takes longer to re- evaporate. Thus the moisture can accumulate as water and cause mould and other damage to the structure within the cavity.

[0007] The generation of mould within a building can have an effect on resident health, while major structural problems include degradation of plasterboard, dry rot in timber and, in extreme situations, corrosion of fasteners and other steel components. In addition, these problems can occur well before water vapour levels in a wall cavity reach the point where condensation is observed. In relation to mould, different moulds thrive under different conditions. The critical issue is the duration of the specific conditions which favour a particular species of mould. In traditional houses of the kind discussed above, conditions would change from season to season and over the course of each day. This would limit the timeframe during which different types of moulds could thrive, often to the point that mould would not have sufficient time to generate to a problem level.

[0008] A modern air conditioned building, however, can provide steady-state conditions which can be a perfect incubator for one or a small number of particular species of mould. This is particularly a problem in the wet and humid tropics. Thus, the mould remains alive rather than perishing as it would in an older house. The key measure needed to reduce the growth of mould is to maintain the relative humidity below 80%. [0009] The present invention is principally concerned with ensuring the passage of water vapour through the walls of a building, either from the inside out or the outside in, while air movement and the infiltration of liquid water is prevented and a low emittance face for added R-Value to a space or area of the building is provided. The invention has application in walls, floors, ceilings and roofs. The invention has been developed with the following principles in mind.

[0010] Water vapour can travel through the cavity of a building element (a wall, floor, ceiling or roof for example) through air movement, dispersion through still air gaps, or dispersion through building materials.

[001 1] Air movement

[0012] In most buildings, the principal mode of water vapour transport through the cavity of a building element is by air movement. Warm damp air moving through the internal lining of the building element and circulating within the insulation in the cavity of the building element will be cooled as it approaches the external side of the building element. When the air cools to the point that it becomes saturated - i.e. at the dew point - the vapour will condense into liquid water. Air movement provides capacity to transport water vapour, into and out of cavity walls and roof spaces; thus it is important to employ air barriers, as well as caulking, to control the flow of air though building cavities.

[0013] Dispersion through still air gaps

[0014] Large amounts of water vapour can readily disperse through small gaps in a wall structure and through porous materials. This vapour dispersion is often not due not to air movement but to the equalisation of partial vapour pressure in different sections of the cavity of a building element. Vapour pressure can be rapidly equalised without significant air movement though relatively small holes.

[0015] Dispersion through building materials

[0016] Moisture can also move through porous materials under vapour pressure. Water vapour transmission varies with vapour pressure, and therefore with air temperature and relative humidity. [0017] Buildings that are constructed with masonry, timber and plasterboard materials have a significant hygric capacity. That is, these materials can absorb and release water vapour over a normal cycle of changes of wet and dry weather conditions. In the average Australian brick veneer (timber framed and brick clad) home (186 m2) approximately 1800 to 2300 kg of wood is located in the exterior walls. This yields a hygric capacity of approximately 180 to 230 kg of water or 170 to 190 L of water via hygric redistribution.

[0018] Australian brick veneer houses with timber frames have 46% less timber content than equivalent houses in the USA. This is due to the extensive use of plywood or other timber fibreboard sheathing on the exterior of timber framing for bracing in USA. Accordingly, the hygric capacity of homes in the USA is much greater than that in Australia.

[0019] Contrary to common belief, in Australia (though not necessarily in other countries which have more severe climates), the principal moisture problem encountered in houses and other buildings in most regions of the country during cold and/or rainy winter weather is not water penetration into the house or building from outside, but rather, vapour from inside the house or building condensing in walls and roof spaces as it attempts to travel to the outside of the house or building. The opposite direction of vapour travel can occur in summer, with damp external air condensing in the wall and ceiling cavity insulation of air-conditioned buildings, particularly in the wet tropics and sub-tropics. Figures 1 and 2 illustrate the direction of vapour travel through a wall based on the difference in water vapour pressure between the inside of a house and the outside in both winter and summer conditions.

[0020] In general, vapour moves from the warm side of a wall to towards the cold side. This means that in most of Australia, the direction of vapour drive varies through the seasons from outwards in winter to inwards in summer. It can vary greatly between houses in the same suburb or area due to differences in microclimate, in air conditioning, heating and sealing of the house, and in occupant behaviour. The direction of vapour drive even varies greatly between different walls of the same house or building, depending on orientation and exposure of the wall.

[0021] In general however, the principal direction of vapour drive in modern houses in temperate regions of Australia is from inside to out, even as far north as South East Queensland, and moisture problems are associated mainly with winter weather. It is therefore important that where the direction of vapour drive is from inside to out, that buildings can "breathe" to allow trapped moisture to escape to the exterior in winter weather. Vapour barriers should therefore not be used where there is a significant seasonal reversal of direction of vapour drive as this would lead to condensation behind the vapour barrier during some parts of the year. Thus, in climates where the direction of heat flow and vapour drive varies from winter to summer, a vapour barrier correctly placed for winter conditions will be incorrectly placed, and trap moisture, in summer; and vice-versa. Accordingly, in these climates, building construction should allow for the flow of moisture in both directions, i.e. from the inside out or from the outside in.

[0022] The movement of vapour within a building is also affected by the ventilation of the building and building designers often have conflicting objectives in

Substitute Sheet

(Rule 26) RO/AU relation to ventilation. For example, designers who focus on energy efficiency strive for minimal ventilation rates to reduce heating and cooling loads, while others, with attention to health issues, recommend much higher levels of ventilation. In relation to health, ventilation partially replaces stale contaminated indoor air with fresher outdoor air to improve indoor air quality. Indoor contaminants include particles and gases, in which particles include dust, dust mites, pollen, mould, animal allergens and pet hair, while gaseous contaminants are principally volatile organic compounds (VOCs), released from adhesives, paints and building materials. These contaminants degrade indoor air quality, aggravating allergies and asthma attacks. Unfortunately, many highly energy-efficient homes experience unintended poor indoor air quality and moisture problems.

[0023] The dominant moisture load from the point of view of moisture risk is that exhaled by occupants as indicated in the table below:

Table 1. Typical sources of indoor water vapour.

Source Water Vapour Generation

Cooking & Dishwashing 2.5 L/day

Laundry & Drying 14 U week

Shower 0.25 L each

Bath 0.05 L each

Floor and Window Wash 1.5 L per 10m2 per wash

Indoor Plants 0.8 L per plant per day

Person - Exercising 5.0 L per person per day

Person - Sedentary 0.6 L in l O hrs

Gas Appliances 55.0 L per 100m3 of gas

[0024] Thus, typical moisture load combined with low ventilation has a significant influence on indoor relative humidity and thereby potential for mould growth.

[0025] Sheeting or "wall wrap" that is used as a water barrier in walls of buildings can be perforated to facilitate vapour movement though the roofs and walls. However, the sheeting that is available to date has generally suffered from the problem that the greater the permeability for vapour passage the less effective the sheeting is as a water barrier.

[0026] The applicant has recognised that improved sheeting would be useful that allowed for vapour travel in each direction through the sheeting, but which retains sufficient water barrier characteristics. An improved sheeting would be one that satisfies the requirements specified in Australia/New Zealand Standard 4200.1 , for a Pliable Building Membrane with "High Water Barrier" and, at the same time, a "Low Vapour Barrier".

SUMMARY OF THE INVENTION

[0027] The present invention provides a building membrane for inclusion in the walls, ceiling, floor or roof of a building, the membrane including a first supporting layer and a waterproof or high water barrier permeable layer, the first supporting layer laer being adhered to the permeable layer, the supporting layer being perforated.

[0028] The present invention provides a vapour permeable building membrane that in some forms can form a combined reflective insulation and water-proof sarking and which, in one manifestation, can provide a thermal break between the cladding of a building and the frame of the building, such as a timber or steel frame.

[0029] The first supporting layer will often be a reflective layer such as a foil layer and such a reflective layer can comprise a laminate of the reflective layer and a substrate such as a polymer film, or a woven polymer, such as woven polypropylene or woven polyethylene. Alternatively, it can just be a foil layer, typically over 30 microns. The first supporting layer can alternatively be of a different form such as an aluminium metallisation layer. Where a substrate is employed, the substrate can alternatively be a flexible foam, such as selected from one or more of expanded and/or extruded polystyrene, polyurethane or polyisocyanurate, or the substrate can be a batting fabric.

[0030] The first supporting layer can have any suitable infra-red emissivity but as a reflective layer, the infra-red emissivity is preferably no more than 0.08 in an antiglare coated product, or no more than 0.03 in non-anti-glare coated products. This allows the desired R-Value to be achieved.

[0031] The building membrane of the present invention can further include a first non-woven fabric layer, in which the first supporting layer is adhered to the fabric layer and the fabric layer is adhered to the permeable layer. While the fabric layer and the waterproof permeable layer have been described as separate layers, the industry or a person skilled in the art would regard them as one laminate. The laminate thus comprises a very thin water-proof permeable layer, which is typically supported by a layer of highly permeable non-woven fabric. A better form of this laminate is that the water-proof permeable layer is sandwiched between two such layers whereby the layers of non-woven fabric on either side protect the waterproof permeable layer from mechanical damage during manufacture as well as during installation on site. In these forms of the invention, the supporting layer is adhered to the permeable laminate.

[0032] The first fabric layer can be a polypropylene, polyethylene, polyester, nylon, polyurethane or rayon fabric. The fabric layer can be a spun-bonded, spun- lace or spun-laid fabric. The first fabric layer can provide the medium by which vapour or moisture, received through the perforations of the reflective layer, travels along the permeable layer to the points of permeance of that layer, so as to travel through the permeable layer.

[0033] The permeable layer can be of any suitable form, such as a polyethylene layer manufactured for vapour permeance. Other polyamides can also be used. A number of other materials also have the vapour permeance property and can be employed. The permeable layer can be a film, or alternatively a melt-blown layer on a substrate such as polypropylene non-woven fabric, or still alternatively, it can be applied as a solution using a roller coater.

[0034] Adhesive is used between the first supporting layer and the first fabric layer and while this can be any suitable adhesive, example adhesives include polyethylene extrudate, pressure sensitive adhesives, and hot melt adhesives.

[0035] A layer of "batting" fabric, or non-woven fabric, or felt textile can be interposed between the first supporting layer and first fabric layer, or between the first supporting layer and the permeable laminate. The batting fabric provides a bulk insulation layer which can create a thermal break where required between the framing members and the external cladding of a building. The batting fabric can be a needle punched non-woven fabric, or other felted material. It can also be a polymer foam, such as an open-cell foam. [0036] A second fabric layer can be adhered to the side of the permeable membrane which is opposite to the first fabric layer and a second reflective layer can be adhered to the second fabric layer. In this arrangement, the second reflective layer can be perforated with the perforations terminating prior to the permeable layer.

[0037] The second fabric layer can be a polypropylene fabric or a polyethylene fabric. Other fabrics or textiles can be employed. Alternatively, polypropylene or polyethylene non-woven fabrics can be employed. In one example, the second fabric layer is a spun-bonded polypropylene non-woven fabric.

[0038] The adhesive between the second fabric layer and the permeable membrane can be of any suitable kind, such as a polyethylene extrudate.

[0039] The second reflective layer can be a foil layer, although like the first supporting layer when formed as a reflective layer, it can be of an alternative material, such as an aluminium metallisation layer.

[0040] A batting fabric, or non-woven fabric, or felt textile, can also be interposed between the second fabric layer and the permeable membrane and the batting fabric can be a needle punched non-woven fabric.

[0041] Anti-glare coatings can be applied to the outer facing surface of the first supporting layer or any supporting or reflective layer.

[0042] The layers described above can comprise the only layers that a building membrane according to the invention need have, keeping in mind the separate layers required for a single supporting layer as compared to a membrane that includes a first supporting layer and a second reflective layer. However, further layers can be provided and such examples will be evident from the drawings that follow later herein.

[0043] The present invention also extends to a method of manufacturing a building membrane of the kinds discussed above, whereby the method in its broadest form includes forming the building membrane other than to perforate the first supporting layer, then perforating the first supporting layer to a depth that the perforations terminate prior to extension through the permeable layer. [0044] Where the building membrane includes a second reflective layer, the invention extends to a method of manufacturing a building membrane of the above described kind with both a first supporting layer and a second reflective layer and once so formed, each of the first and second layers are perforated with the perforations terminating prior to extension through the permeable layer. The first and second layers can be perforated separately or simultaneously from either side of the building membrane.

[0045] In a method according to the invention, the method thus includes adhering a first supporting layer to a first fabric layer, adhering the first fabric layer to a permeable membrane and then perforating the first supporting layer to a depth that the perforations terminate prior to extension through the permeable layer.

[0046] The above method can further include adhering a second reflective layer to a second non-woven fabric layer, adhering the second fabric layer to the side of the permeable layer opposite to the first fabric layer and then perforating the second reflective layer to a depth that the perforations terminate prior to extension through the permeable layer.

[0047] In building membranes and the method of the invention, an advantage that is provided is that by perforating the first supporting layer and the second reflective layer if provided after the components of the building membrane have been assembled and adhered together, the perforations perforate through the adhesive that adheres the supporting layer to the fabric layer and this ensures that the openings in the supporting layer that are formed by perforation remain open. Where the supporting layer is perforated prior to adhesion to the fabric layer, or to the permeable laminate, the adhesive can penetrate into the openings in the supporting layer and block the openings, thereby decreasing the porosity of the reflective layer.

[0048] A building membrane according to the present invention advantageously can have the following characteristics: o Infra-red emissivity no more than 0.05 o High Water Barrier in accordance with AS 4200.1 , o High permeance - not yet defined in an Australian standard, but generally defined as 70.5 grams per square metre or more at standard test conditions in accordance with ASTM E96 (10 Perms) in US literature.

[0049] If the material is intended to provide a thermal break in accordance with the NCC/BCA: o Material R value greater than R0.2 when compressed by 4.8 KPa pressure.

[0050] A building membrane of this kind is expected to have strong demand in the building industry.

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order that the invention may be more fully understood, some embodiments will now be described with reference to the figures in which:

[0052] Figures 1 and 2 illustrate the present invention as applied to a solid wall with a 25mm cavity (Figure 1 ) and a solid wall without a cavity (Figure 2).

[0053] Figure 3 is an exploded view of a building membrane according to one embodiment of the present invention.

[0054] Figure 4 is an exploded view of a building membrane according to another embodiment of the present invention.

[0055] Figure 5 is a cross-sectional view of the building membrane of Figure 3 and illustrating perforating needles.

[0056] Figure 6 is an exploded view of the building membrane of Figure 3 and illustrating perforating needles.

[0057] Figure 7 is a cross-sectional view of the building membrane of Figure 4 and illustrating perforating needles.

[0058] Figure 8 is an exploded view of the building membrane of Figure 4 and illustrating perforating needles. DETAILED DESCRIPTION OF THE DRAWINGS

[0059] With reference to Figure 1 , a cross sectional view of the floor and wall of a building is shown. The view includes a concrete slab 10 and a layered wall construction 1 1 . The wall construction includes an internal wall lining 12, a stud wall 13, a dampcourse/termite barrier 14, a batten 15, a fibre cement sheet 16, a building wrap 17 and a reinforced render 18.

[0060] The same reference numerals in Figure 1 are used in Figure 2 to represent the same features. Thus, the arrangement in Figure 2 includes a slab 10 and wall construction 11 formed of an internal wall lining 12, a termite barrier 14, a cement sheet 16 and a reinforced render 18.

[0061] The difference between the Figures 1 and 2 arrangements and the components illustrated in those arrangements will be readily apparent to a person skilled in the art and no further discussion of those arrangements needs to be made.

[0062] In each of the Figures 1 and 2 arrangements, a building membrane 20 in accordance with the invention is provided. In Figure 1 , the membrane 20 is positioned between the stud wall 13 and the batten 15. In Figure 2, the membrane is positioned on the inside of the cement sheet 16.

[0063] While Figures 1 and 2 show the membrane of the present invention as it is applied to wall constructions, it needs to be appreciated that the invention can also be utilised in different forms of wall constructions, as well as ceilings, roof spaces and floors.

[0064] Figure 3 is an exploded view of a building membrane according to one embodiment of the present invention. The building membrane 25 shown in Figure 3 is constructed of a series of layers comprising a first supporting layer in the form of a reflective layer being an aluminium foil layer 26, an adhesive 27 such as a polyethylene extrudate, a polyester fabric 28, such as a polypropylene non-woven fabric or a polyethylene non-woven fabric, a further adhesive 29, again, such as a polyethylene extrudate, a spun-bonded polypropylene layer 30, a permeable layer being a melt-blown polypropylene layer 31 and a further spun-bonded polypropylene layer 32. The layers form a building membrane of about 500 micron when secured together. The adhesives 27 and 29 can alternatively be aqueous polymer adhesive or polyamide extrudate.

[0065] Perforations extend through each of the layers 26 to 29 but terminate prior to the layer 30. The perforations are shown as a series of dots in the layers 26 to 29. The perforations extend through the adhesive layers 27 and 29.

[0066] The permeable layer 31 is a waterproof or high water barrier permeable layer which is adhered on either side to spun-bonded polypropylene layers. The inside layer 30 forms a fabric layer that, in this example, provides the medium by which vapour or moisture, received through the perforated layers between it and the reflective layer 26, travels along the permeable layer 31 to the points of permeance of that layer, so as to travel through the permeable layer 31 . The outside layer 32 is a protective layer to protect the permeable layer 31 from damage.

[0067] Importantly from a marking perspective, the outwardly facing surfaces of the layers 26 and 32 can be printed if required.

[0068] Figure 4 is a further exploded view of a building membrane 35 according to another embodiment of the present invention. The building membrane 35 shown in Figure 4 is constructed of a series of layers comprising a first reflective layer being an aluminium metallisation layer 36, a polyester fabric 37, such as a polypropylene woven fabric or a polyethylene woven fabric, an adhesive 38, such as a polyethylene extrudate, a spun-bonded polypropylene layer 39, a permeable layer being a melt- blown polypropylene layer 40 and a further spun-bonded polypropylene layer 41 . The layers form a building membrane of about 480 micron when secured together.

[0069] Perforations extend through each of the layers 36 to 38 including the adhesive layer 38, but terminate prior to the layer 39. The perforations are shown as a series of dots in the layers 36 to 38.

[0070] Figure 5 is a cross sectional view of a portion of the membrane 25 with the layers 26 to 32 adhered together. Figure 5 also shows perforating needles 45 in broken outline and in the extreme position or the maximum stroke position. In the position shown, the perforating needles 45 extend through the aluminium foil layer 26, the adhesive layer 27, the polyester fabric layer 28, and the further adhesive layer 29. The perforating needles 45 further extend into the spun-bonded polypropylene layer 30, but not through that layer. Rather, the perforating needles 45 terminate within the layer 30 so that they do not perforate into the highly permeable melt-blown polypropylene layer 40 or beyond.

[0071] Figure 6 illustrates the Figure 5 arrangement but in perspective view.

[0072] Figure 7 is a cross sectional view of a portion of the membrane 35 with the layers 36 to 41 adhered together. Figure 7 also shows perforating needles 46 in broken outline and in the extreme position or the maximum stroke position. In the position shown, the perforating needles 46 extend through the aluminium metallised layer 36, the polyester fabric layer 37, and the adhesive layer 38. The perforating needles 46 further extend into the spun-bonded polypropylene layer 39, but not through that layer. Rather, the perforating needles 46 terminate within the layer 39 so that they do not perforate into the highly permeable melt-blown polypropylene layer 41 or beyond.

[0073] It is to be noted that the membranes 25 and 35 have a single reflective layer only, but it is to be appreciated that a second reflective layer could be applied to those membranes if preferred, by applying a polyester fabric layer to the spun- bonded polypropylene layers 32 and 41 and laminating a further reflective layer to the polyester fabric layers.

[0074] Moreover, a batting layer could be applied to the membranes 25 and 35 by interposing a batting layer between the polyester fabric layer 28 and the spun- bonded polypropylene layer 30 of the membrane layer 25, or between the aluminium metallised layer 36 and spun-bonded polypropylene layer 39.

[0075] The perforating needles 45 and 46 can be a chisel or cone shaped pin up to 2mm in diameter. Approximately 6,000 perforations/square metre can be made by either cold or hot pin perforation techniques. Experiments suggest that with this type of perforation, increasing the number of perforations beyond this density provides further improvements in permeance.

[0076] The invention described herein is susceptible to variations, modifications and/or additions other than those specifically described and it is to be understood that the invention includes all such variations, modifications and/or additions which fall within the spirit and scope of the present disclosure.

[0077] Throughout the description and claims of this specification the word "comprise" and variations of that word, such as "comprises" and "comprising", are not intended to exclude other additives, components, integers or steps.

[0078] Future patent applications may be filed in Australia or overseas on the basis of or claiming priority from the present application. It is to be understood that the following provisional claims are provided by way of example only, and are not intended to limit the scope of what may be claimed in any such future applications. Features may be added to or omitted from the provisional claims at a later date so as to further define or re-define the invention or inventions.