Field of the Invention

The present invention relates to water vapour permeable tapes and methods for controlling air and water vapour movement in building constructions such as wall constructions, roof constructions, floor constructions, and ducting (such as heating, ventilation and air conditioning ducting).

Background to the Invention

With the ever increasing desire for thermal efficiency building structures often make use of wall, roof or floor constructions that include various types of specialised insulation layers to provide thermal insulation. Older buildings are refurbished with additional layers of insulation being provided. At the same time control of air movement and moisture is required.

Typical examples include the use of insulation boards of a foam material, often including reflective facings, such as aluminium foil facings. Such boards can be used, for example: to externally insulate an existing wall, before application of a new outer surface; to provide additional insulation within the cavity of a cavity wall structure; and in rainscreen cladding structures.

When building a structure moisture may be left within cavities or between layers of e.g. a wall structure in locations that can cause damage to materials from corrosion or mould growth. When construction is completed the design intention is to provide an acceptable degree of comfort within the building whilst obtaining high energy efficiency.

During use of the building moisture in vapour form will tend to move throughout the building and into and through its fabric of construction. The direction of movement depends on vapour pressure differentials, generally these are temperature dependent. For example water vapour will tend to move from inside a building to the outside in northern climates where the inside is normally warmer. For southern climates the opposite, from outside to inside the building may occur as the inside of the building may be cooler than outside. The moisture can be naturally occurring in the air outside or generated indoors from heating, showers, breathing or cooking. This moisture can cause condensation problems as vapour moving from a warm area is suddenly cooled, and does not have a ready escape route.

At the same time repair or replacement of component parts of the structure, damaged due to lack of moisture control, is to be avoided.

Similar considerations apply when considering heating, ventilation and air conditioning systems. For energy efficiency reasons the ducting employed to transport heated, cooled or conditioned air is often insulated. Condensation due to humidity and differences in temperature between the air flowing in the ducting and the outside temperature can cause condensation, resulting in corrosion and mould problems. Another instance where such difficulties can arise includes insulated pipework in general, where a liquid such as water flows through the pipes and can promote condensation on the outside of the pipes that may leak underneath insulation layers.

Description of the Invention

The present invention provides a self-adhesive, air barrier, water vapour permeable tape. The tape is an air barrier, substantially or even completely preventing a flow of air there through. As understood in the construction industry an air barrier material may be defined as one that has been tested to have an air permeance of less than 0.02 l/(s-m ² ) @ 75 Pa (0.004 cfm/ft ² @ 1 .57 lb/ft ² ) in accordance with the ASTME Standard Test Method for Air Permeance of Building Materials.

The tape is water vapour permeable. A water vapour permeable sheet (membrane) can be defined as having a water vapour transmission resistance less than 0.6 MNs/g as measured according to BS3177. Water vapour permeability can also be expressed in terms of a moisture vapour transmission rate (MVTR) which is expressed in perms where 1 US perm is = 1 .0 grain/square-foot- hour- inch of mercury = 57.2 SI perms = 57.2 ng/s-m ² -Pa. When tested to ASTM E96 method B the tape of the invention has a permeability of > 1 US perm, > 57.2 SI perms or even >10 US perm, >572 SI perms. Alternative test methods such as Japanese standard JIS L 1099 may also be employed to assess water vapour permeability as shown hereafter with respect to tests results. The permeability units employed in JIS L 1099 A-1 are g/m ² /hr or g/m ² /24hr. Preferably the permeability measured by this method is > 100 g/m ² /hr. The tape is self-adhesive. Advantageously an adhesive layer covers the sheet material of the tape continuously, on the side to be fixed to a substrate. Advantageously the adhesive layer is of a pressure sensitive adhesive.

Advantageously the adhesive layer is of a water vapour permeable adhesive such as are known in the art. The adhesive may be an air and water vapour permeable adhesive. For example an air and water vapour permeable adhesive based on a pressure sensitive acrylate adhesive such as described in EP0397554 may be employed. To make such an air and water vapour permeable adhesive, an acrylic pressure sensitive adhesive in an organic solvent has water or water and an absorptive high molecular weight compound dispersed within it. The absorptive high molecular weight compound may be a water absorbent polymer, such as the so called super absorbent polymers known in the art. A crosslinking agent such as a polyfunctional isocyanate may be employed. A layer of the adhesive composition is made on a substrate (such as a release paper or the sheet material used to form the tape) and then a drying and/or curing step is carried out. This forms a continuous layer of an air and water vapour permeable pressure sensitive adhesive. On drying and/or curing, as the solvent is removed, the dispersed water and/or the dispersion of water swollen absorptive high molecular weight compound prevents the adhesive layer fusing together into a completely homogeneous layer. This results in the formation of tortuous microscopic pathways in the dried/cured adhesive layer, where the water or water swollen absorptive high molecular weight compound had been present, before the water is driven off by the drying/curing step. Partial coverage of an adhesive layer that is not necessarily water vapour permeable can allow a tape to be water vapour permeable and self-adhesive, but this is limited as the adhesive covered parts of the tape do not have good or perhaps any water vapour permeability. Such an approach can present difficulties in achieving effective sealing to a substrate and might therefore be less effective due to air infiltration. Partial coverage, for example coverage in a pattern of areas of the tape material with adhesive interspersed with areas of the tape material without adhesive is possible, but not generally preferred. The pattern of the adhesive may be as discrete patches or may be of, for example, an otherwise continuous adhesive layer with discrete patches where adhesive is absent.

The tape may be reflective. For example the tape may comprise a metallised film, for example an aluminized film. The film is water vapour permeable film so may, for example, be microporous or microperforated in nature. Metallised microporous or microperf orated films are commercially available. Generally a film of a plastic such as polypropylene has a metal layer deposited on it to form the metallised film. A metallised film forming at least one layer of the tape construction has the advantage of providing energy efficiency in terms of thermal efficiency, especially useful in applications such as a wall construction where high thermal efficiency is required. An alternative to a metallised film as a reflective layer may be a metal foil, for example a microperforated metal foil, typically an aluminium or aluminium alloy foil.

The reflective tape with moisture vapour permeability has a number of advantages. For example if prior art reflective but non vapour permeable tape is used on the outside (cold side) of insulation in a wall construction it prevents water vapour movement, encouraging condensation behind it. The trapped moisture can lead to lower thermal performance, rust, wood rot and de-laminating of the tape. Such delamination can also occur when non-permeable tape is used on air conditioning ducting, sometimes resulting in the tape having to be replaced within weeks to avoid further inefficiencies of leaking air as the tape has been rendered useless.

The tape material may be of a laminated construction (in addition to the presence of the adhesive layer) to provide the desired air barrier and water vapour permeable properties in a reasonably robust product. For example the tape may be a laminate comprising a reflective (metallised) microporous or microperforated film, or a metal foil, laminated to at least one other layer. The reflective (metallised) microporous or microperforated film may be of polypropylene. The other layer may be, for example a polypropylene spun-bond non-woven layer to which a continuous layer of pressure sensitive vapour permeable adhesive layer is applied. As usual with a self-adhesive tape, a layer of a release material, such as a silicone coated PET release sheeting may be provided to facilitate transport and use of the product. The tape may be of any width desired, depending on the detailed application envisaged. For example the tape may be supplied in widths of 50mm, 75mm. However any width may be contemplated and the tape may even be supplied as a self- adhesive sheeting material, of for example, up to 1 .5m in width. Wider sheets can be contemplated. The self-adhesive sheeting material may be used in any application, such as a building construction, for example behind a rainscreen, to provide a self- adhesive air barrier yet water vapour permeable material (optionally reflective for additional thermal insulation) for coating a surface. The tape may be employed in a variety of uses. The air barrier yet water vapour permeable tape provides essentially airtight sealing yet at the same time a route for water vapour migration, through the tape.

The present invention provides a method of sealing a joint between components; the method comprising applying a layer of a self-adhesive, air barrier, water vapour permeable tape, as described herein, over a joint between two said components, so as to provide a barrier to air flow, whilst allowing water vapour migration through the tape.

The joint between components is where two components are close to each other (adjacent), with or without a gap in-between. The components are not necessarily physically linked together e.g. by fastenings. The tape is used to cover the joint including any gap between the components.

Thus the present invention provides a wall or roofing construction comprising a thermal insulation layer;

wherein the insulation layer comprises a plurality of insulating boards laid to abut edge to edge;

wherein the insulating boards are substantially water vapour impermeable; and wherein the joints between adjacent boards are sealed by a self-adhesive, air barrier, water vapour permeable tape.

In such constructions the tape provides a route for moisture to escape. When the roof or wall is being constructed water, such as rain water, may be present within the insulation layer or another layer of the construction. The tape prevents air movement, this improving insulating efficiency. At the same time the tape provides a water vapour escape route, hence avoiding trapped condensation, and thus can avoid the potential for rot or rust.

In normal use, after the wall construction or roofing construction has been completed, water or water vapour may still find its way to the insulation layer, for example as a consequence of leakage in the structure, or even intentionally as part of the anticipated air and water vapour movements within the structure concerned. The use of a water vapour permeable tape aids in avoiding dampness at least within the layer of insulation.

This is particularly the case in rainscreen type wall constructions. They are designed to protect the structure from the majority of rain ingress but not fully. There is a drained cavity behind the outer cladding but moisture is still present in that cavity during and after rainfall, and air currents flow. Open joints would allow passage of air flow and moisture. Using the tape of the invention allows the inner insulation layers to keep out air flow but at the same time avoid condensation problems as the tape is breathable with respect to water vapour.

The insulating boards are substantially water vapour impermeable. Typical boards used for purposes such as partial filling of cavity walls, rainscreen cladding systems and external wall insulation may be formed from thermoset foams. For example polyisocyanurate or polyurethane foams that may be closed cell foams. Foam boards of this type may be provided with aluminium foil layers on one or both faces, to improve thermal insulation and increase fire resistance. Such boards may be effectively water vapour impervious, at least in the direction of from one face through to the other.

The boards are typically mechanically fixed to another layer of the wall or roof construction or fixed to support structures such as wooden or metal studs. In a cavity wall, the wall ties may be employed as fixings for the boards. Taping is applied to the external facing surface of the boards to seal over at the joints. In prior art constructions such taping is done using water vapour impervious tapes, such as aluminium foil tapes. Alternatively a fluid sealant/adhesive that sets to seal the joint may be used. These approaches can trap moisture, for example between a layer of wall (e.g. brick or block wall) and the insulation layer or between joints in the insulation layer. The boards may also be employed for internal insulation purposes, such as between studs in timber frame walls. In which case the tape of the invention may be employed, applied to the interior facing surface of the boards at the joints between abutting boards to allow moisture movement in the same way.

By using the air barrier water vapour permeable tapes described herein a route for water vapour movement is provided. Tapes with a metallised film are generally preferred because of their superior thermal insulation properties due to the reflective surface preventing radiative heat transfer. In other words the reflective surface has low emissivity (prevents radiative transfer there through). This is particularly so where the faces of the boards employed are covered with foil. Such boards are intended to have enhanced thermal insulation properties from the reflective surfaces. Sealing joints between adjacent boards with a non-reflective tape can compromise the thermal insulation properties of the construction as a whole as a relatively large proportion of the surface area of the reflective surface of the boards is covered by tape, which may be 50mm , 75mm or even wider to ensure effective sealing of the joint.

The present invention also provides a method of allowing moisture diffusion from a layer in a wall or roofing construction, the method comprising applying a self-adhesive, air barrier, water vapour permeable tape to joints or gaps in a said layer.

The present invention provides a method of sealing joints or gaps in the insulation of a duct construction, the method comprising applying a self-adhesive, air barrier, water vapour permeable tape to a said joint or gap, so as to allow diffusion of water vapour.

Heating, ventilation or air conditioning ducting in a building construction is often insulated, to avoid energy losses. The ducting may be insulated after installation or sections of ducting may be supplied pre-insulated. Condensation may collect on the (generally metallic) outer surface of the ducting, depending on the atmospheric conditions inside and outside the ducting (temperatures and water vapour contents). In addition condensation may form inside the ducting and leak to the outside at joints in duct sections. These condensation problems can lead to damage to the insulation and corrosion to the duct material. By using moisture vapour permeable tape of the invention on the joints or any other gaps in the ducting insulation an escape route for condensation is provided. Using a water vapour impermeable tape may result in the tape delaminating or simply falling off due to water damage.

The present invention provides a method of sealing joints or gaps in a duct construction, the method comprising applying a self-adhesive, air barrier, water vapour permeable tape to a said joint or gap, so as to allow diffusion of water vapour within the duct, to outside the duct the use of the tape. The air barrier properties of the tape keep the joint substantially air tight, but permeable to water vapour. Brief description of the Drawings

Figure 1 shows in schematic cross section a reflective self-adhesive, air barrier, water vapour permeable tape;

Figures 2 and 2A show in schematic perspective, the tape of figure 1 in use in a wall construction; and

Figure 3 shows in schematic perspective an insulated air conditioning duct. Description of Some Preferred Embodiments

Figure 1 illustrates in schematic cross section the layers of an air barrier, moisture vapour permeable self-adhesive tape. The tape 1 has a reflective layer 2 provided on a microporous film 4 of polypropylene. The reflective layer may be of aluminium or aluminium alloy and deposited for example by vapour phase deposition techniques on to the microporous film 4. It will be understood that the reflective layer 2 is itself porous, so as to allow moisture vapour through. The reflective layer 2 may be on top of the microporous film 4 as depicted, or integrated within the microporous layer 4. Laminated to the microporous layer 4 is a spunbond filamentous polypropylene layer 6. Alternatively the reflective layer or layers of the tape may be microperf orated so as to provide vapour permeability but still be classified as an air barrier.

A layer of air and moisture vapour permeable pressure sensitive adhesive 8 is applied to the spunbond layer 6. A release paper 9 is provided on adhesive layer 8, to be removed before use.

Figure 2 shows in schematic form part of a wall construction 10. Insulation boards 1 1 of a polyurethane foam and having aluminium foil faces are laid to abut one to another with joints 12 between short edges and joints 14 between long edges. They are supported by metal uprights 16 (studs) to which they will be fixed mechanically. Further outer layers in front of the boards 1 1 will complete the wall structure. Not shown in this view, but see figure 2A. A reflective air barrier, moisture vapour permeable self- adhesive tape 1 (for example, 50mm width) has been applied along some of the joints 12, 14 between boards 1 1 . In general all the joints 12, 14 will be covered by a tape 1 . The tape 1 allows moisture from the inside (studs 16 side) of the boards or trapped within the boards to escape outwards, even though the boards 1 1 are essentially water vapour impervious. The tape 1 is reflective by having a metallised outer layer. As shown, in cut away, in figure 2A the wall structure may be completed by further studs 16a and cross battens 17, supporting an outer cladding 18. For example outer cladding 18 may be a rainscreen cladding, which is not entirely waterproof .

Figure 3 shows an air conditioning duct 19 provided with a layer of metallised insulation 20 wrapped around it. Joints 21 between portions of insulation 20, or between ends of insulation 20 that meet on wrapping round the duct 19, are sealed by a metallised air barrier, moisture vapour permeable self-adhesive tape 1 . Moisture collecting on the outer surfaces of duct 19 may escape by permeating through the tape. Moisture may occur, for example by condensation within the duct 19 leaking out through joins in the ducting material 22. Alternatively condensation may occur on the outside of the ducting material 22, depending on the atmospheric conditions and the temperature of the duct 19. More generally, similar arrangements may be provided on any duct, conduit or pipe whether or not they are provided with a layer of insulation.

Test results

Table 1 , below, shows adhesion and water vapour permeability tests for an air barrier, moisture vapour permeable self-adhesive tape of the type shown in Figure 1 , discussed above. A 2gm ^"2 aluminium based coating 2 is provided on a 30 gm ^"2 layer of microporous polypropylene film 4 and a 53 gm ^"2 or 83 gm ^"2 layer of spunbond polypropylene 6. Adhesive layer 9 is an air and water vapour permeable acrylic based adhesive of the type described for example in EP0397554.

The test tape was manufactured in two weights about 85gm ^"2 and about 1 15gm ^"2 (before adhesive) depending on the weight of spunbond layer 6 employed. An adhesive weight of about 70 gm ^"2 was employed in making these tapes. Adhesion was measured according to Japanese standard JIS Z 0237. Adherend : SUS (steel) or GF(gypsum fibre board). Peeling test : 90 degree peel, 300mm/min.

The permeability to water vapour was measured according to Japanese standard JIS L 1099 A-1 . Temperature : 40 ^S C x 90% RH.

These results show a high water vapour permeability for the reflective, air barrier, moisture vapour permeable self-adhesive tape. The tape sheeting, without the adhesive layer, had permeabilities of 169.6 and 155.4 for the 85gm ^"2 and 1 15gm ^"2 test tapes, respectively. This shows the limited reduction in water vapour permeability of the product where an air and water vapour permeable adhesive is employed. Thus an air barrier yet highly water vapour permeable product is produced.

Table 1

Further testing on the 115gm ^"2 weight material was carried out as detailed below.

In respect of resistance to water vapour transmission, results are shown in Table 2 below, with the tape tested with either face, facing the high humidity.

Tests were made by the wet cup method in accordance with EN ISO 12572: 2001 , "Hygrothermal performance of building materials and products - Determination of water vapour transmission properties".

The sample was freely and continuously exposed to an atmosphere of 50 ± 2% relative humidity at 23 ± 2 ^S C for at least 24 hours prior to determining thickness and water vapour transmission properties. Each specimen was sealed to the open side of a test cup, containing an aqueous saturated solution (Ammonium dihydrogen phosphate, NH4H2P04), and placed in a controlled atmosphere of 23 ± 0.5 °C and 50 ± 3 % relative humidity. Each test cup has an effective test area of 50 cm ² . Due to the differential partial

vapour pressure between the test cup and the chamber, a vapour flow occurs through permeable specimens. Periodic weighings of the assembly were made to determine the rate of water vapour transmission in the steady state. Five specimens were tested on each face.

The conditions for testing were as described in Set C, i.e. 23 °C, 50 % R.H. in the environmental chamber and 93 % R.H. in the dish. The mean air pressure during the tests was 1002hPa. The air speed used during the test was greater than 2 m/s.

Table 2

Sample: 1 15g/m ²

EN ISO 12572 Set C - WATER VAPOUR TRANSMISSION

PROPERTIES

Reverse to high humidity Individual Results Mean S.D

Density of vapour flow 4.88 x 7.40 x 5.23 x 3.90 x 5.22 x 1.28 x rate, g kg/(m ² .s) 10 ^"6 10 ^"6 10 ^"6 10 ^"6 10 ^"6 5.33 x 10 ⁶ 10 ^"6

Water vapour permeance, 5.83 x 1 .15 x 6.46 x 4.27 x 6.44 x 2.71 x Wfc kg/(m ² .s.Pa) 10 ^"9 10 ^"8 10 ^"9 10 ^"9 10 ^"9 6.90 x 10 ⁹ 10 ^"9 Water vapour resistance, 1 .72 x 8.72 x 1.55 x 2.34 x 1.55 x 5.23 x Zc m ² .s.Pa/kg 10 ⁸ 10 ⁷ 10 ⁸ 10 ⁸ 10 ⁸ 1.61 x 10 ⁸ 10 ⁷

Water vapour diffusion

equivalent air layer 0.034 0.017 0.031 0.046 0.031 0.032 0.010 thickness, Sdc (m)

Thickness (mm)

0.52 0.46 0.45 0.44 0.49 0.47 0.03

Data that has been corrected for the resistance of the air gap between the base of the specimen and the saturated solution is indicated by subscript "c". These results also show the high rates of water vapour transmission in both directions, through the tape from the adhesive side and through the tape from the face side.

The 1 15g/m ² tape was also tested for water penetration resistance i.e. resistance to liquid water.

Resistance to Water Penetration

The resistance to water penetration, or water tightness, of the material was determined based on Method A of EN 1928: 2000, "Flexible sheets for waterproof ing - Bitumen, plastic and rubber sheets for roof waterproofing - Determination of watertightness", and modified by Clause 5.2.3 of EN 13859-1 : 2014. Specimens were conditioned for a minimum of 6 hours at 23 ± 5 °C. A specimen of 150 mm diameter (with filter paper, to indicate water passage, and a cover plate, to prevent material lifting, placed over the specimen) was subjected to a hydrostatic head of 200 mm for the specified period of 2 hours. The rate of increase of water pressure was set at 60cm per minute. Three specimens were tested and inspected for any discolouration of the upper filter paper. The sample was deemed to pass if no discolouration of the filter paper was observed on all three specimens.

Results are shown in Table 3 below. Table 3

Sample: 1 15g/m ²

The results demonstrate that the tape is water vapour permeable but provides a good barrier to liquid water.

Tensile strength testing is shown in Table 4 below.

Tensile Strength and elongation were determined following the procedure detailed in EN 1231 1 -1 : 2000, modified by Annex A of EN 13859-2: 2010. Specimens were conditioned for a minimum of 20 hours at 23 ± 2 °C and relative humidity in the range of 30 - 70 %.

Five specimens were prepared in each direction, each 100 mm wide and long enough to enable a gauge length of 200 mm to be used. The outer 25 mm along both of the longer edges of the specimen was folded inwards (towards the centre) so that they meet in the middle of the specimen but do not overlap. The tests were made on a Testometric C.R.E. machine fitted with flat faced jaws, set 200 mm apart and operating at a constant rate of extension of 100 mm per minute. A pre-tension of 5 Newtons was employed.

Tensile strength is quoted in Newtons per 50 mm when calculated as in Annex A. Individual values for tensile strength and elongation and the mean and standard deviation are given for each direction. Mean tensile strength is rounded to the nearest 5N and extension to the nearest %. Table 4

Samples of the 1 15g/m ² tape tested in accordance with EN ISO 1 1925-2: 2010 were classified according to BS EN 13859-1 & 2: 2010 as Class D.