Note: Descriptions are shown in the official language in which they were submitted.
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ADHERENT WATER VAPOUR PERMEABLE AIR AND MOISTURE BARRIER
SHEET MATERIAL
FIELD
[0001] The present invention relates to building materials, and more
particularly to air and water resistive barriers.
BACKGROUND
[0002] In construction, air barriers control air leakage into and out of
the
physical separator between the interior and exterior of a building. Known air
barriers may be interposed between layers of the building structural wall. Air
barriers are typically also water resistive and often take the form of
membranes
or house wraps and provide a defined air permeance rate.
[0003] Some air barriers are also water vapour permeable, allowing the
passage of water vapour while preventing the passage of air. This is made
possible because the molecular structure of water vapour allows it to pass
through smaller pores than oxygen and nitrogen.
[0004] Water vapour permeable air barriers in membrane form are available
from numerous manufacturers including Du PontIm (TyvekTm Homewrap) and
FiberwebTM (TyparTm Housewrap). Self-adhering water vapour permeable air
barriers in membrane form are also available from numerous manufacturers
including the Henry Company and WR Grace and Co.
[0005] Existing barrier membranes typically include a water vapour
permeable
membrane coated on one side by an adhesive. In order to form a a substantially
airtight building enclosure, sheets of the membrane are affixed to the
building in
1
an adjacent or overlapping relationship to form a building envelope. The
overlapping of membranes often does not work well, as the adhesive used to
affix the barrier membranes does not adhere well to other membranes. Seam
tape may instead be used to ensure continuity of the air barrier/building
envelope, but is cumbersome.
[0006] Thus, properly positioning and adhering adjacent sheets of material
in
order to form an air tight envelope around the building structure remains a
challenge.
[0007] Accordingly, new water vapour permeable air tight barriers allowing
formation of a better sealed building envelope are desirable.
SUMMARY OF THE INVENTION
[0008] In accordance with an aspect, there is provided a water vapour-
permeable building sheet material comprising segments installed in overlapping
relationship against a building structure, wherein each of said segments
comprises: a water vapour permeable membrane having first and second
opposing surfaces, wherein surface energy of said second opposing surface is
less than 35 mN/m; an adhesive layer that is vapour permeable, and pre-applied
to the entirety of said first opposing surface prior to installation of the
water
vapour preamble of said water vapour membrane; an adhesive region comprising
at least one strip of adhesive pre-applied to the second opposing surface, to
extend lengthwise parallel and proximate its edge prior to installation of the
water
vapour preamble membrane; wherein at least one strip of adhesive of said
adhesive region of a first segment of said sheet material bonds to the
adhesive
layer of a second segment of said sheet material when said second segment of
said sheet material is placed in overlapping relationship with the at least
one
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strip of said first segment, without precise alignment, to form an air
impermeable
boundary between said two of said segments, preventing lateral migration of
air
between said two of said segments.
[0009] In accordance with another aspect, there is provided a method of
applying a water vapour-permeable building sheet material to a building
structure
comprising: forming a plurality of sheet segments of the sheet material each
of
the sheet segments comprising a water vapour permeable membrane having first
and second opposing surfaces; an adhesive applied discontinuously to the first
face of the adhesive to provide uncovered regions, exposing the membrane to
allow water vapour to permeate therethrough; an adhesive region applied to the
second opposing surface, wherein the surface energy of the second opposing
surface is less than 35 mil/1'n; placing two sheet segments of the sheet
material in
overlapping relationship on the building structure so that adhesive applied to
the
first face of the material of one of the two sheet segments may mate and bond
with the adhesive region applied to the second opposing face of the other of
the
two sheet segments to form a substantially air impermeable boundary between
the two sheet segments to prevent lateral migration of air between the two
sheet
segments.
[0010] In accordance with yet another aspect, there is provided a building
envelope comprising a plurality of sheet segments of said sheet material each
of
said sheet segments comprising a water vapour permeable membrane having
first and second opposing surfaces; an adhesive pre-applied discontinuously to
said first opposing surface of said adhesive to provide uncovered regions,
exposing said membrane to allow water vapour to permeate therethrough; an
adhesive region pre-applied to the second opposing surface, wherein surface
energy of said second opposing surface is less than 35 mN/m; wherein sheet
segments of said sheet material are placed in overlapping relationship on said
building structure such that the adhesive pre-applied to said first opposing
surface of said material of a first of said sheet segments mates and bonds
with
the adhesive region pre-applied to said second opposing surface of an adjacent
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one of said sheet segments to form an air impermeable boundary between said
adjacent sheet segments to prevent lateral migration of air between said sheet
segments, so that the air leakage of said building envelope does not exceed
0.2
1/s/m2 at a pressure difference of 75 Pa after wind pressure conditioning when
tested in accordance with ASTM E-2357.
[0010a] In accordance with yet another aspect, there is provided a water
vapour-permeable building sheet material comprising segments adhered in
overlapping relationship against a building structure, wherein each of said
segments comprises: a water vapour permeable membrane having first and
second opposing surfaces, wherein surface energy of said second opposing
surface is less than 35 mN/m; an adhesive layer that is vapour permeable, pre-
applied to cover the area of said first opposing surface of said membrane,
with
between 1% and 99% of adhesive; an adhesive strip pre-applied to the second
opposing surface parallel to a lengthwise extending edge of said sheet
material;
a first removable film, coating said adhesive on said first opposing surface;
a
second removable film, coating said adhesive region on said second opposing
surface; wherein at least one strip of said adhesive region of a first segment
of
said sheet material bonds to the adhesive layer of a second segment of said
sheet material when said second segment of said sheet material is placed in
overlapping relationship with the at least one strip of said first segment,
without
precise alignment, to form an air impermeable boundary between said two of
said segments, preventing lateral migration of air between said two of said
segments.
[0011] Other aspects and features of the present invention will become
apparent to those of ordinary skill in the art upon review of the following
description of specific embodiments of the invention in conjunction with the
accompanying figures.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0012] In the figures which illustrate by way of example only, embodiments
of
the present invention,
[0013] FIG. 1 is a perspective view of sheet material of water vapour
permeable building membrane, exemplary of an embodiment of the present
invention;
[0014] FIG. 2 is a schematic view of the overlay of two sheet segments of
the
sheet material of FIG. 1;
[0015] FIG. 3 is a schematic view of the adhesive interface between two
sheet
segments of FIG. 2;
[0016] FIGS. 4 to 6 are cross-sectional views of exemplary sheet material;
[0017] FIG. 7 is a perspective view of a building structure with a water
vapour
permeable building membrane applied;
[0018] FIG. 8 is a cross-sectional view of the building structure of FIG.
7;
[0019] FIG. 9 is a perspective view of water vapour permeable building
membrane exemplary of another embodiment of the present invention;
[0020] FIG. 10 illustrates a continuous sheet formation arrangement that
may
be used to form the sheet material of FIGS. 1 to 6; and
[0021] FIGS. 11 and 12 are perspective views of rollers used in the
arrangement of FIG. 10.
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DETAILED DESCRIPTION
[0022] FIG. 1 is a perspective view of sheet material 10 of a water-
resistive
vapour permeable air barrier building membrane, exemplary of an embodiment of
the present invention. Sheet material 10 is further shown in cross-section in
FIG.
4.
[0023] As illustrated, sheet material 10 includes multiple layers. As
depicted,
sheet material 10 includes a membrane 12 having a discontinuous adhesive 14
applied on one side. Membrane 12 is vapour permeable, but air impermeable. It
also acts as a water-resistive barrier. To that end, membrane 12 may have
micro-pores, and be formed of fiber or film having pores ranging from about
0.01
to 10 pm in size.
[0024] Membrane 12 may be formed of a spun-bond polymer, such as spun
bond polyethelyne, polypropelene, a suitable polymer film, a combination of
spunbonded or needlepunched substrates with a polymeric coating, or the like.
Membrane 12 may have any appropriate thickness, and is typically between
about .1 mm and 5 mm thick. As will become apparent, in some embodiments,
membrane 12 may comprise multiple layers.
[0025] An adhesive 14 is applied to the rear (i.e. first) face of membrane
12
using a roller or other applicator to provide a vapour permeable adhesive
layer,
as described below.
[0026] Example adhesives, suitable for use as adhesive 14 include solvent
based adhesives; polymer dispersion adhesives (water based); pressure
sensitive adhesives (e.g. butyl based hot-melt adhesives: ; or acrylate based
polymer disposing adhesives, etc.); hot-melt adhesives (e.g. pressure
sensitive
adhesives); reactive adhesives (e.g. one-part adhesives with moisture or heat
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based curing, or multi-part adhesives); natural adhesives (e.g. protein-based
bio-
adhesives); acrylic polymer or other synthetic adhesives. Typically, a hot-
melt
adhesive or a polymer dispersion adhesive is used as adhesive 14.
[0027] Adhesive 14 may itself be vapour permeable, and may be applied to
the entire rear side of membrane 12, or a portion thereof. Alternatively,
adhesive
14 may be applied in a discontinuous layer - so as to leave uncovered regions
on
sheet material 10. Regions on membrane 12 not covered by adhesive 14 are
exposed to allow the passage of water vapour through membrane 12, while
regions covered by adhesive 14 prevent the passage of water vapour through
membrane 12. The ratio of regions covered and uncovered by adhesive 14
influences the vapour permeability of membrane 12. In the depicted
embodiment, adhesive 14 is applied in sets of generally diagonal stripes, with
one set transverse to the other to form a diagonal checker pattern. Other
patterns are, of course, possible and will be apparent to those of ordinary
skill.
Adhesive 14 allows membrane 12 to be adhered to a building structure. In an
embodiment, between 1% and 99% of the surface of membrane 12 are covered
by an adhesive 14, that is otherwise vapour impermeable.
[0028] Typically, adhesive 14 is applied when its viscosity is relatively
low ¨
typically when it is hot, or in a spray - but remains tacky after application
to
membrane 12. In this way, adhesive 14 may be used to adhere membrane 12 to
another substrate ¨such as a building structure ¨ simply by applying pressure.
[0029] A removable protective film 16 is lightly adhered to the layer of
adhesive 14 for easy removal as sheet material 10 is installed on a building
or
structure as described below. Protective film 16 may be formed of paper or a
thin polymer film or the like.
[0030] As will be generally, understood, for an adhesive such as adhesive
14
to be effective it must properly adhere to an underlying surface. As noted,
adhesive 14 when hot or fluid is well suited to adhere to membrane 12. When
cool, adhesive 14 remains tacky, and remains well suited to adhere to a
building
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frame that is typically formed of wood. However, such adhesion depends largely
upon surface phenomena¨adhesive 14 must appropriately interact with the
surfaces to be joined: it should make intimate contact with the surface.
Different
adhesives use different mechanisms to flow and achieve contact ¨ structural
adhesives are typically low viscosity liquids before curing, hot melt
adhesives are
heated to a flowable viscosity at application, and pressure sensitive
adhesives
make use of their unique viscoelastic nature to flow.
[0031] The ability of an adhesive to adhere to a particular surface is
further
strongly influenced by the nature of the surface. For example, the chemical
make-up of the surface, the texture, porosity, and any contamination that coat
the
surface of the substrate (such as mold release agents, process additives which
bloom to the surface, or contaminants from handling) can all affect an
adhesive's
ability to flow and achieve intimate contact.
[0032] Even if cleaned, some surfaces may inherently resist being wetted by
an adhesive. This is often explained by a phenomenon referred to as surface
energy, described above.
[0033] Surface energy is the excess energy that exists at the surface (as
opposed to the bulk) of a solid. This excess energy exists because molecules
at
the surface cannot interact with as many like neighbours as molecules in the
bulk
are able to do; therefore, they have excess interaction energy. The surface
energy of a solid varies with its chemical make-up. Metals and glass, for
example, have a high surface energy and are easier to bond; whereas plastics
have a lower surface energy and are harder to bond.
[0034] Hardest of all are low surface energy plastic, such as
Polytetrafluoroethylene (PTFE) (Surface Energy 18.5 mN/m); Silicone 24 mN/m;
Poly(vinylidene fluoride) 25; Polyethylene (PE) 31mN/m; Polypropylene (PP) 31
mN/m; Polystyrene 33 mN/m.
[0035] Surface tension exists because molecules in the bulk liquid are in a
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lower energy state than at the surface. The interaction of liquid adhesive on
a
solid surface depends on the relative surface energy of the adhesive and
solid. If
the adhesive has a higher surface energy the adhesive will prefer to maintain
its
spherical form. In such circumstances, an adhesive will not spread and make
intimate contact with the surface to be bonded; rather, the molecules of the
liquid
adhesive will tend to remain associated with themselves, resulting in lower
bond
strengths. If, however, the surface energy of the adhesive is less than that
of the
substrate the adhesive will spread, thus making the intimate contact necessary
for good bonding.
[0036] Typically membrane 12 (or at least its forward face) is made of a
material having low surface energy (e.g. below 35 mN/m). Example materials
and their tabulated surface energies are Polyethylene (PE) 31 mN/m;
Polypropylene (PP) 31 mN/m. Other materials will be apparent to those of
ordinary skill. Thus, due to the low surface energy, membrane 12 is inherently
difficult to adhere to.
[0037] Not surprisingly, adhesives that generally adhere very well to
common
construction surfaces like plywood, OSB, concrete, glass, aluminium, etc. will
not
adhere very well to materials having such low surface energy. While such
adhesive adhere well to low surface energy materials when applied in the
factory
(due to the fact that the adhesive is being applied as a hot-melt, in hot and
liquid
form, or as a dispersion adhesive in dispersion form where it has a low
viscosity
and can easily penetrate into the surface texture of the membrane), they will
typically not adhere as well to such surfaces during field installation.
Simply, the
adhesive now has a higher viscosity and cannot easily penetrate into the
surface
texture of the membrane.
[0038] Low adhesion strength in areas where sheet material 12 overlaps with
other sheet material 12 can lead to separation between the segments of the
sheet material, compromising the continuity of the air barrier layer, as
described
below.
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[0039] A further adhesive region in the form of a strip 18 is applied to
the front
side of membrane 12, proximate a first edge 30 of sheet material 10. Strip 18
extends along the length of sheet material 10, but only occupies a fraction
(e.g.
between 2% and 5%) of the front of sheet material 10. Strip 18 extends along
the length of sheet material 10, generally parallel to edge 30. Strip 18 may
be
formed of one continuous stripe of adhesive, or multiple adjacent thin
stripes, or
any other suitable pattern. Again, a hot melt adhesive, pressure sensitive
adhesive, or dispersion adhesive, like that used as adhesive 14 may be used to
form strip 18. A further removable protective film 20, often referred to as a
release liner, covers strip 18, and may be removed as sheet material 10 is
installed, again, as described below. Again, removable protective film 20 may
be
formed of paper or a thin polymer film.
[0040] Sheet material 10 is typically of indefinite length, and extends
width-
wise between edges 30 and 32. In a typical embodiment sheet material 10 may
be rolled and cut width-wise from edge to edge (i.e. from edge 32 to edge 30)
into sheet segments of defined length based on application. The width of sheet
material 10 is also arbitrary ¨ and may for example be between about 1.0m and
3.0m. Sheet material 10 of width 1.5 m is convenient for transport and
handling.
Strip 18 generally extends along the entire length of sheet material 10, and,
for a
1.5 m wide sheet, may have a width of between about 2 cm and 25 cm, and may
be spaced between about 2 and 10 cm from edge 30.
[0041] In other embodiments membrane 12 may be a multi-layer membrane,
as for example, exemplified in FIGS. 5 and 6. As illustrated in FIG. 5, a
membrane 12' may be formed of a thin film 12a having micro-pores (having a
mean diameter of several microns), or otherwise of sufficient size to allow
water
vapour to pass. A discontinuous layer of adhesive 14' (like adhesive 14) may
be
applied to thin film 12a. Again, a thin protective sheet 16' may be removably
applied to adhesive 14'. A spun bond layer 12b (like membrane 12) is further
bonded to thin film 12a to form membrane 12'. Again an adhesive strip 18' like
strip 18 may be applied to the face of spun bond layer 12b, and covered by
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protective film 20' (like film 20).
[0042] In a further embodiment, depicted in FIG. 6, membrane 12" is formed
of a film 12e sandwiched between two spun bond layers 12c and 12d. Again an
adhesive stripe 18" like stripe 18 may be applied to the face of spun bond
layer
12'. A discontinuous layer of adhesive 14' (like adhesive 14) may be applied
to
thin film 12c. A thin protective sheet 16" may be removably applied to
adhesive
14". An adhesive strip 18" (like strip 18) may be applied to the face of spun
bond layer 12d, and covered by a removable thin film 20" (like film 20).
[0043] In yet a further embodiment depicted in FIG. 9 adhesive 14 (FIG. 1)
may be replaced with a puddle coated adhesive 44 on sheet material 10"
creating random regions of membrane 12" (like membrane 12 or 12' or 12")
covered by adhesive 44. Again, the size and relative distribution of regions
not
covered by adhesive 44, and the vapour permeability of adhesive 44 will
influence the overall vapour permeability of the resulting sheet material 10".
Again, between 1% and 99% of the surface of membrane 12" may be covered
with adhesive 44.
[0044] Sheet material 10 (or sheet material 10', 10" or 10'") may be
installed
on a building, as best illustrated in FIGS. 2, 3 and 7.
[0045] As illustrated in FIG. 7, sheet material 10 may be unrolled, cut
along its
width, and applied to a building 100 in generally vertically or horizontally
extending sheet segments 11a, 11b, 11c, etc. (individually and collectively
strip
segments 11) to form a building envelope. Typically sheet segments 11 are
applied to a frame 102 of building 100, beneath an outer cladding 104. As
illustrated in FIGS. 2, 3 and 7 and 8, sheet segments 11 are placed in side by
side, overlapping relationship.
[0046] Specifically, as illustrated in FIG. 2 and 8, after cutting sheet
material
into a sheet segment 11c, protective film 20 is removed from sheet segment
11c, and sheet segment 11c is applied to frame 102 (FIG. 7). Sheet segment
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11c may be applied proximate the bottom of a face of frame 102. A roller or
similar tool (not shown) may be used to press on membrane 12 of sheet segment
11c to tightly adhere the exposed adhesive 14 of sheet segment 11c to the
building structure.
[0047] Once affixed to frame 102, protective layer 20 of strip 18 of
segment
11c may be removed, and a further sheet segment 11b may be applied to frame
102. In particular, edge 32 of sheet segment 11b is placed to overlap with
sheet
segment 11c. The overlap should be sufficient to cover the adhesive in strip
18
of sheet segment 11c. In this way, adhesive 14 on the bottom of sheet segment
llb adheres to adhesive strip 18 on the face of sheet segment 11a.
[0048] The front surface of each of membranes 12, 12', 12" and 12" has a
surface tension less than about 40 mN/m, making adherence by adhesive 14
thereto difficult.
[0049] Conveniently, adhesive 14 of one sheet segment 11c and adhesive 18
of sheet segment 11b form a boundary that extends along the length of the
sheet
segment 11b, best illustrated in FIG. 3 and 8, that seals adjacent sheet
segments
to each other, to prevent lateral migration of air out of the building
envelope
between sheet segments 11, along their lengthwise extending edges. In the
absence of adhesive strip 18, adherence of adhesive 14 to the face (i.e.
directly
to membrane 12) of an adjacent sheet segment would be imperfect, because of
the low surface energy of the front surface of membrane 14 to which adhesive
14
would be adhering.
[0050] As will be appreciated by those of ordinary skill, ICC AC38 requires
that the air leakage rate of an air barrier membrane material not exceed 0.02
1/s/m2 at 75 Pa when tested according to ASTM E-2178. Likewise, the Air
Barrier
Association of America (ABAA) requires the air leakage rate of a wall assembly
with an air barrier membrane not to exceed 0.2 Ifs /m2 at a pressure
difference of
75 Pa in both directions after wind pressure conditioning when tested
according
to ASTM E-2357.
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[0051] While the criteria set out in the ASTM E-2178 test are relatively
easy to
achieve (only the membrane itself gets tested, so no installation details like
overlaps are being considered), the requirement for the assembly test as per
ASTM-E2357 is much harder to achieve since overlaps of the air barrier
membrane as well as a number of different penetrations are mandated in the
test
method.
[0052] Conveniently, a building envelope as described above may meet both
ASTM E-2178 and ASTM-E2357 criteria.
[0053] Sheet material 10 may be formed using conventional sheet forming
rollers as illustrated in FIG. 10. As illustrated, membrane 12 is fed from a
roll of
material through rollers 52a and 52b. Roller 52b has a patterned applicator
surface 54 illustrated in FIG. 11. Applicator surface 54 ensures that hot melt
adhesive 14 (stored in tank 56) is applied to only a portion of the bottom
surface
of membrane 12. Rollers 62a and 62b apply adhesive strip 18 to the top surface
of membrane 12. Roller 62b depicted in FIG. 12 includes an applicator to form
adjacent stripes. Protective sheets 16 and 20 are fed from rolls and applied
downstream by rollers 72a and 72b, to cover adhesive 14 and strip 18.
[0054] Of course, the above described embodiments are intended to be
illustrative only and in no way limiting. The described embodiments of
carrying
out the invention are susceptible to many modifications of form, arrangement
of
parts, details and order of operation. The invention, rather, is intended to
encompass all such modification within its scope, as defined by the claims.
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