Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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INSULATED AIR TRANSFER DUCT
This invention relates to an insulated air transfer duct and particularly
to a covering material which fully protects the insulation material.
BACKGROUND OF THE INVENTION
Exterior ducts for transfer of air between an interior location within a
building and an air management system exterior to the building, the duct
typically
comprise a metal duct wall defining a hollow interior through which the air
passes
between the interior location and the air management system with at least part
of the
metal duct wall exterior to the building and thus subject to the exterior
environment.
In order to reduce heat loss a layer of rigid insulation material surrounds at
least the
exterior part of the metal duct wall. This is particularly important in
locations where
extreme temperature differences are possible but is advantageous everwhere.
Existing alternatives for covering and protecting the insulation material
are as follows.
A layer of glass fiber and mastic (tar) is applied. This is a very old
technique for outdoor ventilation insulation protection. Insulation is
applied, followed
by a layer of mastic (tar) troweled on to the insulation, followed by a glass
fiber mesh
applied/embedded to the mastic followed by a final layer trowel coat of
mastic. This
application is still being used to date. It is plagued with leaks from the
date of
installation, and has no ultraviolet / ozone resistance. It is a very messy
application
with a very unappealing appearance.
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An aluminum Jacket is applied. This is another very old technique for
outdoor ventilation insulation protection. Insulation is applied, then an
aluminum or
stainless steel clad finish is applied over the insulation. Years ago the
cladding
would be bent and manipulated to fit with sheet metal equipment onsite. Each
piece
of cladding would then be joined together with screws or rivets and sealed
with a
bead of silicone caulking.
Over the years the fabrication equipment is no longer onsite and now
the cladding is being applied flat to all the 4 sides and affixed to the
insulation with
foil tape. The four sides (corners) of the cladded ducting now has matching
corner
beading applied and fastened with screws all around, followed by a bead of
silicone
caulking applied to all the joints. The joints break open over time causing
leaks, the
screw holes are never sealed causing seepage of water from the date of
installation.
The aluminum also dents from maintenance workers and hail.
This is the last alternative is sold under the trademark Ventureclad.
This is essentially a 2 feet wide roll of foil self-adhesive tape. It is a
peel & stick
application. This product is made to look like the aluminum jacket. Companies
often
quote aluminum but on site substitute this product because the appearance is
somewhat the same. This product is supposed to be applied with an overlap and
simply rubbing it down with a plastic applicator supplied with the product.
Because of
the little holes that would be visible on the top side of the ventilation
ducts from the
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edges unsticking over time. The mechanical insulators would simply apply a
bead of
aluminum (silver) caulking to all the joints. The manufacturer does not ask
for this to
be done. The trade's people do it to minimize call backs.
The other problems with this product is that birds (crows/ravens) will
peck holes threw the product. It also shows hail damage easily and can be
damaged
by maintenance workers. Also because the duct installers seldom seal the
ventilation ducts 100%, the leaking air from the duct acts to create a
ballooning
effect on the product which looks totally unsightly and causes it to pull away
from the
insulation layer underneath.
SUMMARY OF THE INVENTION
According to the invention there is provided an air duct transporting air
between an interior location within a building and an air management system
exterior to the building, the duct comprising:
a metal duct wall defining a hollow interior through which the air
passes between the interior location and the air management system with at
least an
exterior part of the metal duct wall subject to an environment of extreme
temperature
difference and/or extreme humidity;
a first sheet assembly surrounding at least the exterior part of the
metal duct wall;
the first sheet assembly comprising a layer of rigid insulating material
and an exterior covering foil layer laminated thereto;
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the first sheet assembly being attached to the exterior part of the metal
duct wall by pins which project through the exterior covering foil layer and
the layer
of rigid insulating material and attached to the metal duct wall to define
exterior
heads of the pins exterior to the foil layer;
and a covering material surrounding the first sheet assembly;
the covering material comprising a laminate of two layers of a plastics
material including an intermediate layer of fibers;
the covering material being free from a foil layer;
the covering material being bonded to the exterior covering foil layer of
the first sheet assembly by a-self-adhesive material laminated to an inner
surface of
the covering layer so as to be carried thereby;
the covering material covering the heads of the pins.
Preferably the thickness of the plastics layer is less than 1.5 mm or
0.060 inch and more preferably of the order of 1.2 mm or 0.045 inch or of the
order
of 0.9 mm or 0.035 inch. These thicknesses have been found to allow the
material
to wrap around square corners of a rectangular duct while remaining attached
toe h
exterior foil layer of the insulation on either side of the corner.
Preferably the plastics layer comprises a polyester such as PET and
comprises a laminate of polyester including an intermediate layer of fibers
forming a
reinforced continuous polyester fibre arranged in a grid or in a mat
sandwiched
between two sheets of flexible matrix.
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Preferably the plastics layer has a coating of adhesive having a
thickness of the order of 0.3 mm or 0.011 inch.
Preferably the seams are heat bonded and/or the seams are coated
with a set liquid material extending to each side of an exposed edge of the
material
at the seam.
The arrangement of the present invention is designed to protect
exterior insulation applied to rooftop ventilation systems. It is a weather
protection
jacketing using thermoplastic polyolefin (TPO) technology.
TPO is a waterproof sheet membrane which consists of a reinforced
continuous polyester fibre arranged in a grid or in a mat sandwiched between
two
sheets of flexible matrix, a kind of polymer waterproof material which is made
of
advanced processing technology. TPO membranes provide both the ethylene
propylene diene rubber weather resistance, aging resistance and polypropylene
weld ability. One of the properties of thermoplastic membranes is that the
material
temporarily changes from a semi-solid state when heated sufficiently, enabling
the
sheets that are overlapped to be fused together and return to a solid upon
cooling.
Thus, a monolithic, continuous sheet membrane is created.
Advantages of the present arrangement include:
--a heat-welded technology for a continuous waterproof sheet
membrane;
--Easy peel and stick application
--Weather resistant
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--Anti-aging resistant
--Anti-ultraviolet,
--ozone resistant
--High puncture & impact resistant. (excellent tear resistant)
--Inherently fire resistant.
--Water resistant
--Low temperature resistant (remains flexible at low temperatures)
--High temperature resistant
--Resistance to solvents, oils, acids, and detergents.
--Resistant to bacteria & fungus/mold growth.
--Easy to bend and manipulate around "inside/outside" corners and
shapes.
--Aesthetically appealing. (preferably white)
--Provides excellent visual feedback of workmanship during and after
installation.
The TPO waterproof membrane (PET surface) is polyester reinforced
smooth with a peel and stick adhesive backing. The material is supplied in a
roll
size of 1.2mm thickness (47.24 mil) x 1 meter width x 20m length. The TPO
comprises a waterproof membrane of 0.9mm thickness or 35.43 mil with an
adhesive layer of 0.3mm sensitive pressure adhesive glue or 11.81 mil. The
glue
backing is peel Bitumen rubber glue.
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BRIEF DESCRIPTION OF THE DRAWINGS
One embodiment of the invention will now be described in conjunction
with the accompanying drawings in which:
Figure 1 is a longitudinal cross-sectional view of a duct according to
the present invention.
Figure 2 is a transverse cross-sectional view of the duct of Figure 1.
Figure 3 I an enlarged view of the cross-section of Figure 2.
Figure 4 is an enlarged cross-section through an overlap joint of the
covering material of the duct of Figure 1.
In the drawings like characters of reference indicate corresponding
parts in the different figures.
DETAILED DESCRIPTION
The air duct 10 of Figures 1 and 2 acts for transporting air between an
interior location 11 within a building and an air management system 12 such as
a
heating, cooling or air exchange system exterior to the building.
The duct includes a metal duct wall defining a hollow interior through
which the air passes between the interior location and the air management
system.
IN the embodiment shown the duct is square but other rectangular shapes or
other
cross-sections are possible including circular.
At least part of the metal duct wall is subject to an environment of
extreme temperature difference and/or extreme humidity or weather as provided
by
the exterior or by high humidity locations.
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A layer 14 of rigid insulation material surrounds the exterior part of the
metal duct wall and is typically fabricated from stiff panels 14A, 14B, 14C
and 14D
which are cut to size to fit together to cover the outside surface of the
duct. The
insulation material is typically fastened to the duct by pins 15 passing
through the
insulation material to the exterior surface of the duct. The rigid insulation
material
comprises the stiff fibrous layer 17 and a foil exterior layer 16.
The outside surface of the insulating material is in the present
invention covered by a covering material 20 wrapped so as to surround the
rigid
insulation. The covering material comprises a self-adhesive plastics layer 20
bonded to an exterior surface of the rigid insulation.
The covering layer 20 comprises a plastics layer which is a laminate of
polyester layers 21 and 22 including an intermediate layer of fibers 23. The
plastics
layer has a coating of adhesive 24 which is pressure sensitive and is covered
before
application by a release sheet.
The covering material is wrapped round the duct with overlapped
seams 25. The seams can be heat bonded as indicated at 26 and coated with a
set
liquid material 27 extending to each side of an exposed edge 28 of the
material at
the seam.
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