Note: Descriptions are shown in the official language in which they were submitted.
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INSULATING ~OAM BUILDING PANEL AND METHOD
OF CONSTRUCTION UTILIZING SUCH PANELS
BACKGROUND OF THE ~NV~NTION
The present invention relates to heat insulating
panels which are comprised of a core of foam material for
use in construction of heat insulated building stx-~ctures,
such as built-up roofs, and more particularly to an
improved heat insulating panel which manifests
reduced curling under the heat of the sun.
The use of foamed plastic material for insulating
purp~ses in building structures such as exterior or
paxtition walls, bulk heads, ceilings, floors, storage
tanks, and roof structures is well known as such foamed
plastic materials have a very low thermal conductivity.
Such foam plastic materials having low thermal conductivity
for instance may comprise phenolic foam material such
as for example thermoset phenol formaldehyde materials.
ther low thermal conductivity foam materials comprise
poly-styrene foam and/or urethane foam.
The foam materials used as roofing insulation
have a density of about 1.5 to about 6 lb/~t3 so as to
have sufficient strength to support persons and their
equipment.
Typically, in such construction applications, the
foam material is sandwiched b~tween a pair o~ protective
skins, such as for example paper or paper composites.
The protec~iye s~ins serve as a convenient means of making
the heat insulating panels,as well as ~o protect and
maintain the integrity of the sandwiched foam material.
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One problem experienced with respect to such heat
insulating panels of the prior art, such as roofing
panels, is curling or warping of the panel. More particu-
; larly, during the construction of built up roofs'employing such heat insulating roofing panels, the
insulation panels are initially applied with a suitable
adhesive.to the supporting structure, such as for example a
corrugated steel roof deck, and'then bituminized roofing
materials are applied over roof insulator panels to
complete the roof structure. ~owever, from the time
the panels are applied on the roof support structure
until the application of.roofing materials thereover,
the panels curl under the heat of the sun. For
example, with two inch thick roofing panels constructed of
open celled phenolic foam material sandwiched between a
pair of paper media, c~rling of up to one inch can
result under the heat of the sun on a very hot-day. '
It is desirable to minimize the amount of curling
before the application of roofing materials thereon,
in order to assure a reasonably flat support on which
the com,ponents of the roofing membrane can be applied.
SUMMARY OF THE INVENTION
, In accordance with the present invention, there is . ,
provided an improved heat insulating panel, such as for
example a roofing panel or an insulating sheathing panel, ,
which manifests reduced curling,or warpage of the panel
after being applied on a supporting structure and before
application of inishing materials thereover, and. .
as such'overco~es some of .the above discussed and other
disadvantages.of the.prior art. More. particularly; in -
accordance with the present invention, the improved heatinsulating panel comprises first and second oppositely
disposed surfaces having a core therebetween comprised of
heat insulating foam material. One of the oppositely
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disposed surfaces includes a thin l~yer of reflecting
material over substantially the entire surface ther.eof to
. reduce the heat conveyed to the core due to sun radiation
.when the insulating panel is exposed to sun radiation
during the construction or the renovation of a
building structure.
In this regard, with many suitable foam materials,
such as phenolic foam materials, which meet the mechanical.
and heat insulating performance requirements for building
structures, the oam materials have a tendency to retain
moisture which, given enough time, reaches
equilibrium with.the atmospheric vapor partial
pressure. ~or example, such foam materials may have
: ....... the characteristic of absorbing and retaining up to
10~ moisture by weight when in an environment at 50% relative
.humidity at room temperature.
Consequently, when the heat insulating panels
are exposed to sun radiation after being applied to a
supporting structure and before application of.the
finishing materials thereover, the sun radiation may
heat up the exposed surface of the panel. The resulting
heat gradient established in the panel in turn may
have the tendency to dri~e the moisture in the panels from
the hot side of the panel to the relatively cool side of
the panel, thereby causing shrin~age of the top exposed . -
side of the panel and swelling and/or expansion of the lower
side of the panel. .This can thus result in the aforemen-
tioned curling--problem experienced in the prior art.
~owever, with the present invention, during the
construction of the building structure, the heat insu-
lating panels are adhered to the supporting structure. In
this manner, the sun radiation is reflected away from the
core of foam material, so that the temperature
differential across the panel is reduced. Consequently,
warpage or curling of the panels .
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is substantially reduced so that the finishing
materials such as roofing materials when the panels
. are supported on a roof support structure, may be
.easily applied over the surface of the heat insulating
panels.
More particularly, and in accordance with the
preferred embodiment, the thin layer of reflecting
material comprises a thin layer of aluminum foil on the
one surface of the panel. Still more particularly, the
core of foam material is sandwiched between a pair of
protective skins, each of which may comprise a corrugated
medium of kraft, semi-chemical or similar paper having a
liner attached to one side thereof remote from the core.
The aluminum foil is adhesively secured to the liner
of one of the protective skins so as to substantially
overlie one.of the outer surfaces of the panel. ~or
example, the thin layer of aluminum foil may be secured
with a neoprene adhesive or other high wet strength
adhesive.
In accordance with another aspect of the present
invention, there is disclosed a method of constructing a
heat insulating structure which comprises of the steps of
providing a plurality.of heat insulating.panels, each of
which includes a thin layer of reflecting material over
substantially the enti~e surface of one side of the panel,
applying the plurality of heat insulating panels on a
building support structure so that the layer of reflecting
material on the.first surfaces is exposed to the sun
radiation which may be present, whereby the thin layer
of reflecting material serve-s to reduce heat conveyed to
the core of the panel when sun radiation is present, and
then applying at least one layer of finishing material
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over the supported panels to thereby substantially
cover the reflecting material. In this way, the
problem of wa~ping ox curling of the panels prior to
the application of the finishing material thereover
is minimized.
These and other features and characteristics of the
present invention will be apparent from the following
detailed'description in which reference is made to the
enclosed drawings which illustrate a preferred embodiment
of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an enlarged cross-sectional elevation in
perspective of a protective skin employed in the heat
- insulating,panel in accordance with the present invention,
with the protective skin having a thin layer of reflec!ting
material applied to the outer surface thereof.
Figure 2 is an enlarged cross-sectional elevation in
perspective of a heating insulating panel employing the ' '
protective skin shown in Figure 1 to define one surface
thereof in accordance with the present invention.
Figure'3 is a cross-sectional elevation illustrating
- ' the, heat insulating panel in accordance with the present '
invention supported on a roof supporting structure
and having roofing material applied thereover to form
a composite built-up roofing structure.
DETAILED-DESCRIPTION OF THE PREFERRED EMBODIMENT
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Referring now to the drawings wherein like reference
characters rep~esent like elements, there is shown in
Figure 1 a protective skin 12 used in forming a composite
heat insulating panel 10 in 'accordance with the present
invention., T,he, protective skin 12 preferably comprises a
single faced,corrugated paper board structure having a
corrugated paper board medium 14 and an outer liner 16
adhered to the crest portio~s of the corrugated medium
wlth a suitable adhesi~e, such as for example a wet
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strength adhesive. A thin layer of reflecting material 20,
which may for example comprise a thin sheet of aluminum
foil, is in turn adhesively secured to the outer surface
of the liner 16, i.e., the surface opposite to the surface
adhered to the crest portions of the corrugated medium 14.,
The composite protective skin 12 may be provided with a
plurality of pre-perf~rations 22 which pass through the'
corrugated medium 14, the paper board liner 16 and the
thin layer of reflecting material 20, for a purpose to be
explained more fully hereinbelow.
There is shown in Figure 2 a heat insulating panel 10
in accordance with the present invention which is
particularly userul as a roofing panel for construction of
a built-up roof. The panel '10 comprises upper and lower
protective skins 12, 13 having a core 24 of foam material
therebetween such as for example phenolic foam material
, which is dimensionally moisture sensitive. The upper
protective skin 12 comprises a skin s'uch as shown in
Figure 1 having a thin layer of reflecting material 20
thereon, whereas the lower protective,skin 13 is of a
similar construction to the upper skin 12 with the
exception that no layer of reflecting material need be
25- provided. Thus, it will, be noted in Figure 2 that the
thin layer of reflecting material 20 need only be ,
provided on one of the outer surfaces of the formed
heat insulating roofing panel 10, i.e., on the surface
of the corrugated paper board facing away from the
corrugated medium 14 and also away from the core'24
of the phenolic'oam material therebetween.
The upper and lower protective skins 12, 13 both
preferably 'c,omprise single faced corrugated skins which
provide for a good adhesion between skins 12, 13
and the phenolic foam material 24 therebetween as a result
of the reduction of the amount of volatile materials
accumulated between the skins 12, 13 during the manu-
facturing process and of the foamable resin compound
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passing through the,plurality of pre-perforatio,ns 22
~rovided therein. ~he heat insulating bo~rd or panel 10
panel 10 may also be provided with a ~-
plurality of post-perforations 26 which provide for an
increased bond between the core 24 oP the foam, the
protective skins 12, 13 and the roof supporting structure'
30 on one side of the heat insulating roofing panel 10
and the finishing roofing membrane 32 on the other side
thereof by means of the roofing adhesive 34 and the
roofing bitumen 26 which penetrates through the post-
perforation holes during the process of forming the
resulting roofing structure 40 (see Figure 3). In,.this
, regard, the roofing material ~either the roofing adhesive
34 for securing the panels 10 to the roof supporting
structure 30 or the bitumen 36 applied over the upper
surface of the roofing panels 10 during the construction
of the roof 40) will seep through the post-perforations
26 and form plugs 28 which provide a firm water
resistant bond between the roofing materia.ls and ~he
heat insulating roofing panel'or board 10.
~ ore particularly, during the construction of
a built-~up roof;:40, a plurality of the heat insulating
roofing panels 10 such as shown in Figure 2 are placed on
a suitabLe roof,supporting structure 30,.which may for
example compri'se a corruqated sheet steel support, the
crests or pe'aks of which serve to sup'port the ro~fing
panels 10. This is shown in cross-section in Figure 3.
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In this placement of the roofing panels 10 on the
, corrugated support s'tructure 30, the panels 10 are ,
arranged in side by side relationship to cover the entire
upper surface of the corrugated support structure 30.
Each of the panels 10 is arranged so that the thin layer
of reflecting material 20 provided on the outer surface
of one of the sides of the panels 10 faces away from
the roof supporting structure 30, i.e., to face upwardly
as shown in ~igure 3. Thus, it will be appreciated that
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the thin layer 20 of reflecting material will be exposed
to any sun radiation which is present during this phase
of the construction of the roof. ' -,
lS Each of the roofing panels 10 may be suitably secured
to the corrugated roof supporting structure 30 with any
suitable adhesive 34, such as for example by roofing
adhesive which may penetrate the bottom protective skin
13 through the post-perforations 26. This will form the
' 20 aforementioned plugs 28 in the lower side of the panel 10.
After the panels 10 have been laid up on the roof
supporting structure 30 with the layers 20 of reflecting
material facing the sun, one or more layers of roofing'
materiai are then applied over the upper surfaces of the
heat insulating panels 10. These roofing materials may
comprise bitumino,us roofing materials such as alternating
layers of asphalt 36, and asphalt saturated roofing felts
38, with the system then being gravelled over to complete
the finished roof structure 40. In the embodiment shown
30 'in Figure 3, four layers each of asphalt 36 and ,38
are shown.- Ho,~ever, if desired, fewer or more layers
could be provided.
As'noted in the Background of the Invention section,
prior art he'at insulating roofing panels constructed
of ,foam material have experienced problems in curling or
warpage. This is believed in part to be due to the fact
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that the foam material has a tende~cy to absorb and retain
moisture. For example, the foam materials may have a
tendency to absorb approximately 10% moisture by weight
. 5 when in an environ~ent at 50% relative humidity at
room temperature. During the.construction process in the
prior art in which the panels are initially placed on
the roof support, and exposed and unprotected from the
sun radiation, the heat from the sun radiation on the
upper surface of the panels can cause a high temperature
differential across the opposite surfaces which can
have the effect of driving the moisture in the foam
material away from the hot side towards the cold..side,.
and/or uneven evaporation of the moisture therewithin.
For example, up to a 55 F differential (140 F at the
.. . upper surface and 95 F at the lower surface) has . , .
been experienced with the prior art heat insulating
roofing panels. The high temperature differential across
. the prior art panels (i.e., panels in which ~o reflecting
material is provided on the outer surface of the panel) is
thus believed to have caused the curling or-warpage of the
panels. For example, curling of up to one inch.in a two
inch thick roofing panel has been experienced.
.. However, in accordance with the present invention in
which the roofing panels 10 are provided with a thin
layer 20 of reflecting material on the outer upper surface
thereof, the effects of curling are greatly reduced.
It is believed that this is the result of the fact that
the thin layer 20 of xeflecting material serves to
reflect and dir~ct the sun radiation away from the upper
surface of the heating panel 10 before the application
of the roo.fing material 36, 38 and thereby results in a
decrease in;the temperature differential across the
thickness of the panels 10. Thus, in accordance with the
preferred em~odiment of the present invention in which a
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20 of aluminum foil is adhesively secured to the outer
upper surface of the roofing panel 10, the thickness
being below .001 inches, for example on the order of
. .00035 inches, the amount of curling experienced in a
two inch thick roofing panel 10 has been reduced to below
3/8 inch and in most instances to ~ inch or less.
. It should be appreciated that although the Present
invention has been mainly described with reference to
heat insulatiag panels for built-up roofs, the principles
employed could also be used for. heat insulating panels
for building constructions in general. For example,
insu~ated foam sheating panels nailed or secured..to the
outside side walls of buildings, which have also
experienced some problems of curling in the past, could
be provided with a thin layer of reflecting material on
the outer surface to minimize curling or warpage of the
panels prior to the application of shingles or siding
thereover.
- - Preferably, the layer 20 of reflecting material is
adhered to the liner 16 of corrugated paper board 12 or
other material utilized as the protective skin of the .
roofing panel 10 by means of a high wet strength adhesive.
In this regard, by wet strength adhesive it should be
understood that any adhesive which maintains the bond
between the liner 16 and the layer 20 of reflecting
material over a long period bf.time of water immersion,
can be employed. For example, such suitable wet strength
adhesive may comprise thermosetting polyvinyl acetate
based adhesive as well as neoprene adhesives. The same
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types of adnesive may also be utilized in adhesively
securing the liner 16 to.the corrugated medium 14.
Further~ the thin layer 20 of reflecting material, in
accordance with the present invention, is preferably
adhesively secured to the corrugated paper board 12 or
other medium prior to the use of the paper board medium 12
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~ in the manufacturing of the heating panels 10. In other
.v words t the thin layer 20 of reflecting material' is
preferably initially laminated to the corrugated paper
board 12 in the preferred embodiment to form a protective
skin 12 prior to the manufacture of the heating panel 10
and the use of the protective s~in 12 in such manu-
facturing process. Xn this regard, desirably th'e manu-
facture of the panels 10 will be in accordance with a
continuous method similar to that described for example in
U.S. Patent No. 3,821,337 to Bunclark, issued January 28,
1974. For example, twenty-four inch ~ide
panels can be manufactured which are then cut into four
foot lengths. In this regard, U.S.'Patent No. 3,821,337
not only describes a continuous process' for'the manu-
facture of heat insulating panels but also describes
resins which may be employed therein.
However, it should also be appreciated that the
present invention could be employed with other types of
foam materials which are dimensionally thermo - or hydro -
'sensitive, such as for example some poly-styrene or
urethane foams, in order to minimize curling or warping
of the heat insulating panels.
~he density of the resulting core 24 of open celled
phenolic foam material is generally in the range of about
1.5 to 6.~ lb./ft3 and preferably about 2 to 3.5 lb./ft3.
The preparation o the resin and its foaming are well
known in the chemical art as well as tne roofing art and
needs no furth~e;~ elaboration herein. Examples of such
materiaIs can be'found in U.S. Patent Nos. 3,741,920,
3,726,708, i,694,387, 3,779;956, 3,877,967, and 3,953,645.
Although~va~ious types of media may be used for'the
protective skins 12, 13 tor for providing a corrugated
protective skin), it is preferred that single faced
35. corrugated paper board be used, since such material
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- ~ is generally less costly in comparison to other suitable
materials. Such suitable single faced corrugated paper
board may for example include a liner and medium of'
kraft, semi-chemical or other similar paper material.
Typical weights for such paper board amy range from about
26 lb./1000 ft to about 42 lb./1000 ft2; however, it
should be understood that other weights ~or the paper
board could be utilized. ': -
' Also, although in accGrdance with the preferrea
embodiment of the present invention both pre-perforations
22 and post-perforations 26 are provided in the protectiye
skins 12, 13,it will be appreciated that use of SUCh perfora-
tions 22, 26 is not necessary, as a wide variety of types and
configurations of protective skins 12, 13 could be used
in combina'tion with a thin layer 20 of highly reflective
material adhesively secured to the o~ter surface thereof.
While in accordance with the preferred embodiment,
the layer of reflecting material preferably comprises a
thin layer 20 of aluminum foil, it should also be '
appreciated that other types of highly reflective
materials could also be utilized which would serve to
re~lect and direct sun radiation away from the upper
surface of the panel when same is'supported on a building'
structure. Such highly reflective material should
- preferably have an emissivity o~ less than 0.30, and
more preferably less than 0.10. Aluminum foil has an
emissi~ity of a~proximately 0.05. Another suitable
material may for example comprise a very thin layer of
gold. Furthermore, although in the preferred embodiment'
the layer'o~ aluminum has a thickness of less than
0.001 inches.and preferably on the order of .00035 inches,
other thicknesses may of course be used. The main
consideration in this regard may be the cost o~ such
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materials. Thus, it will be appreciated that the
thinner the layer 20, the less expensive the cost.for
the res~lting panel 10. The major requirement on the
. thickness of the highly reflective material is whether
5 . the material may be adhesively secured to the protective
skin medium.
While the preferred embodiment of the present
. invention has been shown and described, it will be
Lnderstood that such is merely illustrative and that
changes may be made without departing from the scope of
the invention as claimed.
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