EP0039158A2

EP0039158A2 - Insulating foam building panel and method of construction utilizing such panels

Info

Publication number: EP0039158A2
Application number: EP81301563A
Authority: EP
Inventors: Eric Ptru Stern; Solomon Martin Vines
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1980-04-25
Filing date: 1981-04-09
Publication date: 1981-11-04
Also published as: EP0039158A3; DK152392B; NO811393L; DK152392C; DK180181A; CA1146331A

Abstract

A heat insulating panel for use in construction of building structures such as a built-up roof. The heat insulating panel comprises first and second oppositely disposed surfaces with a core therebetween comprised of phenolic foam material. The first surface of the panel includes a thin layer of reflecting material over substantially the entire surface thereof to reduce the heat conveyed to the core due to sun radiation when the layer of reflecting material on the panel is exposed to sun radiation during construction of the building structure. This reduction in the heat conveyed to the core reduces cαrl- ing or warping of the panel, before application of finishing materials, such as bituminous roofing material, over the panels. There is also disclosed a method of constructing a building structure with such heat insulating panels.

Description

BACKGROUND OF THE INVENTION

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 structures, 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 purposes in building structures such as exterior or partition 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. One example of such use of phenolic foam material employed in a roofing structure is disclosed in U.S. Patent 4227356. Other low thermal conductivity foam materials may 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/ft³ so as to have sufficient strength to support persons and their equipment.
Typically, in such construction applications, the foam material is sandwiched between a pair of protective skins, such as for example paper or paper composites. The protective skins serve as a convenient means of making the heat insulating panels, as well as to protect and maintain the integrity of the sandwiched foam material.
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 particularly, 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. However, 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, curling 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 components 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 finishing materials thereover, and as such overcomes some of the above discussed and other disadvantages of the prior art. More particularly, in accordance with the present invention, the improved heat insulating panel comprises first and second oppositely disposed surfaces having a core therebetween comprised of heat insulating foam material. One of the oppositely disposed surfaces includes a thin layer of reflecting material over substantially the entire surface thereof to reduce the heat conveyed to the core due to sun radiation when the insulating panel is exposed to sun radiation duringthe 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 foam materials have a tendency to retain moisture which, given enough time, reaches equilibrium with the atmospheric vapor partial pressure. For 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 drive the moisture in the panels from the hot side of the panel to the relatively cool side of the panel, thereby causing shrinkage 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 aforementioned curling problem experienced in the prior art.
However, with the present invention, during the construction of the building structure, the heat insulating 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 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. For 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 entire 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 serves 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 over the supported panels to thereby substantially cover the reflecting material. In this way, the problem of warping or 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 reflecting 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

Referring now to the drawings wherein like reference characters represent 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. The 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 portions of the corrugated medium with a suitable adhesive, such as for example a wet 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-perforations 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 useful 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 such 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 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 foam material therebetween.
The upper and lower protective skins 12, 13 both preferably comprise 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 manufacturing process and of the foamable resin compound passing through the plurality of pre-perforations 22 provided therein. This feature is more fully disclosed in U.S. Patent 4227356, which is hereby incorporated by reference, and which discloses that a good bond strength between the foam core 24 and the corrugated protective skins 12, 13 is provided.
Also, as more fully discussed in the aforementioned Patent 4227356, the heat insulating board or panel 10 may be provided with a plurality of post-perforations 26 which provide for an increased bond between the core 24 of 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 materials and the heat insulating roofing panel or board 10.
More 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 comprise a corrugated sheet steel support, the crests or peaks of which serve to support the roofing panels 10. This is shown in cross-section in Figure 3. In this placement of the roofing panels 10 on the corrugated support structure 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 Figure 3. Thus, it will be appreciated that 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.
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 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 material are then applied over the upper surfaces of the heat insulating panels 10. These roofing materials may comprise bituminous 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 in Figure 3, four layers each of asphalt 36 and 38 are shown. However, if desired, fewer or more layers could be provided.
As noted in the Background of the Invention section, prior art heat 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 that the foam material has a tendency to absorb and retain moisture. For example, the foam materials may have a tendency to absorb approximately 10% moisture by weight when in an environment 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 no 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 reflecting material serves to reflect and direct the sun radiation away from the upper surface of the heating panel 10 before the application of the roofing 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 embodiment of the present invention in which a 20 of aluminum foil is adhesively secured to the outer upper surface of the roofing panel 10, the thickness being below .001 inches, for ex- , ample 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 1/4 inch or less.
It should be appreciated that although the present invention has been mainly described with reference to heat insulating panels for built-up roofs, the principles employed could also be used for heat insulating panels for building constructions in general. For example, insulated foam sheathing 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 of 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 types of adhesive 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 in the manufacturing of the heating panels 10. In other words, 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 skin 12 in such manufacturing process. In this regard, desirably the manufacture 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, which reference is herebyincorpor- ated by reference in its entirety. For example, twenty- four inch wide 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 manufacture 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.
The density of the resulting core 24 of open celled phenolic foam material is generally in the range of about 1.5 to 6.0 lb./ft3 and preferably about 2 to 3.5 lb./ft³. The preparation of the resin and its foaming are well known in the chemical art as well as the roofing art and needs no further elaboration herein. Examples of such materials can be found in U.S. Patent Nos. 3,741,920, 3,726,708, 3,694,387, 3,779,956, 3,877,967, and 3,953,645.
Although various types of media may be used for the protective skins 12, 13 (or for providing a corrugated protective skin), it is preferred that single faced corrugated paper board be used, since such material 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 may range from about 26 lb./l000 ft ² to about 42 lb./1000 ft ; however, it should be understood that other weights for the paper board could be utilized.
Also, although in accordance with the preferred embodiment of the present invention both pre-perforations 22 and post-perforations 26 are provided in the protective skins 12, 13, (in accordance with the principles of the aforementioned Patent 4,227,356), it will be appreciated that use of such perforations 22, 26 is not necessary, as a wide variety of types and configurations of protective skins 12, 13 could be used in combination with a thin layer 20 of highly reflective material adhesively secured to the outer 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 reflect 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 of less than 0.30, and more preferably less than 0.10. Aluminum foil has an emissivity of approximately 0.05. Another suitable material may for example comprise a very thin layer of gold. Furthermore, although in the preferred embodiment the layer of 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. Themain consideration in this regard may be the cost of such materials. Thus, it will be appreciated that the thinner the layer 20, the less expensive the cost for the resulting panel 10. The major requirement on the thickness of the highly reflective material is whether 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 understood that such is merely illustrative and that changes may be made without departing from the scope of the invention as claimed.

Claims

1. A heat insulating panel for building structures comprising:

first and second oppositely disposed surfaces;

a core comprised of foam material between said first and second surfaces; and characterized by

said first surface including a thin layer of reflecting material over substantially the entire surface thereof to reduce the heat conveyed to the core due to sun radiation when said layer of reflecting material on said first surface of said panel is exposed to sun radiation during construction of a building structure with said panels.

2. A heat insulating panel according to Claim 1 characterized in that said reflecting material comprises a material having an emissivity of less than 0.30.

3. A heat insulating panel according to Claim 2 characterized in that said reflecting material has an emissivity of less than 0.10.

4. A heat insulatng panel according to Claim 3 characterized in that said thin layer of reflecting - material comprises a thin layer of aluminum foil.

5. A heat insulating panel according to Claim 4 wherein said thin layer of aluminum foil has a thickness of less than 0.001 inches.

6. A heat insulating panel according to Claims 1-5 characterized in that it includes a pair of protective skins between which said core of foam material is sandwiched, each of said skins having an inner surface adhered to opposite sides of said core, and an outer surface, said outer surface of one of said protective skins defining said second surface of said heat insulating panel and said thin layer of reflecting material being adhesively secured to said outer surface of the other of said pair of protective skins.

7. A heat insulating panel according to Claim 6 characterized in that said pair of protective skins each comprise single faced corrugated paper board, the corrugations of each of said single faced corrugated paper boards defining said inner surface adhered to said core.

8. A heat insulating panel of claim 6 wherein said pair of protective skins each comprise a corrugated medium having one side adhered to said core, and a liner adhered to the crests of the opposite side of said corrugated medium.

9. A heat insulating panel according to Claims 1-8 characterized in that said thin layer of reflecting material is adhesively secured to one of said protective skins with a high wet strength adhesive.

10. A heat insulating panel according to Claim 9 characterized in that said high wet strength adhesive comprises a neoprene adhesive.

11. A heat insulating panel according to Claims 1-10 characterized in that said core of foam material comprises phenolic foam material.

12. A heat insulating panel according to Claim 11 characterized in that said core of phenolic foam material includes open celled phenolic foam material.

13. A method of constructing a heat insulating building structure comprising the steps of:

providing a plurality of heat insulating panels;

attaching said plurality of heat insulating panels to a building support structure; and

applying at least one layer of finishing material over said supporting panels to thereby substantially cover the reflecting material;

characterized in that as the panels there are employed heat insulating panels according to Claims 1-12 which are attached to the support structure in such a way that the layer of reflecting material on said first surface is exposed to sun radiation which may be present.

14. A method of constructing a heat insulating building structure according to Claim 13 in which said building structure comprises a built-up roof, characterized in that said heat insulating panels comprise heat insulating roofing panels, and that said step of attaching comprises laying said heat insulating roofing panels on a roof support structure so that said second surfaces of said panels are adjacent to said roof support structure.

15. A method of constructing a heat insulating roofing structure according to Claims 13 or 14 characterized in that said step of applying at least one layer of finishing material comprises applying at least one layer of roofing material over said layers of reflective material.

16. A method of constructing a heat insulating roofing structure according to Claim 15 characterized in that said step of applying at least one layer of finishing material comprises applying at least one layer of asphalt over said thin layers.

17. A method of constructing a heat insulating roofing structure according to Claims 13-16 characterized in that said step of applying comprises applying several layers of roofing material over said layer of reflective material on each of said roofing panels.