Rainscreen wall panel

Abstract

A rainscreen wall panel is provided having an air gap between an outer facing sheet and an insulating layer, the insulating layer being backed by a reinforced concrete supporting layer. The panel is constructed in a mold, spacers being used to maintain the air gap until the concrete has cured. The presence of the air gap enables the facing layer thermally to expand or contract or to bow under pressure independently of the concrete supporting layer. The air gap communicates with the ambient air, thereby ensuring that, under steady state conditions, the pressure in the air gap is substantially equal to the pressure of the ambient air. As a result of this pressure equalization, the facing sheet need only be designed to withstand those forces which might be created during unsteady state conditions, and during steady state conditions moisture will not seep through the facing sheet.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a rainscreen wall panel which can be mounted on a building as part of a complete wall, and to a method of constructing the same.

2. Description of the Prior Art

It is known to have wall panels which can be mounted on buildings as part of a complete wall. However, in many previous panels the facing sheet has to be designed to withstand the total force of external wind suction or pressure, or different coefficients of thermal expansion of the outer facing sheet and the supporting layer may cause relative movement between the facing sheet and the supporting layer, sometimes causing the panel to crack, or moisture may seep through the facing sheet, accompanied by subsequent freezing, causing the panel to crack.

SUMMARY OF THE INVENTION

This invention relates to a rainscreen wall panel having an air gap between a rigid outer facing sheet and a rigid layer of thermal insulation, the insulating layer being backed by a supporting layer of reinforced concrete capable of withstanding forces to which the panel may be subjected. The facing sheet is held apart from the insulating layer by anchoring means which extend from the concrete slab to the facing sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, which illustrate an embodiment of the invention:

FIG. 1 is a side front view of a panel having a facing sheet made up of eight marble slabs;

FIG. 2 is a sectional view along the line 2--2 of FIG. 1 through the panel and parts of window frames above and below the panel;

FIG. 3 is an enlarged sectional view of part of the panel taken along the line 3--3 of FIG. 1;

FIG. 4 is a rear view of the panel on a smaller scale than FIG. 1, taken along the line 4--4 of FIG. 2 and showing columns from which the panel is supported; and

FIG. 5 is a perspective view of forms being used during the construction of the panel.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings in greater detail, in FIG. 4 two vertical columns 2 support a steel spandrel beam 4 horizontally between them. The beam 4 has flanged upper and lower edges 6 and can be welded to the columns 2. The vertical columns 2 and the steel spandrel beam 4 are part of a building (not shown). The beam 4 is conventional in building construction and need not be further discussed. A panel 8 is mounted on the beam 4.

Referring to FIG. 2, the panel 8 is mounted at the outer side 10 of the beam 4. The means for mounting the panel 8 will be discussed in more detail below. The panel 8 is constructed with flanged upper and lower edges 16, which extend rearwardly from the panel and constitute means whereby the panel can be attached on a building structure. After the panel 8 is mounted on the beam 4, an inner surface 12 of the beam 4 and the flanges 6 are coated with a low insulating sprayed fire-proofing material 14, for example, an asbestos-based material. The fire-proofing material 14 contacts the flanges 16 of the panel 8, leaving an air space 18 between an inner surface 20 of the panel 8 and the outer surface 10 of the beam 4. The ends of the flanges 16 are cut away at 17 to allow for the columns 2 (see FIG. 4).

The panel 8 includes precast reinforced concrete supporting layer 22 which is bonded to a rigid layer of thermal insulation 24. An air gap 26 is provided between the insulating layer 24 and a rigid outer facing sheet 28. The facing sheet 28 is supported by anchors 30, 32 so as to maintain the air gap 26.

The facing sheet 28 may be a single sheet or a plurality of sheets placed edge to edge depending on the desired size of the panel and the type of material used as the facing sheet. Numerous types of materials are suitable as facing material. Examples of facing material are marble, granite, concrete, slate, stone, glass and stainless steel. The type of anchors used will vary depending upon the type of facing material used.

In the particular embodiment illustrated, marble is the facing material and the facing sheet 28 is made up of eight rectangular marble facing slabs 34 arranged edge to edge in two horizontal rows. Between the facing slabs 34 are spaces 36 approximately 3/8 inch wide as shown in FIG. 1. The spaces 36 between the slabs 34 are sealed with a suitable caulking material 38, for example, a polysulfide sealant, to prevent ingress of moisture through the spaces 36. Marble-to-marble joints between the panel illustrated and adjacent panels (not shown) are also approximately 3/8 inch in width and sealed with a suitable caulking material. In addition, spaces between the panel illustrated and adjacent panels (not shown), along the edges of the insulating layer 24 and the concrete supporting layer 22, are sealed with a suitable caulking material in order to prevent moisture from passing through said spaces and also to seal off the air space 18 between the inner surfaces 20 of the panels and the spandrel beam 4. The sealed air space 18 acts as an insulator. As shown in FIG. 2, adjacent to the top and bottom of the panel 8 are window frames 40, 42 respectively. Any gap between the top frame 40 and the facing sheet 28 is sealed with a suitable caulking material at 44. However, the upper surface 48 of the bottom frame 42 is spaced below the air gap 26, leaving an unsealed opening 46 extending the width of the gap 26. The opening 46 forms a passageway connecting the air gap 26 to the ambient air. The opening 46 ensures that, under steady state conditions, the pressure of the air in the air gap 26 will be substantially equal to the pressure of the ambient air. Furthermore, the upper surface 48 of the bottom frame 42 is sloped downwardly and outwardly from the insulating layer 24 of the panel 8 so that water collected or formed in the air gap 26 can drain away through the opening 46.

Each marble slab 34 of the panel 8 is fixed to the concrete slab 22, in a plane parallel to the slab 22, by five anchors 30, 32. Four of these anchors 30 are restraining pins, each having a threaded end 50 and a headed end 52. The threaded end 50 of each pin 30 is embedded in the concrete slab 22. From the slab 22, each pin 30 extends through the insulating layer 24 and into a dovetail hole 54 in the inner surface 56 of the marble slabs 34. Each hole 54 contains a filler 58, such as epoxy resin, which prevents the facing slab 34 from moving relative to the pins 30. The pins 30 are designed to withstand any force on the facing slab 34 normal to the panel 8. The load or weight of each marble slab 34 is carried principally by the fifth anchor which is a straight steel rod 32. The steel rod 32 is embedded in a concrete projection 60 of the concrete slab 22, the projection 60 extending through a hole 62 in the insulating layer 24. From the projection 60, the rod 32 extends through a pad 64 of resilient material, for example, polystyrene or rubber, and into a hole 66 in the inner surface 56 of the marble slab 34. The inner portion of the hole 66 is filled with a buffer 68, such as neoprene rubber, to reduce the shock when the slab 34 is forced against the rod 32, for example, by a gust of wind. The resilient pad 64 separates the concrete projection 60 of the concrete slab 22 from the marble slab 34 and acts as a spacer defining the thickness of the air gap 26. The four pins 30 are located approximately 1/5 of the length of the marble slab 34 from an edge thereof and approximately 1/5 of width of the slab 34 from another edge thereof. These points are points of minimum stress if the marble slabs are bowed by external forces. The rod 32 is located in the centre of mass of the marble slab 34.

The panel is supported from the beam 4 near six points 70-75, indicated in FIG. 4. The actual means of support are well known to those skilled in the art and need not be described in detail. Suitable examples are shown in 1971 Form No. 30791 published by the Mo-Sai Institute, Inc. and entitled "Precast Concrete with Exposed Aggregate". The present address of the Mo-Sai Institute is c/o David W. Evans and Associates, 110 Social Hall Avenue, Salt Lake City, Utah, U.S.A. 84111. At the points 70, 72, near its upper corners 78, the panel 8 is restrained vertically as well as horizontally normal to the panel. At the point 71, near the centre of the upper edge 80, the panel 8 is restrained horizontally in all directions. Near the lower edge 82, at the points 73, 75 near the corners 83, and at the point 74 near the centre of the lower edge 82, the panel 8 is restrained horizontally normal to the panel. Other types of restraints can be employed so long as they permit differential movements of the panel and beam due to variations in temperature, concrete shrinkage and building deflections.

As shown in FIG. 5, the panel 8 is constructed using a mold 84 which can be made of wood, steel, precast concrete or other suitable material. The panel 8 is constructed by first placing the marble slabs 34 edge to edge (with approximately 3/8 inch spaces 36 between them) face down in the mold 84. The pins 30 and the rod 32 can be affixed to each slab 34 either before or after the slabs are placed in the mold 84. Next, spacers 86, which can be rubber strips, are laid crosswise on the top surfaces 56 of the marble slabs 34, the thickness of the spacers 86 defining the air gap 26. The spacers 86 extend through slots 88 in the sides 90 of the mold 84. A resilient pad 64 is placed around the rod 32 of each slab 34. Then, the insulating layer 24 is laid on the spacers 86 with the anchors 30, 32 extending through the insulating layer. A grid of reinforcing steel (not shown) is placed over the upper surface 92 of the insulating layer 24. The grid is designed in the usual way to reinforce the concrete. Concrete is then poured onto the upper surface 92 of the insulating layer 24 and around the reinforcing grid to form the layer 22. The resilient pad 64 of each slab 34 separates the concrete from the marble slabs 34 and prevents the concrete from running into the air gap 26. The concrete flows into each hole 62 in the insulating layer 24, thus forming the projection 60 in which the rod 32 of each slab 34 is embedded. The number of spacers 86 required depends on the size of the panel, the strength of the insulating layer 24 and the weight of the concrete slab 22. The concrete, in setting, adheres or binds itself to the insulating layer 24. After the concrete is set, the panel is removed from the mold 84. The spacers 88 can be removed by pulling them longitudinally either before or after the panel 8 is removed from the mold, leaving the air gap 26 between the marble slabs 34 and the insulating layer 24.

As stated above, due to the fact that the air gap 26 communicates through opening 46 with the ambient air, under steady state conditions, the pressure of the air in the air gap is substantially equal to the pressure of the ambient air. Therefore, since the air gap is located between the facing sheet and the insulating layer, under steady state conditions the pressure on either side of the facing sheet will be the same. It follows that under steady state conditions there will not be any resultant air pressure force acting on the facing sheet normal to the facing sheet and that all forces normal to the panel will be taken by the reinforced concrete supporting layer. Thus, the facing sheet need only be designed to withstand forces during unsteady state conditions, which occur due to a sudden change in wind suction or wind pressure. Another advantage of the air gap is that, under steady state conditions, moisture on the outer surface of the facing sheet or on joints between the facing sheets will not seep through the facing sheets because there is no pressure differential across the facing sheets or joints. Thus, under steady state conditions, rain falling against the outer surface of a facing sheet will not penetrate the facing sheet because the pressure on both sides of the facing sheet is the same. Thus, the facing sheet in combination with the air gap acts as a rainscreen. Any moisture that collects in the air gap can form droplets that will drain out of the air gap through the opening 46 at the bottom. The air gap must be sufficiently wide that water will drain away rather than form a film across the air gap. If the gap were so narrow that water would form a film across it, a film of water might block the air gap and thereby defeat its purpose with respect to pressure equalization. Other advantages of the panel of this invention are that the facing sheet can thermally expand and contract, to some degree, independently of the supporting layer. Also, the facing layer can bow independently of the supporting layer.

Preferably, the air gap of the present invention has a thickness between about 1/4 inch to 2 inches. The thermal insulation or the insulating layer 24 preferably has a thickness between about 1/2 inch to 3 inches. The thickness of the insulating layer depends on the thermal conductivity of the particular type of insulation used, on the insulation requirements of the particular building where the panel is to be used, on the rigidity or strength of the insulation used and on the thickness of the precast concrete supporting layer. The insulation used in the embodiment illustrated is expanded polystyrene, the marble slabs having a thickness between about 3/4 inches to 11/2 inches. Whenever marble is used as a facing sheet according to the present invention, it preferably has a thickness between about 3/4 inches to 3 inches.

Various types of anchors can be used to support the facing sheet in accordance with the invention. The panel can be attached to virtually any building structure having sufficient strength to support it. Modifications within the scope of the attached claims will readily occur to those skilled in the art.

Claims

The embodiments of the invention in which exclusive property or privilege is claimed are defined as follows:

1. A prefabricated rainscreen wall panel comprising a precast reinforced concrete slab capable of withstanding forces to which the panel may be subjected, a rigid layer of thermal insulation over the outer surface of the concrete slab and fixed thereto, a rigid, decorative outer facing sheet extending over the layer of insulation, spaced apart anchors fixing the facing sheet to the concrete slab, a gap for circulation of air separating the facing sheet and the insulation layer, the reinforced concrete slab having a projection through the insulation layer, one of said anchors being embedded in said projection and in the facing sheet, the projection being separated from the facing sheet by a resilient pad, and a passageway through which the gap communicates with the atmosphere, the panel being in the form of a transportable unit and having means on the rear surface of the slab whereby the panel can be attached on a building structure.

2. A panel as claimed in claim 1, wherein the resilient pad constitutes a spacer defining the thickness of the air gap.