Glazing forming a spandrel panel for a building façade, capable of limiting ground-level heating caused by the reflection of solar radiation by the façade

Abstract

The invention relates to glazing comprising at least one mineral glass sheet (1) coated, on at least a portion of its surface, with a transparent enamel (2) textured according to surface patterns forming angles of between 5 and 90° with the main surface of the mineral glass sheet (1), the glazing comprising a layer of opaque enamel (3), the transparent enamel (2) being in an intermediate position between the mineral glass sheet (1) and the layer of opaque enamel (3); a method of manufacturing the glazing; and its use for limiting the heating of an urban environment.

Description

[0001] Description

[0002] Title: Glazing Constituting a Building Façade Span Capable of Limiting Ground Heat Gain Due to Solar Radiation Reflection from the Façade. The invention relates to the heat gain observed in urban areas with high concentrations of tall buildings, such as towers and business districts. This heat gain is known to be linked to the reflection of solar radiation from large glazed surfaces in these areas towards the ground. This phenomenon is known as "Urban Heat Island."

[0003] The inventors sought an effective way to significantly reduce the reflection of solar radiation towards the ground. More specifically, they aimed to make the solar radiation reflected by building facades, particularly tall buildings in densely built-up areas, back towards the sky rather than the ground. This allowed them to substantially reduce the temperature rise during sunny periods, especially during the intense summer heat, at sidewalk level near buildings with large glazed surfaces, such as skyscrapers in business districts or densely populated urban areas.

[0004] To this end, the invention relates to a glazing unit comprising at least one sheet of mineral glass coated, on at least a portion of its surface, with a transparent enamel textured with surface patterns forming angles of between 5 and 90° with the main surface of the mineral glass sheet. The glazing unit comprises a layer of opaque enamel, the transparent enamel being in an intermediate position between the mineral glass sheet and the opaque enamel layer. The glazing unit of the invention is opaque and readily forms a colored spandrel panel in black, white, or any other color. "Spandrel panel" refers to an opaque lower portion of the exterior wall of a building floor; thus, a spandrel panel is commonly extended upwards by a visible portion of the floor, consisting of a window or similar feature. The spandrel panel formed by glazing of the invention is capable of providing an aesthetically pleasing effect of continuity with the upper visible portion of the floor.The use of opaque glass panels as spandrel panels on facades to conceal structural elements of buildings, particularly curtain walls, is already known. A glazing unit according to the invention, positioned with its textured transparent enamel facing away from the sun—that is, towards the interior of the building—has the property of reflecting a portion of the incident solar radiation upwards. We will see later that it is effective in mitigating the "Urban Heat Island" effect.

[0005] In a particularly advantageous embodiment, the transparent enamel is directly coated with a solar control coating between the transparent enamel and the opaque enamel layer. The solar control coating reflects a fraction of the solar radiation, thereby reducing the induced heating inside the building and, consequently, the energy consumption required for cooling by air conditioning or equivalent means. Furthermore, in combination with the textured transparent enamel and the opaque enamel layer, it provides an additional means of reflecting solar radiation back into the sky. The solar control coating is preferably a stack of thin layers comprising at least one functional layer that reflects solar radiation, in particular at least one layer of silver.Each functional layer or layers is preferably surrounded by one or more dielectric layers, for example made of oxide, nitride or oxynitride of silicon, aluminum, zinc, tin or zirconium.

[0006] In a preferred embodiment, the main glazing surface is divided into a first part with an opaque enamel coating and a second part without an opaque enamel coating. The first part forms a spandrel panel (opaque), and the second part a glazing or vision glass. In the glazing installation position, the facade of a building floor can thus consist of a lower spandrel panel and an upper vision glass panel delineated by a horizontal line. The textured transparent enamel on the vision glass panel is not visible, but it also reflects solar radiation upwards, thus contributing, like the spandrel panel, to limiting ground-level heating caused by solar radiation reflected from the facade. In this embodiment, the spandrel panel and the vision glass present a visual continuity.

[0007] According to a first embodiment of the invention, the glazing is monolithic, and the opaque enamel layer directly covers the transparent enamel, or the solar control coating when present. According to a second embodiment of the invention, the glazing is laminated, an intermediate adhesive layer directly covers the transparent enamel, or the solar control coating when present, a second sheet of mineral glass directly covers the intermediate adhesive layer, and the opaque enamel layer directly covers the second sheet of mineral glass.

[0008] According to a third embodiment of the invention, the glazing is double, consisting of a laminated glazing and a monolithic glazing held at a constant distance from each other by an interlayer so as to form a layer of air or gas, and in the laminated glazing, an adhesive interlayer layer directly covers the transparent enamel, or the solar control coating when present, a second sheet of mineral glass directly covers the adhesive interlayer layer, the second sheet of mineral glass being in contact with the layer of air or gas, and the monolithic glazing comprises a third sheet of mineral glass, the face of which opposite the layer of air or gas is coated with the opaque enamel layer.

[0009] Preferably, the transparent enamel and the opaque enamel layer are zinc borosilicate frits. After firing the enamel, such frits form a mineral binder with strong adhesion to the glass sheet. The thickness of the enamel layers after firing is preferably between 10 and 30 µm.

[0010] Preferably, the opaque enamel layer contains at least one pigment such as chromium oxide Cr2O3, titanium dioxide TiC, or copper oxide CuO. The transparent enamel is pigment-free.

[0011] Preferably, transparent enamel contains mineral particles. This optimizes reflection. Examples include metallic particles.

[0012] Preferably, the transparent enamel is textured with surface patterns forming angles with the main surface of the mineral glass sheet between 10° and 90°, particularly between 10° and 80°, or even between 10° and 70°, or between 10° and 60°. The angle can be determined microscopically by measuring the angle formed between the slope of the pattern and the surface of the glass sheet. The surface patterns may be identical or different. They can be any shape. For example, they may be dots, squares, triangles, etc. The largest dimension of the patterns is preferably between 0.1 and 2.0 mm, particularly between 0.2 and 1.0 mm. The pattern coverage, that is, the proportion of the surface covered by the patterns, is preferably between 10% and 80%, particularly between 20% and 70%, or even between 25% and 60%.

[0013] The invention also relates to a method for manufacturing a glazing described above, characterized in that each of the transparent enamel and the opaque enamel layer is deposited in a single screen-printing pass, and in that the transparent enamel and the opaque enamel layer are capable of being fired at identical temperatures, so that they are fired simultaneously in a single step. These features are such as to save time and energy.

[0014] Another object of the invention consists of the use of at least one glazing described previously as a spandrel to limit the warming of an urban environment due to the reflection of solar radiation on the facades of buildings.

[0015] The invention will be better understood from the following description of the accompanying drawings in which

[0016] [Fig. 1], respectively [Fig. 2], respectively [Fig. 3] are schematic cross-sectional views of two embodiments of glazing according to the first, respectively the second, respectively the third variant of the invention;

[0017] [Fig. 4] is the curve of the power of solar radiation over a measurement period of approximately three hours;

[0018] [Fig. 5] is the temperature curve of a bitumen floor at the base of different glazed structures aligned edge to edge in a vertical position, during the aforementioned measurement period; and

[0019] [Fig. 6] is the temperature curve of the glass of different glazing structures aligned under the aforementioned conditions and during the aforementioned period. With reference to Figure 1, a glazing sample according to the first embodiment of the invention (monolithic glazing) comprises a 30 cm x 30 cm, 6 mm thick sheet of clear glass 1, marketed by Société Saint-Gobain Glass under the registered trademark Planiclear®. On one face of the glass sheet 1, a grid of positive dots of transparent enamel 2, 0.4 mm in diameter and spaced 0.2 mm apart, has been deposited. On two different samples, transparent enamel 2 is obtained from a precursor marketed by the Vibrantz Company under the commercial reference 10198 (sample A), on the one hand, and from another precursor varying from this one in that it is slightly more refractory, designated hereafter by the name 10198' (sample B).These two transparent enamels are zinc-based and pigment-free. The precursor is applied by screen printing using a 120.34 mm screen; the deposited liquid thickness is approximately 20 to 27 µm. It is then fired in a kiln at 690 °C for 200 s. The thickness of the transparent enamel dots 2 after firing is approximately 20 µm, and the surface of these dots describes a slope of approximately 14° relative to the principal plane of the glazing (glass sheet 1). A continuous layer of opaque enamel 3 is then applied by screen printing using a 90.40 mm screen or equivalent over the transparent enamel dots 2, creating a texture; the wet thickness of opaque enamel 3 is 25 µm. A black enamel marketed by the Fenzi Company under the trade reference 1 L6026 is used as opaque enamel 3. Opaque enamel 3 is fired at 590 °C for 400 s.Thus, samples A (transparent enamel 2 = 10198) and B (transparent enamel 2 = 10198') were prepared, which will be the subject of measurements below, and correspond to the drawing on the left of figure 1.

[0020] Of these samples A and B, the glazing units conforming to the invention in the embodiment shown in the drawing on the right of Figure 1 differ only in the application of a layer or stack of layers of solar control 4 after the firing of the transparent enamel 2, and before the application of the opaque enamel layer 3. The layer or stack of layers 4 can be formed by magnetic field-assisted sputtering (magnetron sputtering), particularly under reduced pressure. This solar control coating 4 reflects infrared radiation from the sun, so as to limit the temperature increase induced by solar radiation inside the building. An example of such a solar control stack is marketed by Saint-Gobain Glass under the registered trademark COOL-LITE® SKN 175 II, which is used hereafter in a sample.

[0021] With reference to Figure 2, a glazing sample according to the second embodiment of the invention (laminated glazing) differs from that of Figure 1 in that, directly onto the transparent enamel texture 2 (left-hand drawing of Figure 2), or onto the solar control coating 4 directly covering the transparent enamel 2 (right-hand drawing of Figure 2), a second sheet of glass 5 is bonded to the first sheet of glass 1 by means of an interlayer adhesive layer (not shown), of the type polyvinyl butyral (PVB), thermoplastic polyurethane (TPU), or ethylene-vinyl acetate (EVA) copolymer. In the drawings, the dimensions of the transparent enamel texture 2 and the solar control coating 4 are enlarged for clarity.The intermediate adhesive layer flows during the assembly of the two glass panes, in such a way that its face on the left in both drawings conforms to the texture of the transparent enamel 2 (left drawing) and the solar control coating 4 (right drawing), and that its face on the right in both drawings conforms to the (flat) face of the second glass pane 5. The opaque enamel layer 3 is here deposited on the face of the second glass pane 5 opposite to the first glass pane 1.

[0022] With reference to Figure 3, a glazing sample according to the third variant of the invention (double glazing) differs from that of Figure 2 in that the laminated glazing is mounted in conjunction with a monolithic glazing consisting of a third sheet of glass 8, by means of an interlayer 6 maintaining them at a constant non-zero distance from each other, forming a layer of air or gas 7, which may contain desiccant (not shown) means. Instead of the face furthest from the first glass sheet 1 of the second glass sheet 5, it is the free face of the third glass sheet 8, i.e., the face opposite the air or gas layer 7, that is coated with the opaque enamel layer 3.

[0023] The samples A and B described previously, and conforming to the drawing on the left of Figure 1, are now evaluated in comparison with other opaque glazing structures that could constitute spandrels.These structures are: - sample C: 30 cm x 30 cm of 5 mm thick satin glass marketed by Saint-Gobain Glass under the registered trademark Satinovo® coated with the same black enamel by the same process as described above; the satin glass is obtained by chemical etching such as acid, it lets light through without being transparent; - sample D: 30 cm x 30 cm of 6 mm thick clear glass, marketed by Saint-Gobain Glass under the registered trademark Planiclear® coated with the same black enamel by the same process as described above; and - sample E: 30 cm x 30 cm of 6 mm thick clear glass, marketed by Saint-Gobain Glass under the registered trademark Planiclear® coated with a solar control layer marketed by Saint-Gobain Glass under the registered trademark COOL-LITE® SKN 175 II; this is a vision glass, transparent without an opaque enamel layer.

[0024] The color of samples A to D was measured with a CM600 spectrophotometer in SCE mode at an angle of incidence of 10° on the glass surface. The results are recorded in the table below.

[0025] Table 1

[0026]

[0027] With the textured transparent enamels 10198 and 10198', the opaque enamel is darker than without these textured enamels. Furthermore, because the Satinovo® glass is 5 mm thick instead of 6 mm for the other samples, the L* value indicates a darker character than with the textured transparent enamel 10198'.

[0028] Samples A to E were evaluated in the outdoor atmosphere for three hours. Figure 4 shows the solar radiation power in W / m². 2relative to time expressed in hours:minutes:seconds. Figure 5 represents the temperature measured on a bituminous surface at the base of samples aligned edge to edge in a vertical position, during the aforementioned three-hour period. Each sample is represented as follows:

[0029] - sample A: dashed or dotted line;

[0030] - sample B: continuous line;

[0031] - sample C: filled squares;

[0032] - Sample D: filled triangles; and

[0033] - Sample E: + signs.

[0034] The ground temperature is measured in front of each sample. The glass that warms the ground the most is sample E (transparent, untextured, with solar control stacking), due to its high energy reflectance. The second-best contributor to bitumen warming is sample D (opaque, but without textured transparent enamel). Compared to sample D, sample C (opaque, and satin-finished, i.e., textured by chemical etching) reduces the bitumen temperature by 0.62 °C, sample B (opaque, textured transparent enamel 10198') by 0.89 °C, and sample A (opaque, textured transparent enamel 10198) by 1.38 °C.

[0035] The temperature of the glass was also measured on samples A, C, D, and E to determine the energy absorption of each glass. These measurements are shown in Figure 6, where each sample is represented in the same way as in Figure 5. The sample with solar control stacking is less absorbent because it is transparent and highly reflective. The opaque sample with a chemically etched (satin) texture is more absorbent than the opaque sample with a transparent enamel texture according to the invention. The texture created with the transparent enamel preferentially reflects infrared radiation back into the sky, helping to reduce the urban heat island effect (UHI).

Claims

9 Demands 1. Glazing comprising at least one sheet of mineral glass (1) coated, on at least part of its surface, with a transparent enamel (2) textured according to surface patterns forming with the main surface of the sheet of mineral glass (1) angles between 5 and 90°, said glazing comprising a layer of opaque enamel (3), the transparent enamel (2) being in an intermediate position between the sheet of mineral glass (1) and the layer of opaque enamel (3).

2. Glazing according to claim 1, in which the transparent enamel (2) is directly coated with a solar control coating (4) between the transparent enamel (2) and the opaque enamel layer (3).

3. Glazing according to any one of the preceding claims, the main surface of which is divided into a first part comprising an opaque enamel layer (3) and a second part without an opaque enamel layer (3), and the first part constitutes a sill and the second part a glazing or vision glass.

4. Glazing according to claim 1, respectively claim 2, which is monolithic, and in which the opaque enamel layer (3) directly covers the transparent enamel (2), respectively the solar control coating (4).

5. Glazing according to claim 1, respectively claim 2, which is laminated, in which an intermediate adhesive layer directly covers the transparent enamel (2), respectively the solar control coating (4), in which a second sheet of mineral glass (5) directly covers the intermediate adhesive layer, and the opaque enamel layer (3) directly covers the second sheet of mineral glass (5).

6. Glazing according to claim 1, respectively claim 2, which is double, consisting of a laminated glazing and a monolithic glazing held at a constant distance from each other by an interlayer (6) so as to constitute an air or gas gap (7), in which in the laminated glazing, an adhesive interlayer layer directly covers the transparent enamel (2), respectively the solar control coating (4), and a second sheet of mineral glass (5) directly covers the adhesive interlayer layer, the second sheet of mineral glass (5) being in contact with the air or gas gap (7), and the monolithic glazing comprises a third sheet of mineral glass (8), the face of which opposite the air or gas gap (7) is coated with the opaque enamel layer (3).

7. Glazing according to any one of the preceding claims, wherein the transparent enamel (2) and the opaque enamel layer (3) are zinc borosilicate frits.

8. Glazing according to claim 1, in which the opaque enamel layer (3) contains at least one pigment such as chromium oxide Cr2O3, titanium dioxide TiC, copper oxide CuO.

9. Glazing according to any one of the preceding claims, wherein the transparent enamel (2) comprises mineral particles.

10. Glazing according to any one of the preceding claims, wherein the transparent enamel (2) is textured according to surface patterns forming angles between 10 and 90° with the main surface of the mineral glass sheet (1).

11. A method for manufacturing a glazing according to any one of the preceding claims, characterized in that each of the transparent enamel (2) and the opaque enamel layer (3) is deposited in a single screen printing pass, and in that the transparent enamel (2) and the opaque enamel layer (3) are suitable for being fired at identical temperatures, so that they are fired simultaneously in a single step.

12. Use of at least one glazing according to any one of claims 1 to 10 as a spandrel to limit warming of an urban environment due to the reflection of solar radiation on the facades of buildings.

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