Patent Description:
Vacuum insulated glass (VIG) units provides superior insulating properties. A VIG unit normally comprises a pair of glass sheets separated by a gap between the glass sheets, and a plurality of support structures such as pillars are distributed in the gap. An edge seal, such as a rigid edge seal seals the gap at the periphery of the VIG unit. The edge sealing may comprise a solder glass material or a metal solder material, and the gap is normally evacuated to a pressure below <NUM>-<NUM> bar, such as below <NUM>-<NUM> bar, e.g. to about or below <NUM>-<NUM> mbar, and the support structures in the gap helps to maintain the gap.

A VIG unit may for safety reasons be laminated at one, or both, of the sides in order to avoid glass falling down in case a glass sheet of the VIG unit breaks. Further, using laminated glass in a VIG unit may improve the performance of the VIG unit in other ways. One such improvement can be noise abatement since noise problems in our environment is a growing problem today due to denser build environment, more automobiles in the streets etc. VIG units are for instance known from <CIT>, <CIT> and <CIT>.

Further, a specific noise problem is observed when it rains. This is specifically a problem with roof windows.

The present disclosure provides an improved solution for a roof window with a laminated VIG unit for noise abatement when it rains.

The present invention relates in one aspect to a roof window according to claim <NUM>, comprising a frame and a laminated vacuum insulated glass (laminated VIG) unit fixed in said frame, the laminated VIG unit comprising:.

Tests has shown that roof windows has acoustic noise problems, for example when it rains, specifically in an interval that is audible for the human ear, where the sound is perceived as a high pitch. This is also shown in <FIG>.

To minimise these noise problems, the inventors has developed a roof window with a lamination layer which when exposed to impacts such as sound waves; the fluctuation in decibel (dB) over a range of <NUM> in the interval from <NUM> to <NUM> will not exceed <NUM> dB.

Hence, the roof window according to the present invention minimises these resonance peaks.

Various examples are described hereinafter with reference to the figures. It should also be noted that the figures are only intended to facilitate the description of the examples.

In addition, an illustrated example needs not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular example is not necessarily limited to that example and can be practiced in any other examples even if not so illustrated, or if not so explicitly described.

The roof window will have properties that dampens the noise induced by impacts hitting the rood window, such as rain. This will improve the overall acoustic comfort for humans. It is seen that when the roof window is exposed to impacts such as rain, fluctuation peaks in decibel (dB) over a range of <NUM> in the interval from <NUM> to <NUM> will not exceed <NUM> dB.

By the present invention, it is possible to obtain a roof window having improved acoustic insulation, while at the same time maintaining satisfactory characteristics in terms of rigidity, finesse of the look, and light transmission. The improvement of the acoustic insulation/dampening is significant and in particular at the frequency of coincidence, where the glazing usually has a drop in sound insulation performance.

In one or more embodiments, said further sheet may be a glass sheet such as an annealed glass sheet. Annealed glass sheets may have a more plane surface structure, and may be cost efficient to use. In one or more embodiments, said further sheet may be a tempered glass sheet. In one or more embodiments, said further sheet may be a float glass sheet.

In one or more embodiments, the lamination layer comprises a third layer sandwiched in between the first layer and the second layer. The third layer sandwiched in between the first layer and the second layer may be softer than the first layer and the second layer. In one or more embodiments, the third layer is having a glass transition temperature of lower degrees than the first layer and the second layer.

In one or more embodiments, the third layer is of a polymer material.

In one or more embodiments, the polymer material is selected from polyvinyl butyral (PVB) or vinyl acetate-ethylene (EVA).

In one embodiment all three layers are of a PVB material where the third layer is of a flexible PVB material, arranged between the first and the second layer of standard PVB.

The term "standard PVB" in the present application means PVB whose molar content of vinyl butyral units (VB) is included in the following ranges:
the molar level of BV is greater than <NUM>%, such as greater than <NUM>%, such as greater than <NUM>%, such as greater than <NUM>%, such as greater than <NUM>%, such as greater than <NUM>%, such as greater than <NUM>%, and less than <NUM>%, such as less than at <NUM>%, such as less than <NUM>%, such as less than <NUM>%, such as less than <NUM>%, such as less than <NUM>%, based on the total number of monomer units of the PVB, the mass content of plasticizers expressed in parts per <NUM> parts of PVB resin (phr) is greater than <NUM> phr, such as greater than <NUM> phr, such as greater than <NUM> phr, such as greater than <NUM> phr, such as greater than <NUM> phr, and is less than <NUM> phr, such as less than <NUM> phr, such as less than <NUM> phr, such as less than <NUM> phr, such as less than <NUM> phr, such as less than <NUM> phr, such as less than <NUM> phr, such as less than <NUM> phr, such as less than <NUM> phr, the glass transition temperature for a frequency of <NUM>, is greater than <NUM>, such as greater than <NUM>, and is less than <NUM>, such as less than <NUM>.

For a given frequency, the tan δ value reaches its maximum value at a temperature, called the glass transition temperature or glass transition point. This tan δ value can be estimated using a viscoanalyzer or other suitable known device. The tan δ value corresponds to a technical characteristic of the nature of a material and reflects its ability to dissipate energy, especially acoustic waves. The tan δ value varies as a function of the temperature and the frequency of the incident wave.

In one or more embodiments, the third layer is having a tan δ value greater than or equal to <NUM>, at <NUM> in a frequency range between <NUM> and <NUM>.

In one or more embodiments, the tan δ value of the third layer is greater than or equal to <NUM>, such as <NUM>, such as <NUM>, such as <NUM>, such as <NUM>, such as <NUM>. The tan δ value is generally less than <NUM>. By having a third middle layer with a relatively higher tan δ value may improve the acoustic insulation performance of the window.

In one or more embodiments, the third layer has a shear parameter g = G '/e of between <NUM> × <NUM><NUM> and <NUM> × <NUM><NUM> Pa/m such as between <NUM> × <NUM><NUM> and <NUM> × <NUM><NUM> Pa/m, at <NUM> in the frequency range of between <NUM> and <NUM> - G 'being the shear modulus of the inner third layer and e being the thickness of the inner third layer. The mechanical characteristics in shear as defined here gives the third layer a satisfactory rigidity and acoustic insulation performance.

In one embodiment, a layer of PVB (the third layer) having a glass transition temperature of <NUM> is sandwiched between two layers of PVB (the first and the second layer) having a glass transition temperature of <NUM>.

In one or more embodiments, a first and a second barrier layer is arranged respectively between said first layer and said third layer and between said second layer and said third layer, and may be composed of a viscoelastic plastic material, preferably polyester, such as polyethylene terephthalate (PET). The barrier layer may prevent any chemical diffusion between the inner third layer, and the two outer layers - the first and the second layer. According to a particular embodiment, at least one of these barrier layers is composed of PET. In one or more embodiment the barrier layers each have a thickness of between <NUM> and <NUM>, preferably between <NUM> and <NUM>, preferably between <NUM> and <NUM>.

In one or more embodiments, at least one of the layers in the lamination layer is a polyethylene terephthalate (PET) material.

In one or more embodiments, the fluctuation in dB over a range of <NUM> in the interval from <NUM> to <NUM> will not exceed <NUM> dB.

In the frequency range between <NUM> and <NUM>, which is the range where the human ear is the most sensitive, the improvement of the acoustic insulation/dampening is significant.

In one or more embodiments, the fluctuation in dB over a range of <NUM> the interval from <NUM> to <NUM> will not exceed <NUM> dB.

In one or more embodiments, the fluctuation in dB over the whole range of <NUM> in the interval from <NUM> to <NUM> will not exceed <NUM> dB.

In one or more embodiments, the lamination layer provides an at least 5dB local dampening over said range of <NUM> when compared to frequencies above and/or below said range of <NUM>, when compared to a similar laminated VIG unit laminated with a single layer PVB material having a thickness between <NUM> and <NUM>.

In one or more embodiments, the lamination layer provides an at least 5dB local dampening over said range of <NUM> when compared to frequencies above and/or below said range of <NUM>, when compared to a similar laminated VIG unit laminated with a standard acoustic PVB layer.

A standard acoustic PVB layer could e.g. be consisting of three layers of PVB, the outer two layers being standard PVB and the middle layer being a PVB plasticised with triethylene glycol bis-<NUM>-ethylhexanoate.

In one or more embodiments, the lamination layer provides an at least 5dB local dampening over said range of <NUM> when compared to frequencies above and/or below said range of <NUM>, when compared to a laminated VIG unit laminated with a lamination layer having some of the same properties in regards to acoustic dampening performance.

In one or more embodiments, the thickness of the lamination layer is between <NUM> and <NUM>, such as between <NUM> and <NUM>, such as between <NUM> and <NUM>.

In one or more embodiments, the thickness of the third layer of the lamination layer is between <NUM> and <NUM>, such as between <NUM> and <NUM>, such as between <NUM> and <NUM>.

In one or more embodiments, the thickness of the third layer of the lamination layer is between <NUM> and <NUM>, such as between <NUM> and <NUM>, such as between <NUM> and <NUM>, such as between <NUM> and <NUM>, such as between <NUM> and <NUM>.

In one or more embodiment, the third layer may be obtained from an aqueous emulsion of at least one polymer material.

In one or more embodiment, the third layer may be a polymerization product of one or more polymers.

In one or more embodiment, the third layer may be a polymerization product of one or more polymers selected from an allyl compound, a vinyl compound, an acrylate compound, a methacrylate compound, an acrylic compound, an acrylamide compound or, a methacrylamide compound.

In one or more embodiment, the third layer may be a polymerization product of two acrylate compounds.

In one or more embodiments, the third layer may be obtained from an aqueous emulsion of at least two polymers e.g. acrylate and acrylic, structured in interpenetrating networks. One example of such an aqueous emulsion of at least two polymers e.g. acrylate and acrylic, is QuickGlue®.

In one or more embodiments, the thickness of the first and/or second layer of the lamination layer is greater than <NUM>, such as between <NUM> and <NUM>, such as between <NUM> and <NUM>, such as between <NUM> and <NUM>.

In one or more embodiments, the three layers in the lamination layer is not of equal thickness. In one embodiment, the first layer and the second layer are of equal thickness and the third layer is of a different thickness than the first layer and the second layer. In one embodiment, the third layer is of less thickness than the first layer and the second layer.

The three layers in the lamination layer may in one embodiment have different characteristics such as different composition, plasticiser ratio, treatment or other measurable characteristics. Hence, in one embodiment, each layer will have a characteristic response to vibration. In one embodiment, the first layer and the second layer have the same characteristics.

The thickness of the glass sheets may be between <NUM>-<NUM>, or between <NUM>-<NUM>, or between <NUM>-<NUM>, or between <NUM>-<NUM>.

In one or more embodiments, the first glass sheet and the second glass sheet are tempered, such as thermally tempered glass sheets.

The term "tempered glass sheet" as used herein is understood to mean glass sheets in which compressive stresses have been introduced in the surface(s) of the glass sheet. For glass to be considered strengthened this compressive stress on the surface(s) of the glass can be a minimum of <NUM> MPa (<NUM>,<NUM> psi) and may be higher than <NUM> MPa. The VIG is heated during production in order to form the periphery seal etc. and some glass strength may be annealed or lost during manufacture.

In one or more examples, the tempered glass sheets have been tempered by thermal tempering, chemical tempering, plasma tempering, or a combination comprising at least one of the foregoing.

Tempered glass, also known as toughened glass, may be produced from annealed glass by means of a strengthening procedure, which e.g. may be thermal tempering, chemical tempering, or plasma tempering with the purpose of introducing the compressive stresses into the surface(s) of the glass sheet. After tempering, the stress developed by the glass can be high, and the mechanical strength of tempered glass can be four to five times greater than that of annealed glass.

The tempered glass sheets may have been tempered by thermal tempering. Thermally tempered glass may be produced by means of a furnace in which an annealed glass sheet is heated to a temperature of approximately <NUM>-<NUM>, after which the glass sheet is rapidly cooled. The cooling introduces the compressive stresses into the glass sheet surface(s).

A chemical tempering process involves chemical ion exchange of at least some of the sodium ions in the glass sheet surface with potassium ions by immersion of the glass sheet into a bath of liquid potassium salt, such as potassium nitrate. The potassium ions are about <NUM>% larger in size than the replaced sodium ions, which causes the material at the glass sheet surfaces to be in a compressed state. In this process, typically by immersion of the glass sheet into a molten salt bath for a predetermined period of time, ions at or near the surface of the glass sheet are exchanged for larger metal ions from the salt bath. The temperature of the molten salt bath is typically about <NUM>-<NUM> and the predetermined time period can range from about two to ten hours. The incorporation of the larger ions into the glass strengthens the sheet by creating a compressive stress in a near surface region. A corresponding tensile stress is induced within a central region of the glass to balance the compressive stress.

Plasma tempering of glass sheets resembles the chemical tempering process in that sodium ions in the surface layers of the glass sheet are replaced with other alkali metal ions so as to induce surface compressive stresses in the glass sheet, the replacement is however made by means of plasma containing the replacement ions. Such method may be conducted by using a plasma source and first and second electrodes disposed on opposing major surfaces of a glass sheet, wherein the plasma comprises replacement ions, such as potassium, lithium, or magnesium ions, whereby the replacement ions are driven into the opposing surfaces of the glass sheet so as to increase the strength of the sheet.

In one or more embodiments, the thermal transmittance measured as a U-value ([W/(m<NUM>)(K)]), of the laminated VIG unit is below <NUM>, such as below <NUM> or below <NUM>. These values are when measure at the centre of the VIG unit.

In one or more embodiments, the distance between neighbouring structures of the plurality of support structures is larger than or substantially equal to <NUM>, such as larger than or substantially equal to <NUM>. In one or more embodiments, the distance between neighbouring structures of the plurality of support structures is larger than or substantially equal to <NUM>, such as larger than or substantially equal to <NUM>. The distance between support structures may be measured from an outer edges of adjacent support structures. Alternatively, the distance between support structures may be measured from the centres of adjacent support structures. The support structure-to-support structure distance can be the same or different between each adjacent support structures. The support structures may have a height of <NUM> to <NUM>, such as between <NUM> to <NUM>, or between <NUM> to <NUM>. In one or more examples, the support structures have the same height. This keeps the production cost low as only one type of support structure is needed. The tool used for positioning the support structures on the glass pane will further not need to have individual settings for placing support structures with a difference in height.

The support structures may alternatively have the different heights, including at least two different heights. As the distance between the two glass sheets may vary from region to region in VIG unit, a difference in height of the support structures will allow for compensation of these distance variations. In one or more examples, each support structures independently has a height of <NUM> to <NUM>, such as <NUM> to <NUM>, or such as <NUM> to <NUM>.

The support structures may have a width of between <NUM> to <NUM>, or between <NUM> to <NUM>, such as between <NUM> to <NUM>. Again, the width of the individual support structures may be the same or may be different.

The support structure can be any suitable material, for example solder glass, a polymer (e.g., Teflon), plastic, ceramic, glass, metal, or the like. In one or more examples, the support structure comprises a steel or a solder glass.

In one or more embodiments, the thickness of the evacuated gap is between <NUM> and <NUM>, such as between <NUM> and <NUM>, such as around <NUM> or around <NUM>.

Any suitable side seal material known in the industry can be used to seal the VIG unit. The side seal material may be a soldering material, for example a glass solder frit material. The glass solder frit material may have a low melting temperature, wherein thermal treatment can be used to hermetically seal the periphery of the VIG unit.

In one or more embodiments, the laminated VIG unit has a has a size of at least <NUM><NUM>, such as at least <NUM><NUM>, for example at least <NUM><NUM> such as at least <NUM><NUM>, and/or wherein the major surfaces of the VIG unit has a rectangular shape.

In one or more embodiments, the laminated VIG unit has a has a size of between <NUM><NUM> and <NUM><NUM>.

In one or more embodiments, the impacts exposed to the roof window is rain.

It will be understood that, although the terms "first," "second," "third," and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element.

"About" "around" or "approximately" as used herein is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art, considering the measurement in question and the error associated with measurement of the particular quantity (i.e., the limitations of the measurement system).

Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which this invention pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined in the present specification.

In relation to the figures described below, where the present disclosure may be described with reference to various embodiments, without limiting the same, it is to be understood that the disclosed embodiments are merely illustrative of the present disclosure that may be embodied in various and alternative forms, within the limits defined by the claims. The figures are not to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for e.g. teaching one skilled in the art to variously employ the present disclosure.

<FIG> illustrates acoustic measurements of a laminated (standard lamination layer) VIG unit made in a sound lab. The measurements are obtained by measuring the impact of a rain source by a microphone (see ad <NUM> below). The graph is a replicate of a test-graph. It can be seen from the acoustic measurement that the VIG unit has acoustic noise problems, specifically in an interval that is audible for the human ear, where the sound is perceived as a high pitch.

In general, measurement frequency response can be measured in a couple of ways:.

At the interface of the window/glass pane, vibrational movement energy is converted to air pressure. The movement of air at frequencies and amplitudes where the human ear is sensitive, is then transported through and perceived as sound. The most common way to quantify this is through a microphone where a membrane that is sensitive for air pressure is converted to an electrical signal. Microphones can be placed in the near field < <NUM> or in the far field ><NUM>, at different locations angled towards the window. Near field measurements are less sensitive for sound from other sources but can have the drawback to pick up sound that is localised meaning that a slight shift in the position can result in a different measurement.

Far field measurement can suffer the same if the source of the sound is from multiple sources that are in phase or slightly out of phase in which case the power of sound becomes directional depending on the amount of sources. In the case of a normal, uniform pane, it is assumed that the source is one single source and far field measurements if done in an anechoic chamber will give reliable results. The measurement are done in two adjacent chambers where in one chamber a source is positioned and in the other chamber, a microphone. In the interface between the chambers a building element is placed and made air tight. A measurement is then carried out where the result is expressed in dB-loss through the building element by substracting the recorded power from the microphone from the output power from the source. Those measurements are standardised (see the below list in table <NUM>) and refer to these standards on the specifics.

Typically rain noise measurement is performed in this manner and consist of a rain source positioned x-meter above a window. The window is built in a small chamber facing the rain source. A microphone is positioned in that chamber in the near field because of the sound pressure level being in the lower end. This measurement is standardised (see the below list in table <NUM>).

In order to measure vibration, an accelerometer is attached to the VIG unit with e.g. bee wax. The accelerometer measures the displacement in the x-y-z planes in the frequency range that is audible for the human ear. The accelerometer used, expresses the vibration (m^<NUM>/s) into decibels (dB) being the same domain as for sound pressure. The type of measurement is used to determine eigenfrequencies for constructions in general, but in this case for glass. The intention is to reveal all the eigenfrequencies fitting to the glass including the eigenfrequencies or change in eigenfrequencies when mounted in a window construction. Measurements should in principle correlate with measurements performed with a microphone but measurements are taken in the stadium where vibration is not turned into sound yet.

In combination with either an accelerometer or a microphone, the resulting response of an impacting source can be measured. One way of doing this is by using a pendulum where the end of the pendulum an aluminium ring was mounted. Measurement was carried out in a box made to be as anechoic as possible with sound dampening material mounted on the inside. The VIG was mounted in a vertical position against the box and an accelerometer mounted on the VIG at the side facing the inside of the box. The impingement generates a frequency spectrum that can be analysed and correlated to the impact of rain on a similar construction without using rain. A similar measurement can be done with a microphone mounted in the box.

A so-called exciter is used to impose vibration onto a pane. An exciter is a loudspeaker where the membrane (or cone) has not been mounted but a flat surface created instead, allowing for mounting this on different surfaces. Exciters can then impose vibrations with varying frequencies and power as this is directly connected to an amplifier typical to a hifi stereo. For measurements of the response of VIG's, an exciter is mounted underneath and contact is assured, either by applying the proper force, of gluing it. The VIG lies flat and a frequency sweep is carried out. In order to visualise the response, white powder was evenly distributed over the VIG.

The outcome of these measurements showed localisation of the vibration. The intensity of vibrations measured between pillars are different from those on the pillars as the powder starts to collect at the pillars at specific frequencies and intensities.

<FIG> illustrates schematically one example of a roof window. The roof window <NUM> comprises an adjustable sash <NUM> with an insulated glass pane <NUM> arranged therein. The sash <NUM> in the example of <FIG> is a "center pivot" sash, but it may also in other embodiments of the present disclosure be a top-hinged sash. The sash <NUM> is configured to be moved at a hinged connection, relative to a fixed frame part <NUM> attached/fixed to a roof construction or the like. The roof construction can be any kind of roof constructions, e.g. a roof with a steep slope or inclination or a roof with almost none or very little inclination. In one embodiment, the inclination can be from <NUM> degree to <NUM> degree, or such as from <NUM> degree to <NUM> degree.

In further embodiments of the present disclosure (not illustrated), the window <NUM> may be a horizontal window configured to be arranged in a flat roof of a building.

As can be seen, the system in <FIG> also comprises an architectural covering <NUM>, in this example a roller shutter, but it may also be a blind such as a venetian blind, a roller blind or the like in further embodiments. The system may also not comprise an architectural covering.

<FIG> illustrates schematically, in a cross sectional view, a lamination assembly for providing a laminated VIG unit of a roof window according to embodiments of the present disclosure.

The lamination assembly <NUM> comprises a vacuum insulated glass (VIG) unit <NUM>. The VIG unit <NUM> comprises two glass sheets 11a, 11b separated by a plurality of support structures <NUM> distributed in a gap <NUM> between the tempered glass sheets 11a, 11b. An edge sealing <NUM> made from e.g. a soldering material such as a low temperature solder glass material which may be lead free, or alternatively a metal seal, extend between the glass sheets and enclose the gap <NUM> so it is sealed. The gap <NUM> may be evacuated to a pressure below <NUM>-<NUM> bar such as at or below <NUM>-<NUM>, <NUM>-<NUM> or <NUM>-<NUM> mbar. The evacuation of the gap <NUM> may e.g. have been established, prior to the lamination, through an evacuation opening (not illustrated in the figures) in one of the glass sheets 11a, 11b which is subsequently sealed to maintain the reduced pressure in the gap <NUM>. One or both of the glass sheets 11a, 11b may be tempered glass sheets such as thermally tempered glass sheets in embodiments of the present disclosure.

The distance D1 between neighbouring support structures <NUM> of the plurality of support structures <NUM> in the evacuated gap <NUM> may in embodiments of the present disclosure be larger than or substantially equal to <NUM>, such as larger than or substantially equal to <NUM>, for example larger than or substantially equal <NUM> or <NUM>.

The lamination assembly <NUM> moreover comprises a lamination layer <NUM> arranged between an outer surface of the tempered glass sheets 11b of the VIG unit <NUM> and a further sheet <NUM> of the lamination assembly <NUM>. The further sheet <NUM> may in one or more embodiments of the present disclosure be an annealed glass sheet, it may be a thermally tempered glass sheet, it may be a hard polymer plate transparent to light in the visible range and/or the like, it may be a float glass sheet.

The lamination layer may be according to any one of the disclosed embodiments of the present disclosure. In this figure, the lamination layer <NUM> is illustrated as comprising three layers.

It is to be understood that the outer surfaces may be coated with a coating layer (not illustrated) in one or more embodiments of the present disclosure.

While the present disclosure has been described in detail in connection with only a limited number of embodiments or aspects, it should be readily understood that the present disclosure is not limited to such disclosed embodiments or aspects. Rather, the present disclosure can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate in scope with the claims.

Additionally, while various embodiments or aspects of the present disclosure have been described, it is to be understood that aspects of the present disclosure may include only some of the described embodiments or aspects or combinations of the various embodiments or aspects, within the limits defined by the claims.

Claim 1:
A roof window (<NUM>) comprising a frame and a laminated vacuum insulated glass (laminated VIG) unit (<NUM>) fixed in said frame, the laminated VIG unit (<NUM>) comprising:
a first glass sheet (11b) and a second glass sheet (11a), wherein the first and second glass sheets are separated by an evacuated gap (<NUM>), and wherein a plurality of support structures (<NUM>) are distributed inside the evacuated gap (<NUM>) between the first and second glass sheets, a lamination layer (<NUM>) arranged between the first glass sheet (11b) and a further sheet (<NUM>), said lamination layer (<NUM>) is bonding to an outer major surface of the first glass sheet facing the evacuated gap, wherein the lamination layer (<NUM>) comprises at least a first layer and a second layer of a polymer material,
wherein the lamination layer (<NUM>) provides that the fluctuation in decibel (dB) over a range of <NUM> in the interval from <NUM> to <NUM> will not exceed <NUM> dB when the roof window is exposed to impacts.