An insulated glass unit to be used in a fenestration product of a building, the insulated glass unit comprising: a frame; a suspended particle device, SPD, laminate mounted in the frame on an outward facing side of the insulated glass unit; and a pane of glass mounted in the frame adjacent to the laminate such that a space is formed between the laminate and the pane of glass; wherein the space is filled with argon, wherein the SPD laminate comprises: a first substantially transparent panel; a first adhesive layer applied to an inner surface of the first transparent panel; an SPD film with a first surface adhered to the first substantially transparent panel via the first adhesive layer; characterised in that the SPD laminate further comprises a second adhesive layer applied to a second surface of the SPD film opposite the first surface; and a second substantially transparent panel adhered to the SPD film via the second adhesive layer to face the argon filled space, wherein the first substantially transparent panel is a pane of tempered glass and the second substantially transparent panel is a pane of heat rejecting glass, wherein a heat rejecting coating on the pane of the heat rejecting glass is positioned on the pane of heat rejecting glass to face away from the SPD film, wherein said insulated glass unit has a winter U-value, which represents the rate of non-solar heat loss or gain through a material, of <1.70 W/(m 2 K) and a solar heat gain coefficient, SHGC, which represents the fraction of solar radiation admitted through a window, both directly transmitted and absorbed, and subsequently released inward, of <0.30, wherein the winter U-value is determined under the following conditions: outside temperature of -17.8°C, room temperature of 21.1 °C, windspeed of 6.7 m/s and no solar load. a frame; a suspended particle device, SPD, laminate mounted in the frame on an outward facing side of the insulated glass unit; and a pane of glass mounted in the frame adjacent to the laminate such that a space is formed between the laminate and the pane of glass; wherein the space is filled with argon, wherein the SPD laminate comprises: a first substantially transparent panel; a first adhesive layer applied to an inner surface of the first transparent panel; an SPD film with a first surface adhered to the first substantially transparent panel via the first adhesive layer; characterised in that the SPD laminate further comprises a second adhesive layer applied to a second surface of the SPD film opposite the first surface; and a second substantially transparent panel adhered to the SPD film via the second adhesive layer to face the argon filled space, wherein the first substantially transparent panel is a pane of tempered glass and the second substantially transparent panel is a pane of heat rejecting glass, wherein a heat rejecting coating on the pane of the heat rejecting glass is positioned on the pane of heat rejecting glass to face away from the SPD film, wherein said insulated glass unit has a winter U-value, which represents the rate of non-solar heat loss or gain through a material, of <1.70 W/(m 2 K) and a solar heat gain coefficient, SHGC, which represents the fraction of solar radiation admitted through a window, both directly transmitted and absorbed, and subsequently released inward, of <0.30, wherein the winter U-value is determined under the following conditions: outside temperature of -17.8°C, room temperature of 21.1 °C, windspeed of 6.7 m/s and no solar load. a first substantially transparent panel; a first adhesive layer applied to an inner surface of the first transparent panel; an SPD film with a first surface adhered to the first substantially transparent panel via the first adhesive layer; characterised in that the SPD laminate further comprises a second adhesive layer applied to a second surface of the SPD film opposite the first surface; and a second substantially transparent panel adhered to the SPD film via the second adhesive layer to face the argon filled space, wherein the first substantially transparent panel is a pane of tempered glass and the second substantially transparent panel is a pane of heat rejecting glass, wherein a heat rejecting coating on the pane of the heat rejecting glass is positioned on the pane of heat rejecting glass to face away from the SPD film, wherein said insulated glass unit has a winter U-value, which represents the rate of non-solar heat loss or gain through a material, of <1.70 W/(m 2 K) and a solar heat gain coefficient, SHGC, which represents the fraction of solar radiation admitted through a window, both directly transmitted and absorbed, and subsequently released inward, of <0.30, wherein the winter U-value is determined under the following conditions: outside temperature of -17.8°C, room temperature of 21.1 °C, windspeed of 6.7 m/s and no solar load.