Simple Glass
This material type should be used with caution. There may be significant differences in performance between glazing constructions using the simple glass layers versus detailed glass layers. It is meant to be used to describe an entire glazing system instead of creating a construction with individual layers. It should be used when very limited information is available on the glazing or when specific performance levels are being targeted.
The performance properties are U-factor, Solar Heat Gain Coefficient and optionally Visible Transmittance. The values for these performance indices can be selected to represent either glazing-only windows (with no frame) or an average window performance that includes the frame.
When a simple glass material is referenced in a fenestration construction, it cannot be used with other glazing or gas material layers. There will be important differences in the construction performance because the simple glazing system model includes its own special model for angular dependence when incident beam solar is not normal to the plane of the window.
Simple glass properties
U-Factor
This field describes the U-Factor or overall heat transfer coefficient. This is the rated (NFRC) value for U-factor under winter heating conditions. The U-factor is assumed to be for vertically mounted products. Although the maximum allowable input is U-7.0 W/m2K, the effective upper limit of the glazing generated by the underlying model is around U-5.8 W/m2K.
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Default value:
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Calculated
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Min & Max:
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0 < x <= 100,000
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Typical Range:
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1 to 7 W/(m2K); 0.01 to 1.0 to Btu/(hr °F)
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Units:
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W/(m2K); Btu/(hr °F)
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Solar heat gain coefficient
This field describes the value for SHGC, or solar heat gain coefficient. There are no units. This is the rated (NFRC) value for SHGC under summer cooling conditions and represents SHGC for normal incidence and vertical orientation.
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Default value:
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Calculated
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Min & Max:
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0 < x <= 100000
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Typical Range:
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0.2 – 1.5
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Units:
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N/A
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Visible transmittance
This field is optional. If it is omitted, then the visible transmittance properties are taken from the solar properties. If it is included, then the model includes it when developing properties for the glazing system. This is the rated (NFRC) value for visible transmittance at normal incidence.