Double-glazed, Clear GlassThis figure illustrates the performance of a typical double-glazed unit with two lites of clear glass. The inner and outer layers of glass are both clear and separated by an air gap. Double glazing, compared to single glazing, cuts heat loss in half due to the insulating air space between the glass layers. In addition to reducing the heat flow, a double-glazed unit with clear glass will allow the transmission of high visible light and high solar heat gain. |
Center of Glass Properties Note: These values are for the center of glass only. They should only be used to compare the effect of different glazing types, not to compare total window products. Frame choice can drastically affect performance. These values represent double glazing with a 1/2" air gap. Aluminum units use 3/8" air gap, where the U-factor is 0.52 and the SHGC and VT remain the same. |
Whole Window Properties - Double-glazed, Clear Glass
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 |
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Frame |
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U-Factor |
0.71-0.99 |
0.56-0.70 |
0.41-0.55 |
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SHGC |
>0.60 |
>0.60 |
0.41-0.60 |
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VT |
>0.60 |
>0.60 |
0.51-0.60 |
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Note: The thermal performance properties of specific glazings and frames can vary depending on product design and materials. The results presented here are averages. Consult specific manufacturers for NFRC rated U-factors and SHGCs for products of interest. |
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Skylight Properties - Double-glazed, Clear Glass
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Frame |
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U-Factor |
>0.90 |
|
0.71-0.90 |
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SHGC |
>0.60 |
|
>0.60 |
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VT |
>0.65 |
|
>0.60 |
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Note: The thermal performance properties of specific glazings and frames can vary depending on product design and materials. The results presented here are averages. Consult specific manufacturers for NFRC rated U-factors and SHGCs for products of interest. |
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Single-glazed, Clear Glass |
Single-glazed, Tinted Glass
Double-glazed, Clear Glass |
Double-glazed, Tinted Glass |
Double-glazed, High-performance Tinted Glass
Double-glazed, High-solar-gain Low-E Glass, Argon/Krypton Gas |
Double-glazed, Moderate-solar-sain Low-E Glass, Argon/Krypton Gas |
Double-glazed, Low-solar-gain Low-E Glass, Argon/Krypton Gas
Triple-glazed, High-solar-gain Low-E Glass, Argon/Krypton Gas |
Triple-glazed, Low-Solar-Gain Low-E Glass, Argon/Krypton Gas
Glazing Types | Frame Types | Operating Types | Low-E Coatings | Gas Fills | Spacers