Glazing Types – Double Glazed Windows

double glazed clear glass

Double-Glazed Windows, Clear Glass

A typical clear, double-glazed unit has two lites of glass, with the inner and outer layers of glass both being 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.

Whole Window Properties – Double-Glazed, Clear Glass

double glazed tinted glass

Double-Glazed, Tinted Glass

A typical double-glazed unit with bronze or gray tinted glass has two lites of glass with the the outer layer of glass being bronze or gray tint and the inner layer being clear. These two layers are 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. Bronze and gray tinted glass products are similar in energy performance. The primary purpose of the bronze or gray tint is to reduce solar heat gain. But, it also reduces visible light transmission compared to clear glass or even other standard tinted glass products, such as green and blue tints, which offer significantly higher visible light transmission. Tinted glass is useful in controlling glare, but solar heat gain and visible light transmission may be reduced relative to the performance of alternate glazing options, such as low-E glass with moderate or low solar gain.

The tint has no effect on the U-factor but reduces solar gain, which may be a benefit in the summer and a liability in the winter, depending on local climate conditions.

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.

Whole Window Properties – Double-Glazed, Tinted Glass

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provides unbiased information and education to the public on the energy efficiency, technical, and human considerations that influence window selection and use. The EWC collaborates with allied organizations, educational institutions, and government agencies that promote energy efficiency in residential windows. We do not sell, service, install, or recommend products, or endorse manufacturers. Descriptions and specifications of the products in the Window Selection Tool are provided by the manufacturer. The EWC is not liable for any manufacturing defects or inaccurate product descriptions and specifications and does not guarantee the performance of NFRC-certified windows, doors, and skylights.

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