advances in glazing materials

Understanding How Energy Moves Through Windows 5

Tomorrow’s Options for More Efficient Windows 8

1. How energy flows through windows: Radiation 6

2. How energy flows through windows: Convection ………………………………...…….6

3. How energy flows through windows: Conduction……………………………………….7

4. Three Routes to Switchable Windows. 10

Until recently, clear glass was the primary glazing material used in windows. Although

glass is durable and allows a high percentage of sunlight to enter buildings, it has very little

resistance to heat flow. During the past two decades, though, glazing technology has

Research and development into types of glazing have created a new generation of mat

. . .
How much does energy cost: in Califiornia for example where the rate for electricity per kilowatt-hour will be the most expensive in the nation, one can justify spending a lot more on energy efficient windows than if you live in Colorado where is cheap.

Visible Light Transmittance – A measure of the amount of that portion of the total solar radiation visible to the human eye.

Infrared Radiation – Invisible radiation that humans perceived as heat. Three Routes to Switchable Windows

Lawrence Berkley Laboratory’s Selkowitz thinks that electrochromics should be far easier to sell than low-e, or emissivity, windows, which already appear in more that 25 percent of the new commercial and residential windows. But the energy performance of hard-coat low-e films is slightly poorer than

that of soft-coat films.

Gray- and bronze-tinted windows reduce the penetration of both light and heat into

buildings in equal amounts (i. This first generation of superwindows now

available have a center-of-glass R-value of 8 or 9, but have an overall window R-value of

only about 4 or 5 because of edge and frame losses. The coatings typically face air spaces within windows and reduce heat flow-between

the panes of glass. (Wilson, 1993)

Spectrally Selective Coatings

Spectrally selective (optical) coatings are considered to be the next generation of low-e technologies. Your microclimate: One might live in a part of the country that is generally warm, but your house might be in a cold spot-for example, on the noth side of a hill where is it always windy. Soft-coat low-e films degrade when

exposed to air and moisture, are easily damaged, and have a limited shelf life, so they are

carefully applied by manufacturers in insulated multiple-pane windows. Heat- absorbing glass reflects only a small percentage of light and therefore does not have the mirror-like appearance of reflective glass. Glass absorbs radiant heat, or long wavelength infrared radiation, warming up in the process. (Wilson, 1993)

Tomorrow’s Options for More Efficient Windows

Superwindows

"Superwindows" now coming on the market can attain high thermal resistance by combining multiple low-e coatings; low-conductance gas fills; barriers between panes, which reduce convective circulation of the gas fill; and insulating frames and edge spacers.

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Approximate Word count = 1793
Approximate Pages = 7 (250 words per page double spaced)

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