Advances In Glazing Materials Essay Research Paper

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Advances In Glazing Materials Essay, Research Paper Table of Contents Section Page List of Figures 2 Introduction 3 Definitions 4 Current Options In Widow s Energy Efficiency 5 Understanding How Energy Moves Through Windows 5 Different ways Energy Travels 5 How is Energy in Windows Measured 6 R-values / U-values 6 Types Of Glazings In Windows 6 Low-e Glazing 7 Spectrally Selective Coatings 7 Heat-Absorbing Glazings 8 Reflective Coatings 8 Tomorrow s Options for More Efficient Windows 8 Superwindows 8 Summary/Conclusions 10 Recommendations 11 References Cited 12 List of Figures Figure Page 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 Introduction 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 changed greatly. Research and development into types of glazing have created a new generation of materials that offer improved window efficiency and performance for consumers. While this new generation of glazing materials quickly gains acceptance in the marketplace, the research and development of even more efficient technologies continues. Definitions Gas Fill A heavier-than-air gas such as argon or krypton is used to fill the space between panes to slow heat transfer. Glazing The glass

and/or plastic in a window unit that provides visibility yet blocks air leakage and some of the heat flow. Infrared Radiation Invisible radiation that humans perceived as heat. Low-e Coating Low-emissivity (low-e) coatings on glass surfaces reflect heat energy, but transmit visible light. Pyrolytic (Hard Coat) Low-e Durable metal oxides that are fused into the surface of window glass. Sputtered (Soft Coat) Low-e A coating on the inside pane of window glass in a sealed unit. It is made of reflective metal deposited in a vacuum. R-Value A measure of a window s resistance to heat flow. Total Solar Transmittance The total amount of all light spectra that is admitted by the window glazing. U-Value The amount of heat transmitted by the window. Center Of Glass R-Value/U-Value

Performance of a window measured through the center of the glass only; not the entire unit. Unit R-Value/U-Value A measure of thermal resistance/ heat transmittance for an entire window, including the frame. Visible Light Transmittance A measure of the amount of that portion of the total solar radiation visible to the human eye. Understanding How Is Energy Moves Through Windows Different Ways Energy Travels Understanding how windows work and how energy travels through them is the first step necessary to comprehend this concept of windows and energy. Windows start with the glass, or glazing. According to Krahn glazings do three basic things: They light in, they let you look out, and they isolate indoor environment from outdoors. (Wilson, p.94). Glass is transparent to sunlight, in

other words short wavelength radiation. Glass absorbs radiant heat, or long wavelength infrared radiation, warming up in the process. (Wilson, p.94). The glass radiates this heat both inside and outside. Figure 1. How Energy flows through windows: Radiation. Figure 2. How Energy flows through windows: Radiation. Figure 3. How Energy flows through windows: Conduction. How is Energy in Windows Measured R-Value / U-Value Manufacturers usually represent the energy efficiency of windows in terms of their U- values (conductance of heat) or their R-values (resistance to heat flow). If a window’s R- value is high, it will lose less heat than one with a lower R-value. Conversely, if a window’s U-value is low, it will lose less heat than one with a higher U-value. In other words, U-