COMMON MATERIALS AND OF fiCE SUPPLY PRODUCTS:TI NTED WINDOWS.

TI NTED WINDOWS

As energy consumption continues to grow in the United States, companies are looking to make homes more energy efficient. It is estimated that 2 percent of all energy consumed can be attributed to the inefficiency of household windows. Improving window technology could save billions of dollars spent on heating, lighting, and cooling costs for consumers nationwide. The concept of adjustable darkness windows in households began with the development of photochromic materials. Photochromic materials darken upon exposure to light and block ultraviolet radiation from the sun, reducing the strain on your air conditioner in the summer. These materials have been used for some time in consumer eyewear but have not made the transition to window coatings. The main reason is that such windows respond to light only and are not manually controlled. During the winter, photochromic windows would also exclude desirable warming ultraviolet radiation. An adjustable window film that could be darkened or lightened depending on conditions would be ideal to reduce energy consumption regardless of the season. Liquid crystalline displays (LCDs), which are found in watches, computers, and a variety of other electronic devices, work by aligning their crystals to allow light to pass through. In the absence of an electrical current, the liquid crystals are randomly aligned and appear as dark spots that form the numbers and letters that we see on an LCD display. LCD-based windows are already found in homes and offices around the world. With a flick of the switch, they turn from transparent to dark. These materials are used primarily in user-controllable privacy windows. The drawback to LCD-based devices is the lack of control over the darkness of the window. This problem is addressed in a new technology called a suspended particle device, which allows a window to change from dark to clear by applying an external electrical current. These devices are a sandwich of two glass panes coated with conductive material that hold a liquid suspension of particles. The particles align themselves when an external current is applied to the conductive glass coating, allowing light to pass through the glass. When the current is removed, the suspended particles move back to a random orientation to block light and darken the glass. Varying the applied voltage produces different shades of darkness for the glass.