Are There Any Paint-On Window Energy Glazes?

Smart Coating

• Semiconductor nanocrystals may give your windows a way to save you money on your electric bill. A heat-smart coating would allow the sun's heat in when wanted, and block it when keeping the room cool is desired. Today, commercial buildings have windows with reflective coatings that can block near-infrared light and the heat it produces. Unfortunately, the coating does not allow heat in when it is cold out. Don't expect to be able to buy spray-on coatings or heat-smart windows anytime soon. The new coatings have been successfully tested in the laboratory. Now the next step is to develop and test window prototypes.

Spray-on Solar

• Spraying nanocrystals or working solar cells onto window glass represents a giant leap forward in solar technology. Some estimates cite increased efficiency vs. roof-installed solar panels, plus much lower costs of materials and installation. Homeowners love lots of windows, especially big ones, but rising energy prices have made them less attractive. When windows with solar cells that dramatically reduce utility bills are available, the attitude could change to "the more big windows the better." The process for producing nanoparticles that contain marketable photovoltaic solar cells is still being developed. Residential products will not be available until at least 2016, but commercial windows may be available earlier.

Driving Solar

• Car manufacturers are testing the idea of spraying automobiles--windows, body and all- with solar cell coatings. Expectations are that a car could travel 6 miles on two hours of sun exposure. Although efficiency lags current electric cars, solar power from coatings represents a no cost alternative. Some auto makers are already planning to produce prototype vehicles.

Choices Today

• Today consumers' choices for reducing energy bills with windows are limited to selecting insulated windows or window film. Although insulated windows are not new, current models can save 50% of the energy loss that a single pane window allows. Low-emittance coatings on windows allow them to gain or repel heat depending on the coating selected. Consumers need to choose the right model for their climate zone and most manufacturers offer product recommendations based on where you live. Window film is less versatile than insulated windows. It is designed to either keep heat from escaping or to reflect light and heat, keeping interiors cooler. Consider your location and the direction windows face when choosing film. Homeowners in the southern United States might apply reflective film to south- facing windows while northerners could use heat absorbing film on north-facing windows.