Windows, which can be defined as holes in the sides of buildings through which energy enters and escapes, are one of the most important battlegrounds in the struggle to increase efficiency.

This is true for a couple of reasons. On one hand, windows perhaps are the element of the building where the barrier between the outside and inside environment is thinnest and where it is most important to control the entry and exit heating and cooling. On the other, the sheer amount of glass in a typical structure represents a golden opportunity to harvest solar energy.

There are several ongoing projects aimed at improving performance and leveraging windows. “I see that there is going to be a change in how glass is put into buildings and how it will function,” said John Conklin, the President and CEO of SolarWindow. “I see an increase in competition by integrators — companies that take PV technology and integrate into building PV. I see that is going to be a booming business.”

SolarWindow is a technology that collects energy from the window and enters it into the building’s energy infrastructure. Conklin said the technology – which will become commercialized next year – uses a thin and almost invisible coating of conductive organic material. “We collect energy at the surface of the window,” Conklin said. “Through our technology – which includes what we call ‘invisible wires,’ we move the electricity into wires [adjacent to the window] and into the building system.”

The system, Conklin said, is configured differently depending on whether it is a new construction, a broad retrofit project or a window replacement. The windows, he said, have the potential to cut building energy use in glass-intensive sky scrapers between 30 percent and 50 percent and have a payback on investment of less than one year.

There is lot going on in windows. Last month, Energy Manager Today posted a story post about window film which The International Window Film Association (IWFA) claims can stop as much as 85 percent of solar energy from entering the building and retain 55 percent of energy – in the form of heating and cooling – from escaping.

The news was that that its Window Film Savings Calculator had been approved by the California Energy Commission as a way to determine the value of window film installations and enable schools in the state to apply for funding under Proposition 39. This enables standalone window film projects; previously, window filming only was done during broader retrofits.

The split seems to be between passive and active windows. Technavio Research Analytst Soumya Mutsuddi told Energy Manager Today in February that there are two types of smart glass: Electrically activated and environmentally activated. Each category can be further segregated into subgroups. SolarWindow and window film sector fit into the passive window category which, the analyst told Energy Manager Today, can be subdivided into photo-chromatic, thermo-chromatic and thermo-tropic categories. The bottom line is that there are a lot of approaches to creating windows that use sophisticated technology to drive energy efficiency.

Earlier this year, Lawrence Berkeley National Laboratory’s website posted a story about research into a paint-like substance that be applied to existing windows to reflect heat. One of the researchers told the reporter that the polymer would enable visible light to pass through the window while reflecting infrared frequencies. The team is working under a $3.95 million award from the Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E) at the University of Colorado Boulder. Caltech and Materia Inc. also are participating in the project.

There are other projects and companies working on – or already offering – products. The sense is that they range from relatively inexpensive add-ons to existing windows to expensive, wired window that react to the physical environment inside the structure on a real time basis. The bottom line is that there are many smart and entrepreneurial people in the glass business.

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