Numerous studies demonstrate that so much of our energy usage comes from the buildings we spend time in, whether they be our home, office, school, or other place. An ideal building, of course, will keep conditioned air (heated in the winter, cool air in the summer) in the building and minimize infiltration of non-conditioned air from the outside. There are many places in a building from which such an exchange can happen. With the exception of large openings, the most common place where air can be exchanged is at windows. Windows being transparent can also allow air to go through, and are much thinner than any walls. As one says in the field, “A bad wall is better insulation than a good window.” So a focus on any area to minimize air movement from inside to outside or vice versa is to strengthen the windows.
The problem with upgrading windows to minimize conditioned air loss is that new windows are expensive compared to the cost of electricity saved by using the air conditioner less in the summer or gas or oil saved by using a boiler less in the winter. Often building owners wait until there is a noticeable draft before upgrading windows; at that point the conditioned air effect is great. Because windows often have a long payback – often beyond what is “acceptable” at many companies – one idea is to create a hybrid project of window upgrades and LED lighting, whose payback is short. Together, they could yield an acceptable payback to upgrade windows before it is very late. If a company separates projects and only goes for short paybacks then window upgrades can take a great amount of time. Window film is a way to improve insulation properties somewhat fairly inexpensively without the capital cost or installation.
Recent research is trying to turn windows into not only better insulation for a building, but into electricity-generating items, too. Materials scientists have embedded light-absorbing films in window glass to keep heat out in the summer. But films can also be used to generate electricity; solar panels on windows. Such films, however, give windows a reddish or brown tint that building owners and architects find unappealing.
Newer solar window technology absorbs more invisible UV or IR radiation, leaving the glass clear while blocking the UV and IR radiation that can normally transfer through the window, resulting in unwanted heat in the building and raising the demand on the AC system. These new UV/IR absorbing windows can cut heat gain while generating electricity. For a glass building it could be possible that the building will power itself.
Research is also ongoing about a new class of opaque solar cell materials, called perovskites. They are improving in efficiency, approaching 22%, only a little behind standard crystalline silicon whose top efficiency is about 25%. Perovskites provides the interesting potential option that they can also be adjusted chemically to absorb specific frequencies of light if it is important to remove a certain frequency from the area or allow other frequencies to travel through.
CCES can help you assess the conditioned air losses in your building and recommend upgrading your windows or other ways to tighten your building and save energy usage, demand, and cost. Contact us today at 914-584-6720 or at karell@CCESworld.com.