Is selenium a building material?
No. Although it is a useful nonmetal, it is not used in general building construction except as an additive to glass.
The biggest use of selenium is as an additive to glass. Some selenium compounds decolourise glass, while others give a deep red colour. Selenium can also be used to reduce the transmission of sunlight in architectural glass, giving it a bronze tint. Selenium is used to make pigments for ceramics, paint and plastics.
Selenium has both a photovoltaic action (converts light to electricity) and a photoconductive action (electrical resistance decreases with increased illumination). It is therefore useful in photocells, solar cells and photocopiers. It can also convert AC electricity to DC electricity, so is extensively used in rectifiers. http://www.rsc.org/periodic-table/element/34/selenium
Selenium is a mineral found in the soil. Selenium naturally appears in water and some foods. While people only need a very small amount, selenium plays a key role in the metabolism. Selenium has attracted attention because of its antioxidant properties.
Antioxidants protect cells from damage. Evidence that selenium supplements may reduce the odds of prostate cancer has been mixed, but most studies suggest there is no real benefit. Selenium does not seem to affect the risk of colorectal or lung cancer. But beware: selenium also seems to increase the risk of non-melanoma skin cancer.
Among healthy people in the U.S., selenium deficiencies are uncommon. But some health conditions -- such as HIV, Crohn's disease, and others -- are associated with low selenium levels. People who are fed intravenously are also at risk for low selenium. Doctors sometimes suggest that people with these conditions use selenium supplements http://www.webmd.com/a-to-z-guides/supplement-guide-selenium#1