Reflective glass is glass that has been treated with a metallic coating
to allow it to reflect heat. It is not reflective in the sense that it
acts as a mirror, although some products do indeed have a highly
reflective surface, but rather in the sense that it reflects radiation
rather than absorbing it. This type of glass is used in environmentally
friendly construction with the goal of reducing heat gain and loss. Heat generated inside the building tends to stay in the building when
the windows are made from reflective glass, which reduces heating costs.
Conversely, heat from the outside stays outside, with the radiation
being bounced back by the glass. This keeps the building cool in summer.
Some structures that use it may be able to scale down or eliminate
their climate control systems and other passive measures.