Are you worried about heat in your homes? Did you know that over 25% of the heat from homes and public buildings escapes through the windows? No worries, Vitraz is here to provide you with Insulating glass units, or IGUs, which are designed to keep homes warmer in the winter and cooler in the summer. An insulating glass unit commonly consists of two (sometimes more) panes of glass separated by a spacer material and sealed together at the edge.