Structural heating is a major source of energy consumption in many countries. Yet a lot of this heat is lost through windows as float glass is an effective heat conductor. Using gas to insulate windows cuts the amount of heat loss, saves energy and reduces noise levels. Mono-atomic and rare gases are ideal for insulation and can be fed in between double or triple panes of glass. Argon and krypton are the most commonly used gases and gas mixtures here. They are also often used for noise insulation in busy areas (such as airports or along rail lines or roads) due to their optimum density.