For even greater energy savings, choose Revere windows with the BarrierXP® insulated glass package. BarrierXP combines multi-layer low-emissivity (Low-E) glass and argon gas, along with the PPG Intercept® Warm-Edge Spacer System, to achieve outstanding energy savings. Many BarrierXP glass packages meet the latest ENERGY STAR® requirements. Consult your window professional for the optimal glass package required for your home and climate area.