GreenGuard Attic Rafter Vents comprise closed-cell extruded polystyrene (XPS) that is thermoformed to a shape that, when installed between roof rafters, allows air to flow from the soffit to the attic space. GreenGuard Attic Rafter Vents allow continued air-flow to keep attics cooler in hot weather and help reduce moisture condensation in the attic during cold weather. GreenGuard Attic Rafter Vents help optimize performance of attic insulation by minimizing wind washing, prevent blown insulation from blocking the air-flow, keep the space between soffit vents and attic space open during construction and maintain air channels over time.