WinterGuard® waterproofing shingle underlayment is the solution for winning the battle against water penetration in your roof's most vulnerable places. WinterGuard is a composite material of asphalt polymers, formed into a rolled sheet. The asphalt makes it vapor-tight, and the polymers make the asphalt elastic and sticky. This protective barrier is able to stretch and seal around nails driven through it. WinterGuard is one of the key components in the CertainTeed Integrity Roof System® which is comprised of underlayments, shingles, accessory products and ventilation all working together. The Integrity Roof System is designed to provide optimum performance--no matter the weather conditions.