Here's how Sherwood windows work for you to save energy. First, Sherwood products are designed with performance in mind. Sherwood uses the highest quality PVC Vinyl and energy efficient multi-chambered designs from Veka, a world leader in the window industry. Sherwood windows meet industry performance standards set forth by independent agencies like the American Architectural Manufacturers' Association (AAMA) and the National Fenestration Ratings Council (NFRC).