Andersen’s 400 Series replacement windows are consistent best-sellers and are a favorite among contractors. Additionally, they’re more energy-efficient than the 100 Series, which means they can save you more on your monthly heating and cooling costs. Material in the 400 Series Windows Andersen’s 400 Series windows have elegant wood interiors and rugged Perma-Shield exteriors. Andersen formulated Perma-Shield in 1966 to merge the beauty of wood with durable, weather-resistant vinyl. Thanks to their strong Perma-Shield exterior and solid wood interior construction, 400 Series windows are resilient enough to last for many years. They’re also low-maintenance, with exteriors that never require painting.