A 3-layer garage door is a type of garage door that consists of three layers: an outer layer, an inner layer, and a layer of insulation in between. These doors are also known as triple-layer garage doors or sandwich doors.

The outer layer of a 3-layer garage door is typically made of steel or aluminum. Steel doors are more durable and offer better protection against weather and impact, while aluminum doors are lightweight and corrosion-resistant.

The insulation layer in a 3-layer garage door can be made of various materials such as polystyrene, polyurethane, or other types of foam. Insulated garage doors help regulate the temperature inside the garage, making it more energy-efficient and comfortable. The insulation also helps reduce noise from outside, making the garage a quieter space.