The most commonly used material is steel because it's strong and economical. However, if your grille is located in a humid place — such as next to a sauna, swimming pool, or in a bathroom — plastic or aluminum materials are the common materials used. Plastic, however, is at a disadvantage as it lacks strength and can discolor over time. Your best bet for areas with high humidity is aluminum. HVAC Premium has a wide range of aluminum grilles, from Cubic Core to perforated — you can view our selection here.To find out more about our aluminum Cube Core grilles, click here.