Wood has been a traditional material of choice for cold storage door manufacturers, mostly because of its low cost and availability. However, because it is in a high moisture environment wood will have a tendency to warp, swell, and rot. Not only does this create numerous problems for maintaining a good perimeter seal, but these conditions encourage wood to harbor bacteria, mold, and fungus. Pressure treated wood solved the rotting problem for a while, but unfortunately it warps even more than untreated wood.
Fiberglass has some tremendous advantages in cold storage applications. Fiberglass is well known to be as strong as steel but 30 percent lighter in weight which helps in the operation of the door. It is impervious to water and moisture so it will never swell or rot and it is easy to clean. It also maintains its shape over a wide range of temperature differentials and will maintain all of its properties even in extremely cold conditions. Plus it offers extremely low thermal conductivity.