Hi Pros,
Everywhere I shop, I see that spa covers are made with EPS foam. What the heck is that?
Hannah from Philadelphia Pennsylvania
Hello Hannah from Philly!
The foam core in hot tub covers is typically made from expanded polystyrene or EPS. EPS is a tough and rigid closed-cell foam. This is important as the closed-cell foam retards water absorption and helps the top to last as long as possible.
The EPS starts the process as very, very small beads. The beads are placed into molds and heated with steam so they expand and take on the shape of the mold. The temperature must exceed 100 degrees Celsius for this process to occur. These beads can expand to 100 times their original size. This illustration shows the scale of these small beads.
EPS beads
The video below explains the entire process of how these beads become sheets of EPS for use in spa covers.
EPS sheets can be made with different densities of foam. The greater the density, the stronger the foam will be. Greater densites of foam are made by starting the process with greater amounts of the small beads in the mold. If the amount of beads is increased, and they are allowed to expand to only the same size of mold, each bead can expand less therefor making the final product be comprised of more dense foam.
Foam densites are typically discussed in the amount of pounds. For example, hot tub lids typically come in 1.0, 1.5 or 2.0 pound densities. This means each foam can withstand that many pounds of pressure per square inch.
Foam density is only a small part of the overall insulating ability of the foam core. Increasing the foam density is the primary component that determines the cover strength, or how much wet, melting snow it can hold before it cracks or breaks.
This link will take you to a handy R-value calculator, to see the difference the foam density makes.
Happy Tubbing!
Ethel Elliott
