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Home > Spa Cover - Foam density
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This illustration shows a hot tub covers foam core on top with 1.0 pound foam
over a hot tub cover foam core on the bottom with 2.0 pound foam. |
HOT TUB COVERS & SPA COVERS: FOAM DENSITY
Hot tub covers are made with a core of foam. The foam gives hot tub covers the majority of their strength and insulation from the foam cores deep inside the hot tub covers. The foam density, typically shown as 1.0 pound, 1.5 pound or 2.0 pound, is one of the most over rated hot tub cover components, as we will discuss here.
First, a definition is in order. The foam density is a measure of the amount of foam in a given space. For example, a block of foam that is a six inch cube, with length, width and height all being six inches, can have varying foam densities. No matter what foam density is used, the cube will always remain the same in every dimension.
Foam sheets are made by pouring the "beads" into a four foot by eight foot form. The amount of beads put will determine the density the sheet will become. For 1.0 pound foam cores, one pound of foam "beads" are put into the form for every square foot of form space. Next, pressurized steam is forced into the form, causing each of the beads to "pop" and swell to fill the form. Each bead will swell to its maximum size depending on the number of beads and the remaining size of the form.
Hot tub covers need the foam cores to be both strong and to have low absorption properties. It is easy to understand that more foam in the form will produce a more dense, stronger foam sheet and eventually hot tub covers.
Myth #1 - Hot tub covers with more dense foam absorb less water
An advertised benefit of a more dense foam core in hot tub covers, is that the more dense foams have less air space between each bead where water can be absorbed. While this is true in reality their still remains sufficient capillary action that will let hot tub covers water log and weigh hundreds of pounds.
The age old saying is "A pound of prevention is worth an ounce of cure". It is a much better consumer value to spend on prevention of water logging with upgraded vapor barriers, than to spend for higher density foam to try to minimize air spaces inside the foam once water is in.
Myth #2 - Hot tub covers with more dense foam are stronger
Another advertised benefit of more dense foam is to add strength to hot tub covers. It is true that a 2.0 pound foam core will be stronger than a 1.0 pound core if they are of the same thickness. However, 1.0 pound foam core hot tub covers that are thicker will be stronger than 2.0 pound hot tub covers that are thinner. The better value for the consumer is to spend for increased thickness before spending for increased foam density.
If you think of the insulation in the attic space of a house (the pink stuff), you gain more home insulation if you add thickness to the insulation, not by smashing additional rolls of insulation into the same sized space.
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