Hot tub insulation  keeps heat in the tub and reduces demands on the system’s various heating components. Hot tub insulation comes in a few different forms, some more efficient at heat retention than others.

Depending on the insulation material and density in your hot tub, you could experience greater comfort, lower utility bills and longer-lasting components … or the opposite.

The most common types of hot tub insulation are:

  • A hot tub cover
  • No insulation
  • Thermal wrap
  • Partial foam
  • Full foam
  • FiberCorⓇ
  • Multi-density foam

Here we’ll talk about the above common forms of hot tub insulation and how they perform when it comes to heat retention.

The Hot Tub Cover

A hot tub cover  is the most important form of insulation you can use. Because heat rises and water evaporates, the cover provides  a barrier that keeps both heat and water in the tub rather than out in the air.

hot tub cover

Ideally, your cover will be designed for your specific spa model and slightly higher in the center than on the edges (discouraging puddles of water on top). Look for one with high density foam and a skirt that will cover the edge of the acrylic shell.

Extend the life of your hot tub cover by properly caring for and cleaning  it. Eventually, the cover will get waterlogged from steam and evaporation, and it won’t offer much in terms of insulation. At that point it’s time to get a new one.

No Insulation

Hot tubs are generally made of an acrylic shell that sits within a square cabinet. Less expensive types may even be inflatable. In both cases, a great deal of air exists between the seats and exterior.

If that area isn’t insulated, the heat will quickly move out into that airspace, lowering the temperature of your water.

While hot tubs with shells and cabinets are typically insulated to some degree, inflatable hot tubs generally aren’t. Be wary of such products that claim to be insulated but probably aren’t.

Thermal Wrap

Think of this like a large blanket that wraps around the underside of the inner shell or the inside of the outer cabinet. In some cases, a thermal wrap is applied to both places for extra insulation.

Some thermal wraps use a reflective material that reflects some heat back toward the hot tub shell. They may also be used along with partial foam (see next section) for additional insulation.

While a thermal wrap is certainly better than no insulation, it’s not going to provide very effective insulation for a hot tub. It’s more appropriate for swim spas , which are kept at lower temperatures.

Partial Foam

This kind of hot tub insulation is common. The foam may be in the form of boards or a spray-on material. Spray-on foam has the added benefit of adding some support to the underside of the shell.

Partial foam insulation keeps hot tubs more affordable. For consumers looking to enjoy a hot tub that will remain in moderate temperatures, this could be a perfect way to balance efficiency and affordability.

Partial foam insulation does leave a significant amount of air within the cabinet. The cabinet is not airtight, which means that some heat will still be lost to the outside.

Full Foam

Full foam insulation is the same spray-on material used in partial foam hot tub insulation. The difference is that foam fills the entire area under the shell and inside the cabinet, encapsulating the shell, plumbing and heating components.

Full foam benefits are clear. Obviously you’ll enjoy better heat retention and energy efficiency. The shell will also be better supported. In addition, the foam will protect the plumbing and heating components from movement and vibration, reducing the chance for leaks and breaks.

Full foam hot tub insulation is significantly more expensive than partial foam. Of course, with saved energy, the cost could be well worth it in the long run.


FiberCorⓇ is a relatively new type of hot tub insulation, and is only available with certain brands at the moment. However, the material it uses may become more common in the future.

Like full foam, FiberCor fills the entire cavity between the shell and the cabinet exterior. Rather than being sprayed-on, the wool-like fiber is blown into the space through a tube connected to a machine.

It has quadruple the density of foam for excellent heat retention. It’s also relatively easy to remove if needed.

Multi-Density Foam

The foam hot tub insulation used in partial and full foam jobs comes in a range of densities. While denser foam provides more insulation, it also has less space for expansion.

Full foam hot tubs cannot use the highest density foam because the expansion would damage the tub. However, using foams of multiple densities, and layering them in the cavity, means you get the greatest insulation with no risk of expansion damage.

Multi-density insulation costs more than other types because it is labor intensive to install. Of course, it also provides the best level of support and efficiency, and will save you money when it comes to heating and repairs.

The best insulation is going to cost you more up front, and certain types may not be easy to find. However, it will save you money in the long run.

Consider your needs for efficiency and budget, and contact your local Aqua Living dealer with any questions.