What is the Best Hot Tub Insulation?

Hot tub insulation can be confusing.  What is the best?  With a variety of hot tub insulation practices, many consumers find it overwhelming.  After all, every hot tub manufacturer claims to have the best insulation and have the lowest energy operating costs.  So what is really the best hot tub insulation?

All hot tub insulation is not created equal.  Typically, every hot tub is going to be insulated in two ways, the top (cover), and the sides (area between the shell and exterior of the spa.

Covers can range from 1.0 lb. and 2.0 in foam density. The higher the number, the better hot tub insulation it will offer. Most manufacturers use 2.0 lb core density, however, some less expensive spas will cut costs by lowering the foam density, as well as quality of vinyl and stitching. For a premium price, hard shell covers are a custom option and offer the best insulation, as well as longer life.

Hot tub insulation, which is used on the side of the spa, does vary, and often gets confusing. Below is a chart to help you understand that various insulations that are used, as well as a grade as to their effectiveness.


Type: No Insulation          Grade: F

Believe it or not, but there are spas that are manufactured without any insulation between the shell and exterior. They are rare, but they do exist. These spas are typically made inexpensively in China, and can often be found for sale on the internet and warehouse only sales. Don’t be fooled by words that say “insulated spa” but never mention what type of insulation is used. They may just be referring the the cover that it comes with. Spas with no hot tub insulation will result in higher energy cost, as well as potential problems with shell cracks as there is no support.


Type: Thermal Wrap or Blanket         Grade: D

This hot tub insulation practice consists of an insulation blanket being wrapped along the lining of the shell and/or inside exterior walls. There is a large void of space that is exposed. This hot tub insulation method is often compared to that of what is standard for insulating refrigerators.  What it fails to mention is that it is not used for insulation of industrial freezers. Instead full foam insulation is used for this application. It is not as energy efficient as other methods, and does not provide strength support for the shell, or the spa siding.


Type: Partial Urethane Foam Insulation       Grade: D

This hot tub insulation method is fairly common. A layer of foam insulation is sprayed on the inner lining of the shell. It provides about the same level of insulation as the thermal wrap, with one advantage.  The foam will add strength to the shell.   Often consumers misunderstand the specifications and mistake partial foams as being full foam.  You will know it is a partial foam application if  the word “full” is not used in the specs.


Type: Full Urethane Foam Insulation 2lb        Grade: C

This hot tub insulation is also commonly found in spas. This is a good insulation system.  Not only does it provide good hot tub insulation, but the support that it provides for both the shell and the plumbing will result in fewer leaks and a greater chance that the shell does not weaken and crack over time. Do not be worried by claims that plumbing repairs are more difficult and costly due to trying to work around the foam. Instead find comfort in the knowledge that your spa will experience far fewer plumbing leaks due to the added support that the lines have. The vibration of lines is most often what causes a leak, and spas with full foam experience 10 times fewer leaks that those without foam.


Type: FiberCor Insulation        Grade: B

Relatively new to the market, FiberCor is a great answer for consumers who have concerns with full foam and the potential of costly leak repairs. FiberCor has four times the density of the urethane foam used in most hot tubs. It’s a loose, wool-like fiber that fills all voids and gaps in our hot tub compartments for better insulating efficiency than any other hot tub. It is also very easy to remove, making future repairs easier then full foam.


Type: Multi Density and Multi Layered Full Urethane Foam        Grade: A

This is the best hot tub insulation you will find when it comes keeping the heat in and providing your spa shell and the equipment with the absolute best support against plumbing leaks and cracks in the shell. This system begins with a 60lb foam being shot onto the shell lining, making the shell stronger then others. It is then followed by multiple layers of foam of a variety of densities providing over all density that is greater then 2lb. Many consumers ask, why don’t other spas just use a 4lb or 6lb full foam to achieve better insulation, and it is is because of the foams expansion. The expansion of using a 2lb foam to fill the spa will not cause damage to the shell or exterior. However, if a spa is filled entirely with, lets say 4lb foam, it will expand and likely cause damage over time to the spa. Using a variety of density foam in multiple layers allows the foam to expand into each other, creating an all higher rating of density. Due to the increased cost of assembly time and assembly space needed to achieve this system, is not commonly used when manufacturing spas.


It is important to mention that finding a spa with the best hot tub insulation does not necessarily determine if a spa is going to to be energy efficient.  There are four other factors to take into consideration if you are trying to find the most energy efficient spa on the market.

  • Does the spa have a 24 circulation pump? If so, what is the wattage of this pump?
  • Does the spa ever turn on a jet pump for filtration purposes? If so, how often, for how long and what is the horsepower of the pump?
  • Does the spa every turn on a jet pump for heating purposes? If so, what is the average daily temperature of where you live, and what is the horsepower of the pump?
  • Does the spa reuse the heat generated in the equipment compartment to heat the spa, or does it release it outside?

If you are looking for a spa that will not cost a lot to operate each month look for one with the best hot tub insulation, a 24 hour circulation pump, one that never has to turn on a jet pump on for filtration or heating purposes, and one that reuses the heat generated in the equipment area. All of these combined will keep the costs down and you will be relaxing in your spa, instead of stressing out of the cost.  A portable spa can cost you as little as $10 a month to use regularly and to keep hot 24/7 to as much as $150 or more a month.  Important to know is that a spa costing $150 a month to operate will receive industry awards for energy efficiency and can be certified as an energy efficient spa because when compared to an in-ground being kept hot 24/7 using both gas and electrically, the cost to operate is significantly lower.

A common myth is that 110v vs. 220v electrical connections will consume more electricity and cost you more.  This is completely untrue.  The only advantage to a 220v electrical connection is that you can run both the jet pumps and heat the spa at the same time.  Depending upon your climate, or if you like extra long soaks, you may find the 220v to be a better choice.  I have personally owned both types and have never had a problem with heat loss.

At Coastal Spa & Patio, we have one of the largest display of spas, and feature many brands.  We have spas from entry level to luxury, and have something for any size backyard or budget.  Our spas also feature a wide variety of insulation applications and sales professionals can help you find not only the right tub, but the right insulation.  Come on in today and learn how we make “Backyard Living Better”.


3 responses to “What is the Best Hot Tub Insulation?

  1. Thanks for this article. I’ve just started looking and this explains a lot about insulation and cost effectiveness.

  2. I’m beginning to research hot tubs. I need one with good insulation an one with the highest pressure jets that I can get. My arthritis is getting bad an need it to help with my pain. I also need to keep the cost of operation as low as possible. Need good honest information.

    1. We carry a lot of brands, but the Hot Spring Spas, specifically the Highlife Series, is one of the best for energy efficiency thanks to the 7 layer insulation system. Check out their energy calculator at

      In this series, I would recommend either the Aria or Envoy. Both have amazing jet pressure and superior massage!

      I you are in the Southern California area, Coastal Spa and Patio of Placentia can definitely help you with your research. If not, check out the Hot Spring Spas website at https://www.hotspring.com

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