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Spas are wonderful. Big electric bills are not. Insulation is one of the most important aspects to consider when purchasing a hot tub. It is the part of the hot tub's design and construction that will most determine the cost of operation. Imagine two hot tubs identical in size, holding the same amount of water, located in the same backyard, used identically, but that have dramatically different operating costs. How could one of these hot tubs cost as little as $15 per month to operate, while the other exceeds $100 per month? The difference is due to the method and type of insulation. No matter what type of insulation is used, as long as some form or method is employed, it will assist in reducing the operating cost of the spa.By incorporating insulation into the spa structure, the manufacturer is reducing the time it takes for the water temperature to pass from the body of water to the outside environment. By effectively doing so, the time that it takes to heat and maintain water temperature is reduced and in return, the cost to heat is also reduced. With the ever-increasing consumption of power in America and the rising cost of energy, a well-insulated unit, designed to eliminate heat loss and drive down operational cost, will save the consumer money. Understanding the benefits and differences between each type of insulation will help you choose the right hot tub and will save you money. Over 95% of spa manufacturers utilize one of the three types of insulation as explained below.


Basic insulation consists of a single, thin layer of polyurethane that is applied to the understructure of the spa shell. The biggest benefit to using basic insulation is the cost. Many mass merchants and entry-level spa manufacturers incorporate this type of insulation to reduce the overall cost of the spa.
Basic insulation is a suitable method of insulation for indoor spas. However, it does not provide an adequate insulating value for outdoor use, nor does it provide any soundproofing benefits. In most outdoor installations, basic insulation will not be sufficient. As a result your hot tub will be very expensive to heat, especially in the winter.


Full foam insulation consists of filling the area between the shell and cabinet sub floor completely with a thick layer of solid, rigid foam. Over 70% of hot tubs manufactured today use this method of insulation because it is an excellent way to insulate and support the hot tub shell. Full foam insulation will keep heating costs to a minimum whether you use the spa indoors or out. While some spas feature full foam insulation, it is often a low-density, open-cell packaging type foam which doesn't provide an adequate amount of insulation, and can result in expensive heating costs. However, multi-layers of high-density, closed-cell polyurethane foam (typically the same material used to insulate commercial freezers), result in low operating costs. "Closed cell" foam generally provides greater efficiency because it cannot absorb water. Here's a tip: Knock on the outside of the spa should produce a solid, sturdy sound, and not a hollow sound.

Also, be sure to ask the dealer or manufacturer for a documented estimated monthly operating cost. Multiply the average monthly power usage by the electricity cost quoted by your power company to estimate the impact a spa will have on your energy bill.

Along with the insulation advantages of urethane, noise cancellation from fully foamed spas is a valuable advantage to the end user. In addition, there is the added rigidity and structural aid that is given to the spa due to the attachment of the spa shell to the spa exterior during the filling process.


Layered insulation is the method of installing layers of insulating material between the cabinet walls and the spa shell, and is commonly referred to as "blanket insulation". When considering spas with layered insulation, look for materials that have high insulating values. Ideally, choose a manufacturer who uses multiple layers of insulation. A spa designed with removable walls will allow you to easily move the layers of insulation aside when the spa requires any type of service. This makes finding the problem simple with little time required to correct the problem, thus greatly reducing repair costs. If you desire to buy a layered insulated spa, beware that many manufacturers try to cut corners. The use of an inexpensive, single layer of insulation with no insulation along the base can result in very expensive heating bills. The ideal method is to have multiple layers of a high R-Value insulating material on all four interior cabinet walls, as well as a full layer of insulation along the base of the cabinet. This provides the best of all worlds - it does not prohibit the ability to service the spa and is an excellent method of insulation. In addition, if the material utilized has good soundproofing qualities, it will also help your spa to operate quietly.


Each type of insulation has their benefits and drawbacks, but the final decision is up to you. When making your decision, take into consideration these important factors: the location of your spa (indoors vs. outdoors); if the spa will be outdoors, the average outdoor temperature; built-in energy saving features that may be available on your hot tub; and the quality of your hot tub cover. Each of these factors will help determine the cost of operation of your spa, and will influence the effectiveness of the type of insulation that you choose. Just remember that once you have your hot tub, it is impossible to change its method of insulation.

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