New materials and design elements
Modern hot tubs achieve their overall efficiency using a combination of design elements, including:
Insulation
Everyone understands the need for insulation; most homes built today have adequate insulation and meet the requirements and guidelines of California Energy Code (Title 24), The Energy Efficiency Standards for Residential and Non-residential Buildings. However, not thought about as often are the plethora of appliances consumers have in their home and the insulation systems they use.
From the wall-mounted oven or dishwasher to the side-by-side refrigerator, insulation either keeps the heat in or out. In fact, most people are surprised to learn that modern hot tubs use the same basic techniques and materials of a typical refrigerator.
Although many new insulation systems are now available to the hot tub industry—from urethane foam (used in high-efficiency refrigerators) to reflective foils (used in aerospace technology)—the goal is the same—keeping heat in the water. Energy efficiency comes at a price, however. Effective insulation systems cost more than minimal insulation, and a better insulated cover costs more than a thin cover. Therefore, it is better to pay for these efficiencies up front, rather than paying more down the road in higher operating costs.
Many hot tubs are sprayed with polyurethane foam, which fills any voids in and around the plumbing (i.e. full foam). The foam is available in a variety of densities as it not only insulates the plumbing and hot tub shell, but also doubles as structural support for the flex tubing used in most plumbing designs. This is the most widely used system in the industry as it has the best performance history.
Another insulation technique involves using a rigid sheet of polyurethane foam comprising a reflective surface to capture the warm air on the inside of the hot tub. This helps prevent heat loss by creating a barrier to capture heat from the pump and keep it in the area created by the rigid foam panel and back of the hot tub shell. One advantage of these systems is the plumbing remains exposed for easy accessibility.
Some manufacturers also use standard batted fibreglass insulation in and around equipment areas to help protect the plumbing from freezing. This insulation, commonly found in the walls of most homes, is effective as well as easy to use and replace if it becomes damaged.
Reinforcement systems
One area not so apparent to consumers, but still important, is the reinforcement system. This is what gives the hot tub shell its strength. While fibreglass is still popular, there are new materials that are more environmentally friendly. For example, many manufacturers are now using new high-density polyurethane materials for shell reinforcement. This material does not contain any volatile organic compounds (VOCs) and is much safer for the manufacturing environment.
It can also be applied using automation processes (e.g. robots) instead of physical labour. The one downfall of this material, however, is its cost as it is more expensive than fibreglass.
