Find Your Ideal Hot Tub: Spa Insulation
INSULATION
There are many different techniques for spa insulation. To evaluate how manufacturers insulate their spas, it is important to understand that spas lose heat through radiation, convection, and conduction. Choosing a spa that minimises heat loss will ensure the highest energy efficiency.
Heat Loss in Spas:
3-7% Conduction: Heat energy is transferred directly through materials in contact with each other where a temperature difference exists. Heat transfer along a metal rod is a simple example of conduction.
Up to 45% Convection: When air is heated, it becomes less dense than the surrounding air and rises upwards. Cooler, denser air flows downwards, creating convection currents.
50-75% Radiation: Heat energy radiates across air spaces and is then absorbed by another body. An example of this is radiant energy from the sun, which is absorbed as heat by the human body.
To achieve maximum efficiency, hot tubs should be designed to minimise heat loss from all three sources.
ThermoLock Insulation
ThermoLock Insulation is a modern, energy-efficient method that uses minimal kilowatt energy to heat the water while also allowing easy access to spa plumbing for maintenance. This method incorporates a perimeter insulation blanket on the inside of the spa cladding to block conduction heat loss. Additionally, it traps heat generated by the pump motor, with the heated air helping to warm the spa water and reducing heat loss through convection.
ThermoLock insulation materials include spray foam, Styrofoam, and high-performance natural fibres. The best insulation is:
Mould-resistant
Insect-resistant
Easily removable and replaceable to its original condition
Backed by a strong insulation warranty
Note: Since radiation is a major source of heat loss, perimeter insulation must include a thermal reflector (such as a survival blanket) to radiate heat back into the spa plumbing and water.
Foam Fill Insulation
Foam fill insulation was traditionally used in most spas. This method involves completely filling the spa enclosure with spray foam and directly venting out the heat from the pump. While this is less expensive to construct, it is the least energy-efficient method of insulation and makes servicing difficult.
Most manufacturers have transitioned to the more energy-efficient ThermoLock method. However, some still use foam fill, which does not minimise heat loss from radiation or convection and offers poor overall energy efficiency.
Challenges with Foam Fill Insulation:
Servicing plumbing is difficult and costly.
Spas often need to be returned to the factory to remove and respray foam insulation with specialised equipment.
On-location repairs require lifting the spa, digging out foam, and using cans of spray foam, which typically fail to match the quality of factory-applied foam.
