1. Overview
The insulation layer is a critical structural component for achieving energy‑efficient operation of heated pools, especially in indoor constant‑temperature pools. Its performance directly affects operating energy consumption and user comfort. Proper material selection and standardised installation can effectively reduce heat loss from the pool water and extend the service life of the pool.
2. Comparison of Common Insulation Materials
Common insulation materials for swimming pools include XPS boards, rock wool with water repellent, and spray polyurethane rigid foam (SPF). Their performance characteristics differ:
| Comparison Item | XPS Board | Rock Wool + Water Repellent | Spray Polyurethane (SPF) |
|---|---|---|---|
| Thermal conductivity | Moderate | Higher | λ = 0.022 W/(m·K), lowest |
| Water resistance | Good | Fair | Closed‑cell ratio ≥92%, water absorption ≤3% |
| Construction adaptability | Requires cutting and jointing | Complex construction | On‑site spraying, adapts to curved surfaces |
| Thermal bridge issues | Joints create thermal bridges | Thermal bridges present | Seamless adhesion, eliminates thermal bridges |
Overall, although spray polyurethane rigid foam has a slightly higher initial cost (about 8% more), the energy savings over its full life cycle can recover the extra cost within 3.2 years, making it the preferred option for swimming pool insulation.
3. Spray Polyurethane Insulation Installation Procedure
Substrate preparation: The pool surface must be thoroughly cleaned to remove dust, grease, and loose particles before spraying.
Environmental control: Spraying should be carried out when relative humidity is below 75% and ambient temperature is above 15 °C. The optimum ambient temperature is 15–35 °C.
Layer‑by‑layer spraying: Polyurethane rigid foam is applied in multiple thin layers. Each pass should be about 15 mm thick. A working section may be completed with several passes, and work on the same day must be continuous without interruption.
Composite system construction: A composite system of "spray polyurethane rigid foam + anti‑crack mortar + chlorosulphonated polyethylene waterproof coating" is recommended. After the polyurethane insulation is sprayed, a bonding mortar and then an anti‑crack mortar shall be applied successively as protective layers.
Quality acceptance: After insulation installation, the thickness, closed‑cell ratio, and bond strength must be measured to ensure that the thermal transmittance meets the design requirement (e.g., K ≤ 0.35 W/(m²·K)).
4. Selection Recommendations
When choosing an insulation material, factors such as pool type (indoor/outdoor), required water temperature, budget, and design life should be considered. For indoor constant‑temperature pools, the spray polyurethane rigid foam system is strongly recommended for its superior overall performance.
