Rigid PU foam for hot water tank and boiler insulation

Residential boilers, electric water heaters (traditional and tankless), solar water heaters with tank, heat pumps for water heating, and industrial hot water tanks use rigid PU foam injected in the space between the internal reservoir (stainless or glass-lined steel) and the external casing. The foam performs both thermal and structural functions: minimizes heat loss by conduction and supports the tank within the external shell.

Typical systems use polyether polyol + MDI with HFO blowing agent (replacing HFC, which is being phased out globally). Density typically between 35 and 45 kg/m³, thermal conductivity 0.020-0.023 W/m·K. Thickness between 40 and 80 mm depending on target energy efficiency level.

Injection is performed in a closed mold with the tank inside — PU expands and fills all cavities. Any fill failure or void creates a hot spot that degrades product performance over time.