Air handling unit (HJU) wall panels are typically made of double-layered colored steel plates or cold-rolled steel plates with powder coating (sometimes the inner side of the bottom plate is made of stainless steel). The insulation material in between is mostly polyurethane foam or flame-retardant centrifugal glass wool. From the perspective of thermal conductivity, water absorption, and density alone, both are good insulation materials. However, during operation, the supply and return air fans run at high speeds, causing significant vibration within the unit. Glass wool, being lightweight and having large gaps in its structure, is prone to shedding due to prolonged vibration, leading to a sharp increase in thermal conductivity and loss of insulation effectiveness. This results in condensation on the HJU wall panels, causing the supply air temperature to be too high.
However, the use of polyurethane foam does not guarantee good insulation performance. Inferior polyurethane foam insulation materials can also affect the performance. Therefore, the choice of wall panel insulation material should not be made lightly when selecting an HJU.
