Polyurethane sandwich panels (PIR/PUR sandwich panels) have become the ideal choice for cold storage construction due to their outstanding thermal insulation and fire resistance properties, eco-friendly characteristics, and significant energy-saving and efficiency advantages. Selecting the appropriate thickness is a critical prerequisite for achieving efficient and stable cold storage operation.

So, how do you choose the right PIR sandwich panels for your project? Today, let's explore the answer together!

01 How to Calculate Sheet Thickness

According to the description of insulation materials for cold storage facilities in GB 50072-2021 Cold Storage Design Standard: “When lightweight composite sandwich panels, such as metal-faced insulated sandwich panels, are used for thermal insulation and thermal barrier enclosures in cold storage warehouses, the combustion performance of the sandwich panel core material shall not be lower than Class B1. Furthermore, the Class B1 core material shall be a thermosetting material.”

According to GB 50072-2021 Cold Storage Design Standard, the thickness of thermal insulation materials for building envelopes shall be calculated using the following formula:

In the formula:

d: Thickness of thermal insulation material (m)

λ: Thermal conductivity of thermal insulation material [W/(m·℃)]

R0: Total thermal resistance of the building envelope (m²·℃/W)

aw: Heat transfer coefficient of the exterior surface of the building envelope [W/(m²·°C)]

an: Heat transfer coefficient of the interior surface of the building envelope [W/(m²·°C)]

di: Thickness of the i-th layer of material in the building envelope excluding the thermal insulation layer (m)

λi: Thermal conductivity of the i-th layer of material in the building envelope excluding the thermal insulation layer [W/(m·°C)]

Thermal Conductivity: Also known as thermal conductivity, it represents the amount of heat transferred per unit area (1 m²) per unit time when a material layer has a temperature difference of 1 K (or 1°C) across its two sides and a thickness of 1 m under steady-state heat transfer conditions. Thermal conductivity is a physical quantity that measures a material's ability to conduct heat and is an inherent thermal property of the material.

Heat Transfer Coefficient: Also known as the convective heat transfer coefficient, it represents the amount of heat transferred per unit area (1 m²) per unit time during convective heat exchange when the temperature difference between the fluid and the solid surface is 1 K (or 1°C). This coefficient directly reflects the heat exchange capability between the fluid and the solid surface. Unlike thermal conductivity (which describes heat transfer within a material), it specifically addresses heat exchange at the fluid-solid interface.

Thermal resistance: Represents the temperature difference required across an object to transfer 1W of heat. Thermal resistance quantifies an object's or material's ability to impede heat transfer, analogous to electrical resistance (which impedes current flow).

02 Application Demonstration

Consider the following scenario: A steel-framed prefabricated cold storage facility exists in a certain location. Its exterior walls and roof utilize single-layer profiled steel sheets, while polyurethane sandwich panels serve as insulation for interior walls and ceilings. The following data is provided: The average outdoor air conditioning temperature during summer is 30°C, and the operational temperature inside the facility is -18°C. Calculate the required thickness of polyurethane sandwich panels for the ceiling and wall panels.

Polyurethane corrected thermal conductivity coefficient:

Wall Thermal Differential Correction:

Total Thermal Resistance of Wall Surface:

Wall Insulation Material Thickness Calculation:

Wall insulation thickness must not be less than 149mm. Therefore, 150mm thick polyurethane sandwich panels can be selected for wall insulation.

Ceiling Thermal Differential Correction:

Total thermal resistance value for suspended ceilings:

Calculation of suspended ceiling insulation material thickness:

The ceiling insulation thickness must not be less than 160mm. Therefore, 180mm thick polyurethane sandwich panels can be selected for ceiling insulation.

03 Low thermal conductivity, greater energy efficiency

To achieve superior thermal insulation in cold storage facilities and deliver highly efficient, energy-saving solutions, WISKIND and BASF jointly introduce an innovative flagship product: low thermal conductivity polyurethane cold storage panels.

To clearly illustrate the differences between standard polyurethane insulation panels and low thermal conductivity polyurethane cold storage panels, the following table recommends thickness selections for both products under identical environmental conditions.

Notes:

· This table provides ideal calculations based solely on the specific requirements of the aforementioned scenario;

· Actual projects should be calculated specifically according to local conditions and the environment surrounding the cold storage facility;

· This table does not differentiate between walls and ceilings, using the component with higher thermal resistance in identical scenarios for calculation;

· This table excludes floor and partition wall thickness calculations and does not account for additional insulation materials (rock wool, glass wool, brick walls, etc.).

Low-Thermal-Conductivity Polyurethane Cold Storage Panels: Breakthrough technology achieves an ultra-low thermal conductivity of 0.017–0.019 W/m·K, enhancing insulation performance by 20% and improving cold storage operational efficiency. Compared to traditional insulation panels, this product significantly reduces energy consumption by 10%–15% annually for equivalent panel thickness and building area.