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The "Lifeline" of Cold Storage Insulation: A Comprehensive Guide to PU Panel Jointing and Sealing Construction Standards

2026-05-08

In cold storage construction, the jointing and sealing of polyurethane (PU) panels are critical factors determining the success or failure of thermal insulation. An untreated 2mm gap can result in cooling loss of up to 15%. Based on the Code for Design of Cold Storage (GB50072-2021) and industry construction standards, this article systematically outlines the full-process technical requirements for PU panels, from material selection and jointing to sealing.

 

 
 
 
 

Material Selection First: Core Parameters of PU Panels

Polyurethane panels have become the preferred insulation material for cold storage due to their exceptional thermal performance. When rigid polyurethane density is 35–40kg/m³, the thermal conductivity is only 0.018–0.024W/(m·K), approximately half that of EPS foam board—the lowest among all insulation materials currently available.

According to the Code for Design of Cold Storage and the Sichuan Province Agricultural Product Cold Chain Construction Technical Plan, PU panels must meet the following core parameters:
Thickness Requirements: ≥100mm for -18℃ refrigerated storage, ≥150mm for deep frozen storage below -25℃
Density Standard: 40±2kg/m³
Flame Retardant Rating: Class B1 (self-extinguishing within 3–5 seconds after flame removal)
Color Steel Sheet Thickness: ≥0.426mm, double-sided spray-coated or stainless steel

Thermal Conductivity: ≤0.023W/(m·K)

 

Jointing Process: The "Art of Engagement" with Tongue-and-Groove and Eccentric Hooks

1. Standard Jointing Method

General cold storage panels employ a tongue-and-groove structure, with panels connected via internal eccentric hook lock boxes. This "one panel locks two panels" design not only facilitates installation but also ensures structural strength and durability. The eccentric hook core is made of steel, and hook box quality directly impacts the firmness and sealing of panel connections.

The standard panel width is 960mm, with length customized according to actual requirements. During installation, panel gap clearance must be controlled within 1.5mm—experimental data shows that an untreated 2mm gap can cause cooling loss of up to 15%.

2. Special Structure Handling

Controlled atmosphere storage, due to higher airtightness requirements, adopts a flat structure with panels connected via profiled sheets and polyurethane foam filling in between.

Ceiling panel installation employs round steel hangers connected to C-channel steel, with panels joined via eccentric hook lock boxes and reserved polyurethane foam filling space. After all ceiling panels are positioned, the reserved channels are filled with on-site polyurethane foam and covered with 0.7mm galvanized spray-coated sheets.

 

 

Sealing Construction: Three Lines of Defense Against Thermal Bridging

First Line: Polyurethane Foam Filling

Butt joint gaps between panels must be filled with polyurethane foam agent, with the foam overflowing approximately 1cm beyond the panel gap before being scraped flat. This "protective layer" can block 90% of cold air penetration. For junctions between wall panels and ceiling panels, and between wall panels and floor panels, a 50mm–100mm gap should be reserved and filled with on-site polyurethane foam.

Second Line: Sealant Closure

The exterior of panel gaps must be filled with neutral silicone sealant or polyurethane sealant, with sealant width ≥5mm, requiring continuous and uniform application. After all panel-to-panel connections are completed, a "two-coat-one-fabric" process (airtight sealant + non-woven fabric) is used for airtight treatment.

Third Line: Aluminum Foil Tape Reinforcement

The inner and outer surfaces of panel gaps can be sealed with aluminum foil adhesive tape to further enhance airtightness. For special areas such as internal and external corners, external corners are wrapped with metal corner guards, while internal corners require insulation panels cut at 45-degree bevels to ensure no cold leakage dead zones.

 

Critical Nodes: Airtight Treatment at Wall-Floor-Ceiling Junctions

The three most vulnerable areas for thermal bridging in cold storage—wall-to-floor, wall-to-ceiling, and panel-to-panel junctions—require specialized sealing measures:

Wall Panel to Floor Junction: The floor insulation layer should maintain a 50mm–100mm gap from wall panels, filled with on-site polyurethane foam; gaps between wall panels and the interior floor are sealed with aluminum foil mastic. Low-temperature storage floors also require heating wires, covered with a 2mm floor protection layer before insulation is laid.

Wall Panel to Ceiling Panel Junction: A 50mm gap is reserved during jointing, filled with on-site polyurethane foam after ceiling panels are positioned. The interior side is connected with ┓-type iron sheet internal corner pieces, fixed with rivets; the exterior side is sealed with specialized sealant.

Door and Window Opening Treatment: After cutting openings in panels, edges are wrapped with profiled sheets, then doors or windows are installed, followed by sealant application. Door frames and structures must be thermal-bridge-free, and low-temperature storage doors require built-in electric heating devices to prevent seal freezing.

 

 
 

 Airtightness Testing: The "Hard Indicator" for Acceptance

After construction completion, rigorous airtightness testing must be conducted. According to SB/T 11081 standards and the Sichuan Province cold chain construction technical plan:
Overall Airtightness Index: Air exchange rate ≤1.5 times/hour
Pressure Differential Method: At a test pressure of 196Pa, the half-pressure decay time must be no less than 10 minutes
Infrared Thermal Imaging: Detection of thermal bridges and cold leakage points

Any areas failing inspection must be reworked until standards are met before commissioning.


Construction Precautions
Substrate Preparation: Floor levelness error ≤3mm/m, wall verticality error ≤5mm; wall moisture content controlled below 9%
Continuous Construction: Insulation layers must be laid continuously in one operation; if interrupted for more than 2 hours, interface sealing must be re-inspected
Handle with Care: Avoid bumping or damaging panels during transport; protective film should be removed promptly after installation (no later than 2 months after purchase)
Prohibit Angle Grinders: Panel cutting should use fine-toothed saw blades to avoid damaging coatings

Rust Prevention: All C-channel steel and metal components require two coats of anti-rust primer

 


Conclusion

The jointing and sealing of polyurethane panels exemplify the engineering principle that "details determine success or failure" in cold storage construction. From controlling panel gaps to 1.5mm, to constructing three lines of sealing defense, to the 196Pa airtightness acceptance test, every step directly impacts the energy consumption level and service life of the cold storage. As industry experts often say: "80% of a cold storage's insulation performance depends on construction quality, and only 20% on the material itself." Only by strictly adhering to jointing and sealing construction standards can we truly build the "Great Wall of Insulation" for cold storage facilities.

 


 



 

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