Cold rooms are critical for food, pharma, and logistics industries, where even small temperature deviations can mean product loss or safety risks. The insulation panel is the backbone of cold storage, it defines how well the room resists external heat, stabilizes temperature, and minimizes energy costs.
In tropical climates, the challenge is even greater:
- High ambient temperatures (30–45 °C)
- High humidity levels causing condensation risks
- Intense solar loads on walls and roofs
This makes choosing the right insulation panels essential for performance and cost-efficiency.
Insulation Panel Types
1. PUF (Polyurethane Foam)
- Thermal conductivity (k): 0.022–0.024 W/m·K
- Most widely used for cold rooms in India and Asia.
- Excellent thermal resistance at economical cost.
- Example: For ice cream storage in tropical climates, 125 mm PUF with stainless steel (SS) inside and pre-coated galvanized iron (PCGI) outside is industry standard.
2. PIR (Polyisocyanurate)
- k: 0.021–0.023 W/m·K
- Slightly better thermal resistance than PUF.
- Superior fire resistance → preferred in pharma and food processing facilities.
3. EPS & XPS (Expanded/Extruded Polystyrene)
- k: 0.030–0.036 W/m·K
- Lower insulation efficiency compared to PUF/PIR.
- Often used in floors (because of high compressive strength) or in budget cold rooms.
4. VIP (Vacuum Insulated Panels)
- k: 0.004–0.006 W/m·K (10× better than PUF).
- Premium solution where space is limited (e.g., pharmaceutical transport boxes).
- High cost restricts use in large cold rooms.
Panel Construction Fundamentals
Insulation panels are sandwich panels with three key layers:
- Core Material (Insulation): PUF, PIR, EPS, or VIP.
- Internal Facing: Stainless steel or aluminum → food-grade, corrosion-resistant.
- External Facing: PCGI or aluminum → protects against weather, sunlight, and corrosion.
Key Considerations
- Food storage: SS is mandatory inside for hygiene.
- Outdoor exposure: PCGI or aluminum cladding to resist rust.
- Mechanical strength: Panel density ~40 kg/m³ for PUF/PIR ensures durability.
Selecting Thickness
The required thickness depends on target temperature and ambient conditions.
Formula 1: R-Value
R = ( t / k )
Where:
- t = thickness (m)
- k = thermal conductivity (W/m·K)
Formula 2: U-Value
U= 1 / R
Formula 3: Heat Gain Through Panels
Q=U×A×ΔT
here:
- A= surface area (m²)
- ΔT = temperature difference (°C)
Worked Example (includes SS skin, PCGI skin, films)
- PUF core: t= 0.125 m, k= 0.022 W/m K
- Inside skin (SS 304): t= 0.0005 m, k=15 W/m K
- Outside skin (PCGI): t=0.0005 m, k=50 W/m K
- Films (wall, still air): Rsi=0.13, Rse=0.04
Layer resistances
- RPUF=0.125/0.022=5.682 m² K / W
- RSS=0.0005/15=0.000033 m² K / W
- RPCGI=0.0005/50=0.000010 m² K / W
Total & U-value
Rtotal=0.13+0.000033+5.682+0.000010+0.04=5.852 m² K / W
=0.13+0.000033+5.682+0.000010+0.04=5.852 m² K / W
U = 1 / R total = (1 / 5.852 ) =0.171 W /m2 K
Calculating Envelope Heat Gain
Q = U x A x Delta T
Example : (wall area A=20 m², ΔT=35 °C from 40 °C ambient to −25 °C storage, U=0.171 W /m2 K ):
Q=0.171×20×35≈120 W
Sum all walls/ceiling/floor + doors + infiltration + product/people/process to size the system
Application-Specific Examples
Ice-Cream Storage (−25 °C to −30 °C)
- 125 mm PUF insulation
- Inside: Stainless Steel (hygiene, corrosion protection)
- Outside: PCGI
Blast Freezing (−35 °C to −40 °C)
- 150–200 mm PUF/PIR
- PIR preferred for fire safety
- Both sides SS facing to handle frequent wash-downs
Fruits & Vegetables (0 °C to +5 °C)
- 75–100 mm PUF
- Focus: humidity control → prevents wilting
- Inside: Food-grade SS or aluminum
- Outside: PCGI
Pharma Cold Rooms (+2 °C to +8 °C)
- 100–120 mm PIR panels
- Stainless steel facings for GMP compliance
- VIP optional in space-constrained facilities
Frozen Fish/Meat (−18 °C to −20 °C)
- 100–125 mm PUF
- Inside: Food-grade SS
- Outside: PCGI
ASHRAE & Energy Efficiency Perspective
While ASHRAE 90.1 primarily addresses commercial building envelopes, its principles apply to cold rooms:
- R-values and U-values guide panel selection.
- Continuous insulation prevents heat bridges.
- Vapor barriers stop condensation inside panels.
- Installation detailing (doors, floors, corners) is as important as insulation thickness.
Target U-values for cold rooms in tropical climates:
- Chilled storage (0 to +5 °C): U ≤ 0.3 W/m²·K
- Frozen storage (−20 °C to −30 °C): U ≤ 0.2 W/m²·K
- Blast freezers: U ≤ 0.15 W/m²·K
Installation & Practical Tips
- Airtight joints: Use tongue-and-groove or cam-lock joints.
- Avoid panel compression: Maintains designed R-value.
- Corner detailing: Prevents thermal bridges.
- Floor insulation: Often uses XPS for higher load capacity.
- Regular inspection: Panel seals degrade over time, increasing energy costs.
Conclusion
Choosing the right cold room insulation panels is not just about thermal performance but also about energy efficiency, hygiene, durability, and compliance with ASHRAE standards.
- Use PUF or PIR panels for most applications.
- Select thickness based on temperature requirements (75 mm for +5°C storage, 125 mm+ for frozen products, 150–200 mm for blast freezers).
- Ensure correct facings (SS, PCGI, Aluminum) based on hygiene and corrosion exposure.
- Don’t ignore installation details—thermal bridges can undo good design.
With the right insulation panels, facility managers and engineers can ensure product quality, lower operating costs, and long-term cold room performance.
