Heat naturally moves from a warmer area to a colder one. A thick layer of rigid foam slows that movement.
In short: the PUR core limits conduction, while sealed joints stop warm, humid air leaking between panels.
The metal skins are strong and easy to clean but conduct heat well. Most insulation comes from the foam core. Increasing the core thickness usually improves thermal resistance, although the final result also depends on joints, doors and penetrations.
Closed cells in PUR trap gas and prevent it circulating freely. This gives the foam low thermal conductivity. A typical engineering value may be around 0.022–0.024 W/(m·K), but design calculations must use the current manufacturer data.
Even good insulation cannot compensate for a door left open or a poorly sealed pipe hole. Treat the enclosure as one continuous thermal and air barrier.
The panel fights heat on three paths
The refrigeration system can only pump heat out so fast. If heat floods in faster than the unit can remove it, the room loses temperature. The insulated panels exist to slow that flood to a trickle, and they fight heat on all three transfer paths at once.
| Mechanism | How heat moves | How the panel stops it |
|---|---|---|
| Conduction | Through solid material | A rigid closed-cell foam core traps gas in millions of sealed pockets; gas conducts heat poorly |
| Convection | Carried by moving air | Cam-lock joints under mechanical tension seal the gaps, so no air circulates between inside and out |
| Radiation | Electromagnetic waves | The metal skins reflect radiant heat |
The dominant factor is the thickness and quality of the foam core. Frostbox/MTH Algor panels use a rigid polyurethane (PUR) core between two steel skins, joined by an embedded cam-lock mechanism — covered in detail in Panel specifications and What is a cam-lock cold room?.
Understanding R-value
R-value measures thermal resistance — how strongly a panel resists heat flow. Higher is better. A typical PUR core (thermal conductivity λ ≈ 0.022–0.024 W/m·K, a generic PUR figure rather than a quoted MTH/Algor spec) delivers far more resistance per millimetre than conventional building materials, which is why a thin cold-room panel out-insulates a thick masonry wall:
- PUR foam (≈40 kg/m³): very high R per mm — the reason cold-room walls are slim
- Fibreglass batt: roughly half of PUR's resistance for the same thickness (λ ≈ 0.040–0.044 vs ≈ 0.022–0.024 W/m·K)
- Solid brick: 25–30× worse per millimetre — you would need a wall roughly 2.5–3 m thick to match a 100 mm PUR panel
Doubling the core thickness roughly doubles the thermal resistance, so stepping from a chiller panel to a freezer panel materially cuts the heat the unit has to fight. How target temperature sets that thickness is covered in How temperature sets panel thickness.
Related articles
- How Cold Rooms Work
- How temperature sets panel thickness
- The refrigeration cycle explained
- What is a cam-lock cold room?
- Panel specifications
Recommendations reflect the MTH Algor panel system supplied by Frostbox. For help specifying a panel for your application, contact [email protected].
