Use Q = U × A × ΔT for each wall, ceiling and floor surface.

In short: different surfaces may have different U-values and temperatures on the other side, so calculate them separately.

Example: 10 m² at U 0.22 W/(m²K) and ΔT 25 K gives 55 W. This excludes doors, bridges and leaks.

The formula

Q_transmission = U × A × ΔT

U = panel U-value (W/m²·K) — lower is better; set by panel thickness and core conductivity
A = total external surface area (m²) — all six faces
ΔT = temperature difference between outside and inside (K)

Worked example

A room of 4 m × 3 m × 2.5 m built with 100 mm panels (U ≈ 0.22 W/m²·K), holding 0 °C in a 25 °C plant.

Surface area A = 2(4×3) + 2(4×2.5) + 2(3×2.5) = 24 + 20 + 15 = 59 m²
ΔT = 25 − 0 = 25 K
Q_transmission = 0.22 × 59 × 25 = 324 W

A thicker panel lowers U and cuts this load directly — the same room in 80 mm panels (U ≈ 0.28) would transmit ~410 W.

Frostbox standard range: Frostbox/Algor panels are 80 mm and 100 mm for chill rooms and 100 and 120 mm for freezers — pick the thickness for your target temperature, not from a generic thickness chart. The 80 mm "without floor" option exists for chill rooms only.

Reducing transmission load

Thicker panels lower U-value for the whole surface, the most direct lever.
Smaller surface area (compact geometry) reduces A.
Lower ΔT — siting a room away from a hot plant or rooftop ambient reduces the driving temperature difference.

See Panel specifications and Insulation science for how U-value is derived from panel thickness and core conductivity.

For a checked calculation, use the Frostbox size calculator or contact [email protected].

The formula

Worked example

Reducing transmission load

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