U-Value Calculator

Calculate thermal transmittance (U-value) from wall layer composition — insulation, concrete, air gaps — free energy efficiency tool

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Material Presets

Wall Layers (from interior)

Interior surface resistance Ri = 0.11 m²K/W | Exterior surface resistance Ro = 0.04 m²K/W

Layer 1

Material Name

Thickness (mm)

Conductivity λ (W/m·K)

Treat as air gap

Layer 2

Material Name

Thickness (mm)

Conductivity λ (W/m·K)

Treat as air gap

Layer 3

Material Name

Thickness (mm)

Conductivity λ (W/m·K)

Treat as air gap

Temperature Settings

Indoor Temp (°C)

Outdoor Temp (°C)

U-Value (Thermal Transmittance)

0.396 W/(m²·K)

R_total = 2.5228 m²K/W

Heat Flux: 7.93 W/m²

Layer-by-Layer Thermal Resistance

Layer	d (mm)	λ (W/m·K)	R (m²K/W)	Share
Interior Surface	-	-	0.1100	4.4%
Plasterboard	12.5	0.22	0.0568	2.3%
Glass Wool 16K	100	0.045	2.2222	88.1%
Concrete	150	1.6	0.0937	3.7%
Exterior Surface	-	-	0.0400	1.6%
Total	-	-	2.5228	100%

Temperature Gradient Through Wall

Indoor: 20°COutdoor: 0°C

Indoor Surface19.1°C

After Plasterboard18.7°C

After Glass Wool 16K1.1°C

After Concrete0.3°C

Formula

R_total = Ri + (d/lambda) + Ro

R_total = 0.11 + 2.3728 + 0.04 = 2.5228 m²K/W

U = 1 / R_total = 1 / 2.5228 = 0.396 W/(m²·K)