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Multi-Layer Wall Heat Transfer

🌡️ Energy & Fluids · Heat loss and U-value calculation via a convection + conduction thermal resistance network

🧮 Calculate∑ Formula✅ Verification📚 Sources

Inside temperature Ti (°C)

Outside temperature To (°C)

hi (W/m²K)

ho (W/m²K)

Layer 1 — thickness (mm)

k₁ (W/m·K)

Layer 2 — thickness (mm)

k₂ (W/m·K)

Layer 3 — thickness (mm)

k₃ (W/m·K)

Wall Area A (m²)

Total thermal resistance R0.1125 K/W

U value0.592 W/m²K

Heat loss q222.2 W

Heat loss per area q"14.81 W/m²

R = 1/(hi·A) + Σ Lᵢ/(kᵢ·A) + 1/(ho·A) · · q = ΔT / R

💡 Per TS 825, the target U for exterior walls varies by climate zone, roughly U ≈ 0.4–0.6 W/m²K. Set a layer's thickness to 0 to disable it.

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R = \frac{1}{h_i A} + \sum_i \frac{L_i}{k_i A} + \frac{1}{h_o A}

Heat loss calculation in buildings closely resembles the series-resistance logic of electrical circuits: heat traveling from the inner to the outer surface passes in turn through the inside convection resistance, each layer’s conduction resistance, and the outside convection resistance. Since these resistances are in series, they simply add up.

The U-value (overall heat transfer coefficient) summarizes a wall’s thermal insulation performance in a single number — a lower U-value indicates better insulation. In Turkey, the TS 825 standard defines target U-values that vary by climate zone; for typical exterior walls this value is roughly in the 0.4–0.6 W/m²K range.

Practical use: this tool supports up to three layers (e.g. brick + insulation + plaster). To analyze a wall with fewer layers, you can disable an unused layer by setting its thickness to 0.

✅ Verified

This tool's calculation logic has been checked against a hand-computed numerical verification test. Test source: src/lib/calc/isi.test.ts.

[3] Çengel, Yunus A. and Ghajar, Afshin J.. Heat and Mass Transfer: Fundamentals & Applications, 6 ed.. McGraw-Hill, 2020. ↗
[16] TSE. TS} 825 — Binalarda Isı Yalıtım Kuralları. Türk Standartları Enstitüsü. (TODO(oz): güncel baskı yılı doğrulanmalı) ↗

Multi-Layer Wall Heat Transfer — EngineersLab calc card

Formula: R = 1/(hi·A) + Σ Lᵢ/(kᵢ·A) + 1/(ho·A)

Sources: [3] Heat and Mass Transfer: Fundamentals & Applications; [16] TS} 825 — Binalarda Isı Yalıtım Kuralları

Tool version: 1.0.0 · Date:

Source URL: https://engineerslab.com.tr/en/araclar/isi

Results are for educational and preliminary-sizing purposes; final engineering design decisions must reference the relevant standards and a licensed engineer's approval.