U-value (thermal transmittance) is the rate of heat transfer through a structure per unit area per degree of temperature difference. Lower U = better insulation. Units: W/(m²·K). U = 1/R_total.

How is wall heat loss calculated?

Q = U × A × ΔT, where Q is heat flow (W), U is thermal transmittance (W/m²K), A is wall area (m²), and ΔT is temperature difference between inside and outside.

R-value is thermal resistance: R = thickness/conductivity for each layer. Total R = R_si + ΣR_layers + R_se (including surface film resistances). U = 1/R_total. Higher R = better insulation.

What are typical wall U-values?

Uninsulated brick wall: U ≈ 2.0 W/m²K. Insulated cavity wall: U ≈ 0.3-0.5 W/m²K. Well-insulated wall (modern code): U ≈ 0.15-0.25 W/m²K. Passive house: U < 0.15 W/m²K.

What are surface film resistances?

R_si (internal surface) ≈ 0.13 m²K/W and R_se (external surface) ≈ 0.04 m²K/W account for the thin boundary layer of still air at each surface. They are included in the total thermal resistance calculation.

मुक्त अभियांत्रिकी साधन

भिंती मधून उष्णता नुकसान कॅल्क्युलेटर

संयुक्त भिंतींमधून होणारा उष्णता तोटा Q = U × A × ΔT मोजा. साहित्याचे थर जोडा, तापमान सेट करा आणि U-value व उष्णता प्रवाह मिळवा.

Q = U·A·ΔTबहु-स्तरीय#176

Results

उष्णता तोटा Q

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U-Value

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एकूण R-Value

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उष्णता फ्लक्स q

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संयुक्त भिंतीतील उष्णता हस्तांतरण

R_si = 0.13 m²K/W (आतील पृष्ठभाग), R_se = 0.04 m²K/W (बाह्य पृष्ठभाग).

Heat Loss Through Wall Calculator | Free U-Value Tool

Published by Nikolai Shelkovenko on फेब्रुवारी 15, 2026 एप्रिल 5, 2026

Results

संयुक्त भिंतीतील उष्णता हस्तांतरण

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