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Keywords

Thermal Resistance, degree-day analysis, sensitivity analysis, multi-layer wall, conductive heat transfer; building envelope

Document Type

Research Article

Abstract

This study develops a multiscale analytical framework to quantify how thermal conductivity changes in fly-ash-modified recycled fine aggregate concrete (FA-RFAC) transfer to wall and climate-response scales. Five conductivity scenarios (0.60–1.40 W/(m·K)) were evaluated using a standardised multi-layer reference wall, and transfer was quantified using local transfer elasticity and a finite-change thermal-performance retention factor. The resulting wall U-values were combined with heating and cooling degree-days for Beijing, Shanghai, and Guangzhou. The local transfer elasticity was mathematically equivalent to the fraction of total wall resistance provided by the FA-RFAC layer. At the reference conductivity of 1.00 W/(m·K), FA-RFAC and rock wool contributed 12.4% and 75.6% of total wall resistance, respectively. Reducing FA-RFAC conductivity to 0.60 W/(m·K) produced a 40% material-level reduction but only a 7.64% reduction in wall U-value, from 0.6202 to 0.5728 W/(m²·K), with a retention factor of 0.1555. The annual transmission index decreased by 3.17, 1.98, and 0.78 kWh/(m²·year) in Beijing, Shanghai, and Guangzhou, respectively, while the relative reduction remained 7.64%. Thus, wall resistance distribution governs relative transfer, whereas climate determines its absolute annual significance.

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Publication Date

30-9-2026

First Page

1

Last Page

16

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