Thermal Performance of Pitched-Roof Attic Configurations Under Varying Roof Insulation Levels in Rural Dwellings

Pitched-roof attics are common in Chinese rural dwellings, but how their comfort and energy benefits vary with roof insulation remains to be quantified. This study used an EnergyPlus model of a traditional U-shaped dwelling in Hanzhong to compare paired Attic and No-attic configurations at roof U-values of 2.7, 1.5, 1.0, 0.6, and 0.3 W/(m2·K). Free-running simulations evaluated the annual percentage of comfortable hours (PCH), hourly indoor temperatures, and attic daily temperature range (DTR) attenuation; conditioned simulations evaluated equivalent electricity consumption for heating and cooling. Attic achieved higher annual PCH and lower heating and cooling consumption in all scenarios. As U-value decreased from 2.7 to 0.3 W/(m2·K), the PCH increment decreased from 1.632 to 0.160 percentage points and the combined energy-saving rate from 19.55% to 11.26%, whereas attic DTR attenuation increased from −18.95% to 61.14%. Stronger insulation narrowed bedroom temperature differences, but Attic had a peak temperature approximately 0.460 °C higher in bedroom A during the hottest week at U = 0.3 W/(m2·K). Roof insulation thus improved overall performance while reducing the annual incremental benefits of the Attic configuration. Reduced attic temperature fluctuations did not necessarily coincide with lower local summer peaks. Roof insulation and attic configuration should be designed jointly to balance annual comfort, energy use, and extreme temperatures.