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<p>Amid rising urban temperatures and deteriorating indoor environments, ensuring thermal comfort in existing residential buildings has become an urgent challenge, particularly in hot-humid regions like Karachi. This study explores how strategic retrofitting of building envelopes can transform thermal conditions in older dwellings. A single-story house in the Malir District was digitally modeled in Autodesk Revit and simulated in Design Builder using Energy-Plus. The Predicted Mean Vote (PMV) model, aligned with ASHRAE Standard 55, was employed to quantify comfort levels. Annual simulations of the base case revealed severe discomfort, with summer PMV reaching approximately + 2.73 and winter PMV remaining as high as + 1.28, confirming overheating as the dominant comfort challenge and prompting targeted analysis for the month of May. A series of insulation materials, like polystyrene, polyurethane, fiberglass, elastospray, and cork, were applied to the roof and wall envelopes. The results demonstrated that all insulation materials improved indoor thermal comfort; however, cork consistently outperformed others, maintaining PMV values closest to the ideal range. Roof-only insulation proved most effective, with cork reducing PMV to approximately + 1.36, a nearly 50% improvement over the base case, while elastospray, polystyrene, and polyurethane offered more modest gains. Wall-only insulation produced smaller improvements, with best at a PMV of approximately + 1.6, underscoring the dominant contribution of roof heat gain in Karachi's climate. Combined roof-and-wall insulation yielded the most substantial results: cork insulation lowered PMV to approximately + 0.46 in May, a reduction of over 80% from the base case, and sustained near-neutral comfort year-round. Sensitivity analysis further showed that roof insulation alone contributed most of the improvement, offering a practical solution for cost-sensitive retrofits. These findings underscore the transformative potential of simple envelopes upgrades in achieving sustainable, comfortable, and resilient urban housing.</p>

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Simulation-based evaluation of building envelope retrofitting for enhanced thermal comfort in hot-humid climates: a case study of Karachi

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月29日

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  • Warda Fatima,
  • Asghar Abbas,
  • Hammad Haider,
  • Muhammad Haider,
  • Hussain Ali

摘要

Amid rising urban temperatures and deteriorating indoor environments, ensuring thermal comfort in existing residential buildings has become an urgent challenge, particularly in hot-humid regions like Karachi. This study explores how strategic retrofitting of building envelopes can transform thermal conditions in older dwellings. A single-story house in the Malir District was digitally modeled in Autodesk Revit and simulated in Design Builder using Energy-Plus. The Predicted Mean Vote (PMV) model, aligned with ASHRAE Standard 55, was employed to quantify comfort levels. Annual simulations of the base case revealed severe discomfort, with summer PMV reaching approximately + 2.73 and winter PMV remaining as high as + 1.28, confirming overheating as the dominant comfort challenge and prompting targeted analysis for the month of May. A series of insulation materials, like polystyrene, polyurethane, fiberglass, elastospray, and cork, were applied to the roof and wall envelopes. The results demonstrated that all insulation materials improved indoor thermal comfort; however, cork consistently outperformed others, maintaining PMV values closest to the ideal range. Roof-only insulation proved most effective, with cork reducing PMV to approximately + 1.36, a nearly 50% improvement over the base case, while elastospray, polystyrene, and polyurethane offered more modest gains. Wall-only insulation produced smaller improvements, with best at a PMV of approximately + 1.6, underscoring the dominant contribution of roof heat gain in Karachi's climate. Combined roof-and-wall insulation yielded the most substantial results: cork insulation lowered PMV to approximately + 0.46 in May, a reduction of over 80% from the base case, and sustained near-neutral comfort year-round. Sensitivity analysis further showed that roof insulation alone contributed most of the improvement, offering a practical solution for cost-sensitive retrofits. These findings underscore the transformative potential of simple envelopes upgrades in achieving sustainable, comfortable, and resilient urban housing.