Thermal and Indoor Air Quality Trade-offs in Southeast Asian Apartments During Power Outages: A Coupled Simulation Study for Property Due Diligence and Retrofit Planning

An apartment may have air conditioning and a portable air cleaner yet lose essential environmental services when electricity or mechanical cooling is interrupted. Opening a window can dilute occupant-generated carbon dioxide while admitting outdoor heat or smoke. This computational working paper examines those competing effects and their implications for apartment purchases, long-term tenancies, and building upgrades in Southeast Asia. The study couples a two-node resistance-capacitance heat model with well-mixed balances for fine particulate matter and carbon dioxide. Its numerical programme comprises 432 factorial 24-hour cases, 1,024 sensitivity evaluations, ten cleaning-energy cases, and 27 continuous 72-hour cases. A stationary analysis identifies conditions under which ventilation requirements for heat and carbon dioxide conflict with the limit imposed by outdoor particle entry. All apartment parameters and environmental sequences are explicitly specified as constructed inputs. Regional research from Bangkok, Phnom Penh, Jakarta, Surabaya, and Singapore provides context for the physical mechanisms and property questions examined. Official haze and electricity-reliability sources help distinguish regional environmental exposure from assumptions about individual buildings. These sources do not calibrate the simulated apartments or establish the frequency of the modeled conditions. The results show why a single window-opening rule can struggle to satisfy several environmental objectives. In the reference case, filtration with carbon-dioxide purging reduces particle concentration and carbon-dioxide accumulation, while peak modeled air temperature remains above the selected temperature screen. A matched analysis of 144 masonry–shaded pairs finds peak-temperature reductions of 0.73–1.98°C, with a median reduction of 1.62°C. Small carbon-dioxide increases in 17 pairs demonstrate how reduced cooling demand can alter temperature-responsive window operation. The property analysis translates these mechanisms into evidence requirements for solar exposure, usable airflow paths, façade alteration permissions, delivered filtration, backup circuit coverage, and shared cooled spaces. It distinguishes installed equipment from services demonstrably available during an interruption. The 85-page paper contains 25 numbered equations, 16 figures, 13 tables, and 27 references. An embedded reproducibility archive supplies executable code, model inputs, computed results, matched comparisons, and a source catalogue. The study does not estimate property-price premiums, regional outcome frequencies, or safe occupancy durations; its simulations require physical validation before building-specific application. AI-use disclosure: AI assistance contributed to research framing, model and code development, analysis, source synthesis, and manuscript preparation. Numerical results were generated by executing the supplied code. This version is presented as a computational working paper for substantive author review.