Early-Stage Thermal Risk Diagnosis in High-Altitude Andean Residential Buildings: An Exploratory Envelope-Based Alert Matrix and Post-Simulation Discomfort Ratio

High-altitude Andean climates present dual thermal pressure: daytime overheating risk coexists with nighttime heat loss within the same annual cycle. Aggregate energy indicators do not reveal the direction of thermal discomfort, limiting their utility for early-stage passive design. This study proposes a two-stage exploratory diagnostic framework for residential buildings in this context. Stage 1 uses window-to-wall ratio (WWR) and average opaque wall thermal transmittance (U-wall) to construct a preliminary thermal-risk alert matrix that is applicable at the schematic design phase. Stage 2 uses the post-simulation Discomfort Ratio (DR = Href/Hcal) to confirm the direction of thermal discomfort as overheating-dominant, heat-loss-dominant, or mixed. The framework was applied to 14 anonymized residential building energy simulation cases in Loja, Ecuador. Of 13 classifiable cases, DR assigned 5 to overheating-dominant, 5 to heat-loss-dominant, and 3 to mixed patterns; 6 cases with complete WWR and U-wall data populated the Stage 1 matrix. The surface-to-volume ratio and air changes per hour did not clearly discriminate across patterns. The framework is exploratory and corpus-specific; the alert matrix does not replace dynamic simulation and requires validation before normative or predictive application. Alongside DR, a bounded directional-intensity index (Normalized Discomfort Balance) and the total discomfort load are reported so that the direction and the magnitude of discomfort can be read jointly.