Solar Gain — House Thermal Study

Temperatures above, solar production below, on the same clock. Watch the attic trace the sun with a lag.

Positive means the attic is a radiator sitting on the ceiling. The evening tail is stored heat, not sun.

Decision: not worth it — too much install effort for a modeled 3.5–8°F peak cut and little tail relief, with an insulation top-up already planned. Card kept as the record. Model: attic ≈ outdoor + a + b·solar (exponentially smoothed); barrier removes 25% (15–35%) of the solar-driven excess. Hottest day in range.

Same fitted model, different physics: venting raises the attic's heat-loss conductance, which divides both the solar gain and the flush time. Central estimate doubles the conductance (band: +50% to +150%) — a full ridge + opened-soffit retrofit, not a ridge vent alone; the wind analysis below suggests intake is currently the bottleneck. Hottest day in range.

An unconditioned room acts as the test instrument (the best-fitting room without an AC): its temperature is fitted against outdoor air and the attic delta, then replayed with the ceiling coupling cut to R-38 (from an assumed R-12 today, band R-10 to R-15). The same fitted attic-coupling share scales the measured AC energy. Simplification: insulation also slows heat arrival, which this ignores — real relief is slightly better than shown. Hottest day in range.

Each dot is a 10-minute interval with meaningful solar heat in the attic: how much hotter or cooler the attic ran than solar alone predicts (y) vs wind speed (x). A downward trend means wind is moving air through the vents; flat means the tucked-under-the-eaves intake is the bottleneck. Full dataset, ignores the range filter. Suggestive, not proof — wind and time of day travel together.

Each room (green) against outdoor and attic context (gray). Shared temperature scale. Blue bands mark that room's AC running (kitchen shares the living room unit; bedroom bands are power-derived from the Emporia outlets).