This window solar heat gain calculator estimates the peak cooling load through glazing. Enter window area, SHGC, orientation, latitude, month, exterior and interior shading factors, the window U-value, and the outdoor-to-indoor temperature difference; the tool returns the solar gain, the conduction gain, the total, and the peak solar heat gain factor it used, plus an orientation comparison chart.
Windows are often the single largest peak cooling load in a perimeter space, and orientation drives it strongly. Seeing the solar and conduction components separately helps you weigh glazing selection, shading, and orientation early in design.
| Quantity | Equation |
|---|---|
| Solar gain | Q‑solar = Area × SHGC × SHGF × SC‑ext × SC‑int |
| Conduction gain | Q‑cond = Area × U × ΔT |
| Total window gain | Q‑total = Q‑solar + Q‑cond |
| Month adjustment | SHGF × month factor (Jul = 1.0) |
The peak solar heat gain factor (SHGF) values are from ASHRAE Handbook of Fundamentals Table 26 by orientation and latitude (July baseline, with month factors for June and August). SHGC is the glazing solar transmittance, and the exterior and interior shading coefficients further reduce the gain. Conduction through the glass uses the standard U × A × ΔT relationship. The result is a peak-hour estimate, not an hour-by-hour profile.