Inputs
Add one or more glazing components. Use shading multipliers to represent blinds, fins, screens, or dirt effects.
Formula used
This tool estimates peak solar heat gain through glazing.
- Area (per component): A = width × height (or an area override).
- Weighted SHGC: SHGCw = Σ(Ai × SHGCi) ÷ ΣAi.
- Combined multiplier: M = Mexterior × Minternal × Mscreen × Mdirt.
- System SHGC: SHGCsys = SHGCw × M (clamped 0–1).
- Adjusted irradiance: Gadj = G × Forientation × Ftilt.
- Peak heat gain: Qpeak = SHGCsys × Atotal × Gadj.
- Energy estimate: Eday = (Qpeak × sunHours) ÷ 1000 (kWh/day).
- SC approximation: SC ≈ SHGCsys ÷ 0.87.
How to use this calculator
- Add each glazing component as a row (windows, curtain wall panels, skylights).
- Enter width/height (or provide an area override) and the component SHGC.
- Set irradiance and pick orientation/tilt to reflect the design condition.
- Apply multipliers for exterior shading, interior shading, screens, and dirt.
- Choose peak sun hours and days to estimate daily and period energy.
- Press Calculate to view results above the form, then export.
Note: Orientation/tilt factors are simplified; for compliance, use project-specific solar models.
Example data table
Sample glazing sets for quick validation and learning.
| Scenario | Area (m²) | Base SHGC | Exterior mult | Interior mult | Irradiance (W/m²) | System SHGC |
|---|---|---|---|---|---|---|
| Low‑E facade | 6.00 | 0.28 | 1.00 | 1.00 | 650 | 0.274 |
| Clear glass, blinds | 4.20 | 0.70 | 1.00 | 0.60 | 700 | 0.412 |
| Overhang + Low‑E | 5.50 | 0.32 | 0.75 | 1.00 | 750 | 0.235 |
| Skylight (tilted) | 2.00 | 0.45 | 0.85 | 1.00 | 800 | 0.375 |
| Screen + dirt | 3.80 | 0.40 | 1.00 | 1.00 | 680 | 0.376 |
Values are illustrative. Use manufacturer SHGC ratings and measured site assumptions for design decisions.