Inputs
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Enter inputs and click Calculate to see recommendations.
Example data
Click Load to fill the form with the row’s values.
| City | Latitude (°) | Date | Time | H (m) | Exposure |
|---|
Formulas used
Solar geometry (simplified):
- Day of year:
nfrom selected date. - Declination:
δ = 23.45° · sin( (360° · (284 + n)) / 365 ) - Hour angle:
h = 15° · (Tsolar − 12) - Solar altitude:
α = asin( sinφ·sinδ + cosφ·cosδ·cosh ) - Overhang to fully shade height
Hat altitudeα:Lshade = H / tanα
Rain/wind exposure rule‑of‑thumb minimums (eaves): Low 200 mm, Moderate 300 mm, High 450 mm.
How to use
- Select your measurement units.
- Enter site latitude, date, and local solar time.
- Enter the vertical height to shade beneath the eave.
- Choose the rain/wind exposure category.
- Press Calculate to see shade and minimum overhangs.
- Export your results using CSV or PDF.
FAQs
It uses a simplified declination formula and solar altitude at a single time. For critical designs, simulate across dates/times or use professional solar tools.
For a horizontal eave shading a vertical wall, required projection depends primarily on solar altitude, not azimuth. Orientation affects how often shading is needed.
Common practice sets gable overhang near 50–70% of the eave overhang. This tool suggests 60% with practical bounds for typical houses.
Wind‑driven rain and storms increase splash and wetting. The category adds a minimum overhang to help push driplines farther from walls.
No. It gives conceptual recommendations only. Always confirm with local building codes, climate data, and professional detailing requirements.
Climate-based overhang suggestions
Indicative ranges for typical detached homes. Always confirm with local practice.
| Climate | Suggested eave overhang | Suggested gable overhang | Notes |
|---|---|---|---|
| Hot-dry | 450–600 mm | 300–450 mm | Prioritize shade; reduce glazing heat gains. |
| Warm-humid | 450–750 mm | 300–500 mm | Reduce wind-driven rain; protect openings and walls. |
| Temperate | 300–450 mm | 200–300 mm | Balance sun control and daylight access. |
| Cold | 200–300 mm | 150–200 mm | Limit snow load; allow winter sun penetration. |
Solar altitude quick reference
Overhang for full shade of height H equals H / tan(α). Ratios and examples for H = 1.20 m:
| Solar altitude α (deg) | Ratio Lshade/H | Example Lshade for H=1.20 m |
|---|---|---|
| 20° | 2.747 | 3.296 m (≈3296 mm) |
| 30° | 1.732 | 2.078 m (≈2078 mm) |
| 40° | 1.192 | 1.430 m (≈1430 mm) |
| 50° | 0.839 | 1.007 m (≈1007 mm) |
| 60° | 0.577 | 0.693 m (≈693 mm) |