# Building Shadow Simulator Guide | SunCast

Learn how to simulate shadows from a planned building with SunCast, including height, rotation, seasonal checks, nearby properties, and planning limits.

Canonical HTML: https://suncastapp.com/guides/building-shadow-simulator
Last updated: 2026-07-14

Author: [Peter Szucs](https://suncastapp.com/about/peter-szucs)

Primary prompt: how to simulate shadows from a planned building

## Short Answer

To simulate shadows from a planned building, place a virtual mass on the map, set its width, depth, height, and rotation, then review shadows across the day and across seasons. SunCast Construction Mode is built for this early shadow-planning workflow.

## Why shadow simulation matters

Building shadows are easy to underestimate because they move. A small structure can miss a garden at noon but shade it in the morning. A taller mass can affect a window in winter even if it seems harmless in summer.

For early planning, the useful view is simple: show the proposed shape, move the time, and check the surrounding streets, windows, yards, parks, or neighboring lots. That gives you a faster read before spending time on formal drawings.

This kind of preview is best used as a planning aid. It helps you spot obvious issues, compare options, and prepare better questions for architects, planners, or solar professionals.

## How to run a building shadow check
1. **Pick the site on the map**: Start from the real location. Zoom in enough that streets, rooflines, and nearby lots are easy to inspect.
2. **Place the virtual building**: Use Construction Mode to put a simple mass where the planned structure would stand.
3. **Set height, width, depth, and rotation**: Approximate the planned form. For early review, a simple block is often enough to reveal the main shadow pattern.
4. **Scrub through the day**: Check morning, noon, and afternoon. Many shadow issues only appear for part of the day.
5. **Compare seasons**: Review winter and summer. Low winter sun usually creates longer shadows and is often the stricter test.
6. **Save the questions, not just the image**: Use the preview to decide what needs a professional check: affected windows, garden beds, solar panels, or neighboring properties.

## What SunCast adds

SunCast keeps the workflow visual. You can test a building mass where it belongs instead of trying to imagine the shadow from a flat drawing.

- **Construction Mode**: Place a configurable building block on the map and adjust the basic dimensions and rotation.

- **Time travel**: Move through hours and seasons to see when shadow impact is most noticeable.

- **3D map context**: View the planned mass in relation to nearby streets, lots, buildings, and terrain.

- **Solar position data**: Use azimuth, elevation, and shadow direction to understand why the shadow falls where it does.

## Mistakes to avoid
- **Testing one date**: One sunny day is not enough. Check solstice periods and the months when people use the affected space.
- **Forgetting height**: Height changes shadow length quickly, especially when the sun is low.
- **Treating a preview as approval evidence**: A visual preview is useful for planning, but formal approvals need the correct professional process.

## Limits

SunCast is suitable for preliminary shadow review. It is not a certified planning, surveying, engineering, or permitting tool.

## Check It in SunCast

Planning a structure or extension? SunCast helps you preview shadow direction and seasonal impact before the formal design work starts.

- [Download SunCast](https://apps.apple.com/app/id6757196901)

- [Check sun direction](https://suncastapp.com/tools/sun-calculator)

## FAQ

### Can SunCast simulate a future building?

Yes. Construction Mode lets you place a virtual building block and adjust its size and rotation to preview likely shadows.

### What dates should I check for building shadows?

Check winter, summer, and the months when the affected space matters most. Winter often creates the longest and most sensitive shadows.

### Can I use this for a planning application?

Use SunCast for early review and communication. For a planning application, use the required professional studies, drawings, and local process.

## Related SunCast Pages
- [SunCast facts and methodology](https://suncastapp.com/facts)
- [Sun position accuracy guide](https://suncastapp.com/guides/how-accurate-are-sun-position-apps)
- [Sun calculator](https://suncastapp.com/tools/sun-calculator)
- [All SunCast guides](https://suncastapp.com/guides)