To estimate how many hours of sunlight a garden will receive, choose a representative point, model the buildings and important trees around it, and calculate direct sun across several seasonal dates. The most useful result shows the time of day as well as the total duration.
Planning an extension while keeping a sunny garden
In this fictional example, Maya owns a terraced house with a compact garden. The kitchen receives weak morning light, the family uses a table near the rear boundary after work, and a sunny strip along one side supports herbs and vegetables. She is considering a deeper single-storey extension, but the first concept places a tall parapet close to the garden. A second concept is shallower and uses a lower edge.
Maya needs to know how the two proposed options change sunlight at three real places: the evening table, the vegetable bed and the neighbour-facing edge. She also wants a result she can discuss with her architect with a clear understanding of what the early estimate covers.
This guide is designed for Maya and readers in the same position: homeowners, gardeners, landscape designers and small residential teams making an early choice before every dimension is verified. The method gives them a structured comparison and tells them when to stop and obtain better information.
What “hours of sunlight” means in a shadow study
Yamaken Shadow Study samples the selected point every 10 minutes between approximate sunrise and sunset. At each sample, it tests whether a loaded building or planned object blocks the sun. The total “Direct sun” is the sampled daylight time without a modelled obstruction.
This is direct geometric sunlight at one ground point. It does not predict cloud cover, reflected light, soil moisture, plant performance or the brightness of a room. Those are separate questions. The calculation is most useful for comparing physical options at the same location, date and point.
Choose garden points that match real use
| Garden question | Suggested analysis point | What to read |
|---|---|---|
| Breakfast terrace | Ground point at the planned table position or centre of the occupied area | First sun and morning blocked intervals |
| Vegetable bed | Centre and, for a large bed, one point near each end | Direct-sun duration and longest blocked period |
| Children’s play area | Main play surface | The times relevant to actual use, including summer shade |
| Ground-floor window | A point close to the façade; interpret with care because the tool measures ground points | Differences between options, then verify with a façade-specific study |
| Proposed extension | Key points in the remaining garden and beside affected windows | Sunlight lost against Existing and the object causing it |
A worked garden example: compare use, not one score
Maya creates Existing with the current house and important neighbouring context. Proposal A adds the full-depth extension. Proposal B adds the shallower alternative. She saves three analysis points with clear names in her notes, then runs each point on the same dates.
Point 1: the evening table
On a summer test date, the shared timeline shows that Proposal A loses part of the direct-sun period between 5:00 and 6:00 pm, when the family uses the table. The daily total alone would hide why that loss matters. Proposal B retains most of that interval. The timing makes Proposal B more useful even if both options have similar daily totals.
Point 2: the vegetable bed
Both proposals retain a long midday period in summer. On the intermediate date, Proposal A creates an additional blocked interval while Proposal B remains close to Existing. Maya does not use the result as a guarantee that a crop will thrive. She uses it to decide that the bed should remain in place while planting advice considers species, soil, weather and maintenance separately.
Point 3: the neighbour-facing edge
The main cause note identifies the new extension object as the largest source of added shade. Maya asks the architect to test a lower parapet and a small setback. The revised Proposal B reduces the lost period. That gives the architect a specific design move to develop and gives Maya a clear explanation for the added construction complexity.
The example is fictional and the durations will depend on the real site. Its lesson is transferable: a garden has several uses, and each use deserves a point and time period. Do not average a breakfast corner, planting bed and evening terrace into one vague “garden sunlight” number.
A practical seasonal test
- Set the exact place. Confirm the map marker, coordinates and local time zone.
- Load nearby buildings. Check whether important neighbours appear and whether their heights are mapped, floor-derived or estimated.
- Model the current garden context. Check whether the house is already in the loaded OSM context before adding it manually. Imported OSM buildings remain shared across scenarios and cannot be removed by deleting a planned object. Add a simple tree object for a large, relevant canopy.
- Create the proposal. Copy Existing into Proposal A, then add the extension, garden studio, wall or other planned mass. Use Proposal B for a reduced height, larger setback or rotated alternative.
- Pick the garden point. Use the same point in all three scenarios.
- Test several dates. Repeat the calculation for a winter condition, an intermediate spring or autumn condition, and a summer condition. Add a project-specific date when the garden has a particular event or use.
- Save each result. Copy the reproducible link or create a report so the date and assumptions remain attached to the conclusion.
How to read a proposal that changes the timing
A proposal can lose one hour in the morning and gain another hour later. A net total alone would describe that as no change. The shared timeline shows whether the sun moved into a useful or less useful part of the day, while the gained and lost values preserve both effects.
If the result names a proposed building as the main added-shade source, test a specific response: reduce the height, pull the upper storey back, move the footprint, split the mass or compare a different orientation. Recalculate after each meaningful change. That turns the shadow study into a design loop rather than a final illustration.
Trees, fences and terrain
OpenStreetMap building context does not supply a complete vegetation model. Add important trees as planned objects when a simple canopy approximation helps the comparison. Remember that real foliage changes by species, season, density and maintenance.
Small fences, pergolas, retaining walls and garden structures may also be absent from map data. Add a simple object when one materially affects the chosen point. Terrain can change the horizon, but the daily point comparison currently focuses on loaded buildings and planned objects; inspect the separate terrain layer and record that it is not included in the daily point totals.
How to make the result useful in a design conversation
Before meeting a designer, Maya saves one link for each important date and creates a short report for the preferred point. Her note says what is known, what is estimated and what she wants to decide. She avoids asking, “Will the garden be dark?” and instead asks, “Can we keep the 5:00–6:00 pm direct-sun period at the table while retaining most of the proposed floor area?”
A useful homeowner record contains the point name, intended activity, date, Existing result, proposal changes, main modelled cause and uncertain context. Add photographs or a sketch outside the tool when they help another person locate the point. If a neighbour’s building height is estimated, mark it for verification. Tree objects are opaque approximations in the point calculation; they do not simulate light passing through leaves or winter branches. Record that assumption when trees matter.
This record helps the professional team respond to the actual concern. It can also prevent a later presentation from relying on a different point or convenient date without explaining the change.
Design moves worth testing
- Reduce depth: pull the extension away from the most valued sunny area.
- Lower the garden-facing volume: compare a lower object height. Detailed roof profiles need a more detailed calculation.
- Set back an upper floor: preserve a useful period while retaining space elsewhere.
- Move a detached studio: test position and rotation instead of changing only height.
- Split the footprint: create a gap that allows sun during a chosen part of the day.
- Move the activity: when the building cannot change, compare a better position for seating or planting.
Each move should become a clear proposal scenario. Recalculate with the same point and date, then keep the option that is both realistic and better aligned with the garden brief.
When the estimate needs a more detailed study
- A neighbour-impact or planning submission must follow a prescribed local method.
- A critical building outline, height, roof form or ground level is missing or uncertain.
- The conclusion depends on light through a window or inside a room.
- A large tree canopy, seasonal foliage or complex terrain drives the result.
- The point lies very close to a shadow edge, where small geometry changes can switch a sample.
- The decision carries material construction, property or legal consequences.
At that stage, obtain verified survey information and use the assessment method required for the project. Keep the early study as a record of the design alternatives you tested, rather than presenting it as the final compliance evidence.
Follow where the sunny area moves
A fixed point answers a fixed question, but a household can sometimes move the activity. After testing the current table, Maya places a second point a few metres away. The alternative position may retain evening sun without changing the building. This does not erase an impact at the original point; it reveals another practical response.
Use this approach carefully. Keep the original point in the record, name the alternative, and explain why moving the use is acceptable. It may work for movable seating or containers. It is less helpful for a neighbour’s window, an established tree, an accessible route or a space fixed by the wider design.
A point sequence can also guide landscape layout. Test the likely table position, a flexible lawn area and two ends of a planting bed. The result shows where direct sun occurs geometrically; a landscape or horticultural decision still needs weather, soil, water and species knowledge.
Check a garden point for free
Place an analysis point in the garden, compare Existing with two proposals, and see direct sun, blocked intervals and the main modelled cause on one timeline.
Open Yamaken Shadow Study →Frequently asked questions
How many dates should I test?
Start with a winter date, a spring or autumn date, and a summer date appropriate to the site’s hemisphere. Add dates tied to the actual use or a required local assessment method.
Where should I put the point in a large garden?
Use several labelled points: for example, the main terrace, the centre of a planting bed and the area closest to the proposal. One point should represent one clear question.
Does direct sunlight mean the garden will be warm?
No. Air temperature, wind, surfaces, soil, moisture and weather all affect thermal conditions. The result estimates geometric access to direct sun.
