Before signing a compromise, most buyers check the surface area, the price per square meter, and the condition of the roof. The actual sunlight exposure of the property often takes a back seat. This is a costly mistake: a poorly oriented house or one obscured by a neighboring building can turn a bright living room into a dark room as early as November. Google Earth and solar simulation tools allow you to check this point even before the first visit.
Shadows Cast by Neighboring Buildings: The Invisible Criterion of Real Estate Purchase
Have you ever noticed that a south-facing house can still lack light? The problem rarely comes from the orientation itself. It comes from the obstacles around: a four-story building to the south, a row of tall trees to the east, or a terrain that blocks the low winter sun.
This is exactly what hourly shadow simulation 3D tools allow you to evaluate. Google Earth, with its three-dimensional modeling of buildings, makes the projection of shadows on a plot visible at different times of the day. Platforms like Shadowmap go even further: they cross the geometry of buildings with terrain data and sometimes vegetation to produce an accurate shadow map for the entire year.
In practice, two adjoining houses on the same street can receive very different sunlight durations depending on the height of the buildings opposite. Checking this parameter on a screen takes a few minutes. Noticing it after moving in takes years.
The process of sunlight simulation with Google Earth remains the most accessible starting point for an individual, as you just need to switch to 3D satellite view and observe the sun’s path over the targeted land.
Solar Simulation on Google Earth: What the Tool Really Shows
Google Earth displays buildings in volume in most urban areas. To utilize this view, activate the “3D Buildings” layer and position yourself above the plot of interest.
Identifying Orientation Without a Compass
The north is always at the top of the screen by default. By observing the main facade in relation to this axis, you can deduce the exposure in a few seconds. But orientation alone is not enough. Rotate the view to examine the volumes around the house.
Reading Shadows in 3D
Google Earth allows you to modify the time and date of the sun display via the time slider (accessible under “Sun” in the View menu). Slide this slider to a winter day, for example in December, to observe the shadows at the time when they are the longest. This is the critical period: if the plot receives direct sunlight in December at noon, it will receive it all year round.
Repeat the operation in summer to check that the terrace or garden does not end up in full sun without any protection between 12 PM and 4 PM, which poses an inverse comfort problem.
Google Solar API and Complementary Tools to Go Further
Google has developed a Solar API that analyzes the solar potential of a roof based on aerial imaging data and 3D models. This tool is aimed more at professionals and developers, but several public sites use it to provide estimates of photovoltaic production.
For a buyer, the interest is twofold. First, to assess the profitability of solar panels before purchasing: a north-facing roof with a permanent shadow mask does not justify the same investment as a fully exposed south-facing roof. Second, to objectively compare two properties located on different streets.
Other free tools complement the analysis:
- Shadowmap offers a 3D shadow mapping accessible from a browser, with precise hourly settings and consideration of surrounding buildings.
- Regional solar cadastres (available in several French metropolitan areas) cross roof data with local irradiation to estimate photovoltaic potential plot by plot.
- SketchUp allows you to project realistic shadows onto an imported 3D model, helping to simulate the impact of a future neighboring construction on your sunlight exposure.
Four Concrete Checks Before Signing a Compromise
The sunlight analysis does not replace an on-site visit, but it effectively filters properties before traveling. Here are the points to systematically check.
- Winter shadow at noon: if the south facade is in shadow at 12 PM in December on Google Earth, the living room will lack natural light for several months.
- Deciduous or evergreen vegetation: a deciduous tree lets in winter sun, while a conifer blocks it all year round. Google Earth does not always distinguish this detail, so a field check remains necessary.
- Nearby construction projects: consult the local urban planning plan to see if a neighboring plot can accommodate a multi-story building that would radically change the sunlight exposure.
- Consistency between orientation and interior layout: a south-facing house with the living room on the north side loses the advantage of its orientation. Cross-check the property’s plan with the satellite view to ensure that the living spaces actually benefit from the light.
These checks take about twenty minutes per property. On a purchase project worth several hundred thousand euros, this preparation time avoids lasting regrets. A bright property in summer but dark from October to March loses comfort and resale value. Sunlight simulation transforms a vague intuition into observable data, well before the signing at the notary’s office.