Can you trust it when a listing says a home is "south-facing"?
"South-facing" covers anything from 158 to 202 degrees and says nothing about where the windows sit or what casts a shadow — check it yourself with a compass bearing and a shadow angle.
Short answer: "South-facing" in a property listing isn't a measurement, it's a description — and it can be accurate and still worthless. The word says nothing about how many square metres of glass actually face south, how tall the neighbouring house is, or which room it applies to. Check it yourself: read the house's orientation as a bearing in degrees from a north arrow or a map, and measure the shadow angle to whatever stands to the south as arctan(height ÷ distance). If the shadow angle is bigger than the sun's height on the date in question — roughly 11° in December and 34° at the equinox, at a latitude like Copenhagen's — "south-facing" doesn't mean much.
What the word "south-facing" actually covers
There is no fixed definition of when a home counts as south-facing. In practice the word gets used for anything from a garden facade pointing due south, to a terrace facing south-west, to a flat where just one of five windows happens to face that way.
Even in the narrow sense — the 45-degree sector a compass calls south — the word covers bearings from 158° to 202°. That is a real difference: a house facing 158° gets sun through its garden facade earlier in the day and loses it earlier in the afternoon than a house at 202°.
The word isn't a lie, in other words. It just isn't a number. And sun calculations need a number.
Three things "south-facing" doesn't tell you
- How much glass actually faces south. A house with two narrow 0.6 m² windows facing south and a 4 m² picture window facing north is "south-facing" in the listing's sense of the word, and dark in practice. Count glass area by direction, not the number of windows.
- Which room it applies to. "South-facing garden" says nothing about the living room. "South-facing balcony" says nothing about the bedroom. Always ask: south-facing what?
- What's standing in the way. This is the big one. A south-facing living-room window with an 8-metre neighbouring house 15 metres away sits in shadow all winter, no matter how nicely it's oriented.
The sum that settles it
Two angles need to be compared. The first is the sun's height at solar noon, found from 90° − latitude + declination. At 55.7° north — Copenhagen's latitude, shared with southern Scotland and the Baltic states — that works out to roughly 11° at the winter solstice, 34° at the equinox and 57° at the summer solstice.
The second is the shadow angle to whatever stands south of the window: arctan(height ÷ distance).
Example: the neighbour's house is 8 metres to the ridge and stands 15 metres south of the living-room window. 8 ÷ 15 = 0.53, and arctan(0.53) = 28°. That's below the equinox figure of 34°, so the living room gets midday sun for the lighter half of the year — roughly from the start of March to the start of October. It's above the winter sun's 11°, so the room sits in shadow at midday for the rest of the year. The home is south-facing, and the listing is correct — but the winter light isn't there.
Turn the sum around if you want to know how far away a neighbouring house needs to be to leave the winter sun clear: height ÷ tan(11°) = height × 5.15. An 8-metre house needs 41 metres of clearance. On an ordinary suburban plot, you rarely find that much space to the south.
How to check the listing at a viewing
- Find north as a bearing in degrees before you go in: the north arrow on the floor plan, a map held with north up, or your phone's compass held against the outside wall. Write down "garden facade faces 187°", not "south-facing".
- Go room by room and note which way the windows face, and how much glass there is in each direction.
- Look south from every living space and estimate the height and distance of whatever you see. A storey is typically around 3 metres; a pitched roof adds 2-3 metres on top.
- Work out arctan(height ÷ distance) on the spot and hold the figure up against 11°, 34° and 57°.
- Take a photo facing south from every room. It's the cheapest record of the horizon you can bring home with you.
- Remember what season you're standing in. Deciduous trees are just bare branches in February and a dense screen in June. A winter viewing understates the shadow; a July viewing overstates the sun.
When the listing is correct and the home is still dark
There are three common cases where "south-facing" holds up, and the home is still darker than expected:
- A deep floor plan. Daylight roughly speaking only reaches 2 to 2.5 times the height from the floor to the top of the window into the room. If the top of the window sits 2.1 metres above the floor, the light reaches 4-5 metres in — the rest of an 8-metre-deep room is dark, regardless of which way it faces.
- Light from only one side. A room with windows in two walls feels noticeably brighter than a room with the same total glass area gathered into one wall, because the shadows cancel each other out. Corner rooms almost always win.
- Something overhead, right outside the glass. A covered terrace, a balcony above, or a deep overhang blocks sun all year round. An overhang sized to shade the 57° summer sun won't block the 11° winter sun — but a full roof over the terrace will.
Get the numbers before you make an offer
A property listing describes; a measurement settles the matter. The difference between the two isn't necessarily bad faith — it's that a word like "south-facing" simply can't carry the information a daylight study needs: a latitude, a bearing in degrees, a glass area per direction, and a shadow angle per window.
Those four things can all be gathered at a single viewing with a phone and a calculator. And if you also have the home's floor plan measured accurately and placed correctly on the map, the whole thing can be worked out from your own sofa. In HouseSense, the home is scanned with the iPhone's LiDAR and placed on the map, after which the sunlight falling on the 3D model is calculated for that exact address, that exact north direction, and whatever date you choose. So you can see the home's December while you're standing in it in August.