Heights, Storeys & Shade

A roof drawn in plan has no heights. This is where they come from, and where the trees that shade it are measured.

How heights solve

Every junction on the roof takes its height from one rule:

height = eave height + distance to the nearest eave × tan(pitch)

So two numbers describe an ordinary house: where the eave is, and how steep the roof is. Set the storeys on the 3D step — 1, 2 or 3 — and the eave height follows.

A building with more than one eave

The rule above describes a house. It cannot, on its own, describe a mansion — a wing at two storeys against a body at three, another wing at one, a raking eave that climbs. Those are ordinary on any large building, and one eave height lifts the low wing to the tall eave and produces a roof that is not the building.

So heights are set per line. On the 2D design step, the Roof lines list holds every line on the roof:

1. Click a line in the list and it highlights on the map, so you can tell which row is the wing's eave rather than deducing it from an id.
2. Type its height above the site. The ▲ and ▼ buttons move it a quarter of a metre at a time, which is small enough to correct with and big enough to see.
3. Auto returns the line to the solved height.

A line you have set reads · set and its height is shown in the accent colour. Hips and rakes show a span — two ends at different heights — rather than pretending there is one number.

There is no limit of two. A roof may carry as many distinct heights as it has eaves; a large house routinely has three or four, and setting one never disturbs another.

Return every line to the solved height clears the lot at once when the overrides have got away from you.

The same list is where a line's type is corrected — eave, ridge, hip, valley, rake, gable wall. A type you pick is left alone by later automatic passes; one the tool guessed is re-derived as the roof gets more complete.

The 3D step

The 3D view is built from the roof planes, so it has nothing to show until they exist. It reports:

• Eave height and ridge height,
• the number of planes and the total roof area,
• and a line per plane: pitch · azimuth · area, with azimuth clockwise from true north.

What the 3D view shows

Roof planes with the satellite imagery draped over them, the walls under them, the modules, the trees, and — with the Equipment toggle — the service and the conduit between it.

Equipment is worth seeing here rather than only in plan, because both questions this view answers about a service are vertical: how far up the wall the panel is, and whether the run from the array crosses the ground or climbs the building. A panel entered at 1.4 m and one left at zero look identical on a map.

A trench is drawn below grade and a surface run above it, so the two read as the different pieces of work they are — one is a day with a machine and a crew, the other is a morning with a ladder.

Two overlays are worth turning on here and nowhere else:

Irradiance colours the roof by what each patch actually receives, blue through yellow, normalised across the whole roof rather than per plane — per plane makes every face look equally varied and hides the finding that matters, that one plane is worth half of another. In plan the map says where a roof is shaded; here, next to the tree casting it, it says by what. It is a per-cell walk of the whole roof, so it is computed only once you ask for it.

Sun path draws the sun's track across the day being scrubbed. It is the one thing a plan view cannot show at all: a roof either does or does not sit under where the sun actually goes, and in December that is a much lower and much shorter arc than most people picture. Below the horizon is not drawn — that would imply sun the site never sees.

The 3D view is a viewer, not an editor. The one thing you can change here is an obstruction's height, by dragging its top — because height is the input that most determines a shadow and the one nobody can judge from above.

"Not planar"

A face whose corners do not sit on one surface is reported rather than flattened. The panel names the face and says how far the worst corner is off the plane, in centimetres, and which corner it is.

A fitted plane through corners that are not coplanar is a number that looks like a roof and is not one. Raise or lower one of that face's lines to fix it — which is what the Roof lines list above is for.

Planes made by a generator are planes by construction, so there is nothing there that could fail; only a roof drawn as ridges and valleys gets checked properly.

Trees

A tree is the commonest cause of a production shortfall, and the one thing on a site survey that gets guessed at. Select a tree and four measurements are editable — every one of them changes the answer.

The clear stem is the field people skip and the one that separates a mature palm from a young conifer of the same height. They shade a roof completely differently, and the difference is entirely that number.

The panel confirms what you entered in plain terms — "6.5 m of foliage starting 2.5 m up" — and warns you when the trunk is as tall as the tree, because a tree with no canopy casts no shade at all.

Heights can also be dragged in the 3D view, which is the fast way to judge a result against the ridge it has to clear. Typing is the right way to enter a measurement off a site assessment.

Roof objects

Chimneys, vents and units are placed on the 2D step and must land on a roof plane — their height is measured from the surface they sit on, not from the ground. Their heights are set on the 3D step the same way trees' are.