How the Sun Score works

Why a plan needs a score per block

Every plan on Dudils has already been through an architect review and is only published if its living areas can face north. That is a fact about the plan. It is not yet a fact about your land. The same plan can be a bright home on one block and a dim one two streets away, because the block faces a different way and the driveway has to come off a different side.

So the score is measured at the orientation that actually matched. Dudils tests all four quarter turns of a plan against your block dimensions, your driveway side and your filters, and keeps the turn that puts the most living area toward north. The Sun Score is read at that position, not at an average of the four, and not at whichever way the builder happened to draw the floor plan.

The four parts and what they are worth

Where each number comes from

North living run, 45 points

The biggest share, because it is the thing that decides whether the house gets winter sun at all. We take the width of the plan wall that ends up facing north and compare it with the run of your block along that same axis, which we read off the cadastre boundary. A plan that fills the north run of your block scores the full 45. A plan that presents a narrow end to the north scores a fraction of it. There is a ceiling on the block run in that comparison, so a very wide block does not make every plan look bad.

Windows on the north facade, 20 points

A north wall with no glass in it is a wall. Where a plan has had its windows marked up by hand on the floor plan, we take those markers, apply the same rotation and any mirroring that the matched placement used, and work out what share of the window run lands on the north side. All of it on the north gives the full 20.

Garage as buffer, 20 points

A garage is an unheated room you can put between the weather and the rooms you live in. On the south it blocks the cold side. On the west it takes the worst of the summer afternoon. On the east it is doing little. On the north it is sitting on the one wall you wanted for free winter heat, so it scores nothing. The score uses the garage side after the matched rotation, so it reflects where your driveway can actually come off the street.

Ground falls toward the sun, 15 points

The smallest share, because it is the thing you can most readily design around. We read the fall of your block off Geoscience Australia’s 5 metre LiDAR elevation model, the same reading our slope calculator shows you. Ground falling to the north lets low winter sun reach in under the eaves. Ground falling to the south turns the site away from it. A near level block sits in the middle, and a fall that runs only east to west sits in the middle too, because it barely changes the winter answer.

What happens when we cannot measure something

The honest version, because a score that hides its gaps is worse than no score. There are two kinds of gap and we treat them differently on purpose.

A gap about your block, such as no elevation coverage for the slope, is missing for every plan on that block equally. So we drop that part and scale the remaining parts back up to 100, and we say on screen that it was not counted. Because the gap is the same for every plan you are looking at, dropping it can move the numbers you read but can never change which plan comes first. That is also why a slope reading arriving a moment after your results does not reshuffle the grid under your hand.

A gap about one plan is the window markers. Those are placed by hand, plan by plan, and coverage is still growing across the catalogue. A plan whose windows have not been marked yet gets a neutral middle mark for that part, labelled “Windows not yet assessed” everywhere the score is shown. We do not drop and rescale there, because that would quietly reward a plan for not having been assessed. Neutral is defensible, because every published plan already carries the architect check that its living areas can face north. The most this can move a score either way is 8 points out of 100.

A plan with no garage, a granny flat for instance, has no garage part to score. That part drops out and the rest scale up, the same way a missing block reading does.

Sometimes there is no score at all. If no quarter turn of a plan puts a wall toward north within your filters, we would be inventing a number, so we show none. The plan keeps its place in the fit order and you can still open it.

What the Sun Score is not

• Not a NatHERS assessment and not a star rating. NatHERS is a regulated national scheme, and only an accredited assessor running an approved thermal engine can produce a rating under it. If you need one for a development application, a construction certificate or your own peace of mind, engage an accredited NatHERS assessor.
• No thermal simulation. We do not model glazing performance, insulation, thermal mass, air tightness, ceiling heights, eaves depth or the construction the builder will actually use. Two houses with the same Sun Score can be built very differently.
• No neighbour overshadowing. We do not model the two storey house next door, the fence, the trees or the hill behind you. The score reads your block, not what stands around it.
• No climate zone modelling. The weights above are the same everywhere. Winter sun arrives from the north across Australia, but how much it is worth to you differs between Hobart and Darwin, and the score does not attempt that.
• Not a promise about your finished home. It scores the plan as drawn against the block as mapped. Move a wall, change the driveway or turn the house and the answer changes with it.

Version

Sun Score version 2026.08. The method and the weights on this page are versioned together with the code that calculates them, so if we change how a part is scored we change the version and this page in the same breath. A score you screenshot today was produced by the method written above.

Every plan we publish has already passed the architect review set out in our review methodology. The Sun Score is the next question after that one: of the plans that can face north, which ones make the most of the block you are standing on.