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Open windows and pass the daylight check

Put windows into habitable rooms and pass koyu light's one-seventh test — effective window area ≥ floor area ÷ 7.

File paths in the output below are absolute when you actually run these commands. They are shortened to bare filenames here for readability.

Before you start​

  • koyu check passes with zero errors.
  • You have decided which rooms are to be judged. koyu does not guess.

1. Declare that a room is in scope​

light looks only at spaces carrying daylight:1. It never looks at the type. Whether a room is judged is something the author declares, not something inferred from what the room is called. The default is out of scope, so with no daylight anywhere nothing is judged.

space /L1/a bedroom X1..X2 Y1..Y2 name:Bedroom daylight:1  # in scope
space /L1/b wet     X2..X3 Y1..Y2 name:Washroom            # default: out of scope
space /L1/c wet     X3..X4 Y1..Y2 name:Bathroom daylight:1 # type stays wet; judged anyway

daylight:0 means the same as the default, but writing it tells the reader that the exclusion was deliberate. The only values are 0 and 1.

✖ daylight-yes.muro:line 10: daylight is either 1 (in scope for the daylight check) or 0 (out of scope): /L1/a carries daylight:yes
✖ daylight-yes.muro:line 11: daylight is either 1 (in scope for the daylight check) or 0 (out of scope): /L1/b carries daylight:yes

Where you put daylight:1 also decides the grain of the denominator. Put it on an undivided unit and the whole dwelling is judged as one room; put it on the living room and bedrooms and each is judged separately. Both are correct — it is a choice about the resolution of the scheme.

With nothing in scope, light exits 0 — indistinguishable from "every room passes". When a room you expected does not appear, suspect a missing daylight:1 first.

$ npx tsx src/cli.ts light daylight-noscope.muro
Nothing is in daylight scope (write daylight:1 on the rooms to be judged)

2. Write window on a boundary that faces out​

A window counts only when the other side of that boundary is the exterior (exterior) or a semi-outdoor space. A window between two rooms contributes nothing (it is treated as zero).

boundary /L1/a /out t:150 spec:EW
  window w:2600 h:2200 edge:S name:Sliding-window

The attributes a window accepts are in window.

3. Write both w: and h:​

Width w: is required by the grammar; without it reading stops.

✖ daylight-now.muro:line 17: window requires a width w:(mm) (the asset may supply it)

Height h: is optional to the grammar, but light counts only windows that have one. A window without h: is not an error; it is treated as zero area, and light appends a note.

✖ /L1/a	Room-A	window 0.00 m2 / floor 16.20 m2 = no window (needs 1/7 ≈ 2.31 m2) ⚠ windows without h: are not counted

If the opening references a joinery asset, the h: may live on the asset (asset).

4. Pick the edge with edge: when the perimeter breaks into pieces​

A boundary with a space that has no region — /out and its like — is whatever is left of the room's perimeter after the parts touching other spaces are removed, and it usually falls on several sides. Say which with edge:N/E/S/W. N is +Y, S is −Y, E is +X, W is −X, read from the rectangle of the space written first on the boundary line.

✖ daylight-noedge.muro:line 17: There is more than one boundary segment; pick an edge with edge:N/E/S/W (/L1/a | /out)

Check it​

Run light. Exit 0 if every room in scope passes, 1 if any falls short.

koyu 1.0
name Daylight practice
unit mm

grid X 0 3600 7200
grid Y 0 4500
level L1 0 h:2400 slab:150
level R 2700 slab:150

space /L1/a room X1..X2 Y1..Y2 name:Room-A daylight:1
space /L1/b room X2..X3 Y1..Y2 name:Room-B daylight:1
space /out exterior name:Outside

boundary /L1/a /L1/b t:120
  door w:780 h:2000
boundary /L1/a /out t:150 spec:EW
  window w:2600 h:2200 edge:S name:Sliding-window
boundary /L1/b /out t:150 spec:EW
  door w:900 h:2100 edge:S at:X2+900 name:Front-door
  window w:2600 h:1100 edge:E name:High-window
$ npx tsx src/cli.ts light daylight.muro
✔ /L1/a	Room-A	window 5.72 m2 / floor 16.20 m2 = 1/2.8 (needs 1/7 ≈ 2.31 m2)
✔ /L1/b	Room-B	window 2.86 m2 / floor 16.20 m2 = 1/5.7 (needs 1/7 ≈ 2.31 m2)
✔ Every room meets 1/7 — 2 rooms in scope (a rough judgement with no correction factor — this is validation, not what check guarantees)

Read a line left to right: verdict, path, name, effective window area (after the coefficient), floor area, their ratio, the area required. A room with no window at all reads no window.

The same two rooms with the windows removed:

✖ /L1/a	Room-A	window 0.00 m2 / floor 16.20 m2 = no window (needs 1/7 ≈ 2.31 m2)
✖ /L1/b	Room-B	window 0.00 m2 / floor 16.20 m2 = no window (needs 1/7 ≈ 2.31 m2)
✖ Short of 1/7: 2 of 2 rooms (this is a validation judgement)

koyu validate says the same thing as daylight.ratio (a violation). Use that one in CI.

✖ [daylight.ratio] daylight-none.muro:line 10: Insufficient daylight: /L1/a — effective window 0.00 m2 < required 2.31 m2 (1/7 of the 16.20 m2 floor)
✖ [daylight.ratio] daylight-none.muro:line 11: Insufficient daylight: /L1/b — effective window 0.00 m2 < required 2.31 m2 (1/7 of the 16.20 m2 floor)

Daylight borrowed through a semi-outdoor space​

A window that faces a balcony, a terrace or a garden is discounted. If a space overlaps that semi-outdoor space from above, the coefficient is 0.7; if the sky is open, it is 1.0. Whether there is a roof is itself derived, so adding a balcony on the storey above drops the coefficient below it.

A sliding window (2600×2200 = 5.72 m²) onto an open terrace counts in full.

koyu 1.0
name Daylight through a terrace
unit mm

grid X 0 4000
grid Y 0 4000
level L1 0 h:2400 slab:150
level R 2700 slab:150

space /L1/liv living  X1..X2 Y1..Y2      name:Living-room daylight:1
space /L1/bal balcony X1..X2 Y1-1500..Y1 name:Terrace
space /out exterior name:Outside

boundary /L1/liv /L1/bal t:100 spec:Sash
  window w:2600 h:2200
boundary /L1/bal /out edge:S t:120 spec:Balustrade air:1 h:1100
✔ /L1/liv	Living-room	window 5.72 m2 / floor 16.00 m2 = 1/2.8 (needs 1/7 ≈ 2.29 m2)

Put a balcony on the storey above, in the same position, and the terrace is under cover: 0.7 applies. Neither the window nor the floor has changed.

koyu 1.0
name Daylight through a terrace
unit mm

grid X 0 4000
grid Y 0 4000
level L1 0 h:2400 slab:500
level L2 2900 h:2400 slab:500
level R 5800 slab:500

space /L1/liv living  X1..X2 Y1..Y2      name:Living-room daylight:1
space /L1/bal balcony X1..X2 Y1-1500..Y1 name:Terrace
space /L2/bal balcony X1..X2 Y1-1500..Y1 name:Balcony-above
space /out exterior name:Outside

boundary /L1/liv /L1/bal t:100 spec:Sash
  window w:2600 h:2200
boundary /L1/bal /out edge:S t:120 spec:Balustrade air:1 h:1100
boundary /L2/bal /out edge:S t:120 spec:Balustrade air:1 h:1100
✔ /L1/liv	Living-room	window 4.00 m2 / floor 16.00 m2 = 1/4.0 (needs 1/7 ≈ 2.29 m2)

A space is semi-outdoor only when it has a region and has an open or air:1 boundary to the exterior. A balcony whose balustrade is missing its air:1 is not semi-outdoor, and a window borrowing through it counts as zero.

✖ /L1/liv	Living-room	window 0.00 m2 / floor 16.00 m2 = no window (needs 1/7 ≈ 2.29 m2)
✖ Short of 1/7: 1 of 1 room (this is a validation judgement)

When it falls short​

Every ✖ line prints the area required. Reach it by one of:

  • Enlarge the window, or add more of them. Effective window area is the sum over every boundary of that space.
  • If it borrows through a semi-outdoor space, move the window onto a boundary that faces the exterior directly. The coefficient becomes 1.0.
  • If the room need not be judged, drop daylight:1. Write daylight:0 to keep the intent visible.
  • Make the floor smaller. One-seventh is a ratio of areas, so a deep room can fail even with glazing across its whole face. Choose dimensions before you write has the rules of thumb.

light is a rough early warning with no correction factors. It is not a compliance judgement. What it does and does not claim is in the daylight rule.

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