Daylight Analysis

Level 1 (Ground)

We want good daylight – a “daylight factor” (DF) if used with a uniform sky.

  • <2% is dim (dark blue)
  • 2% to 5% is good
  • More than 10% is pretty bright, but okay for outside areas

No windows

blackbox 2
L1: without windows, the house is dark! The deck is lit via open end. It is 5m deep and 2.5m high. Hence the “2H daylight rule” seems rule.

Standard Glazing (VLT 70) with current design

Standard clear has a visible light transmission of 92%. We use 70% to account for dirt (10%) and frames (10%).

L1 with standard glazing. Top right is the entry and dining – dark. This is despite a stairwell above . Maybe enlarge stairwell or add a window near entry to south. Kitchen is good with its clear splashback (mid right). Lounge (right) is good too (5% DF) but its dark under the south wall, which has high windows. Deck is good. B4 (top left) is okay but uni-directional. The bathroom is just okay.

L1 Improvements

Let’s fix these by:

  • B1: Enlarge window.
  • Bathroom: Paint light
  • Dining: Enlarge stairwell – can only easily enlarge by 100mm, increase VLT of window above and add window
image 9
With improvements. Bath ok. Dining better but not good. B1 ok.
image 10
Areas poorly lit (<2% DF) are grey. Hence just the dining (at about 1% DF) is not good.

So the final solutions are:

  • B1: Enlarge window.
  • Bathroom: Paint light
  • Dining: Enlarge stairwell, and increase VLT of window above and add window
    • The stairwell light above doesn’t seem to really improve things (strange), so
    • enlarge dining south window (1200×1200), paint dining light colours and maximise stairwell light with a minimal balustrade.
    • paint lounge light to reduce glare from high windows

The final L1 result is not too bad. The dining room is about 1.5%DF. Lounge is 4%.

image 11
Final Daylight. Clipped (grey) areas are dim.

And we can do some renders to get a ‘feel’ for the look of the improved daylight:

Daylight Factor: green is good. Red is bright. Dark blue is dim.
improved raw df
Dining room daylight factors: about 2.0DF so the improvements are just okay. Note the stairwell above is not providing a lot of illumination. This is unexpected from the plans, but makes sense in this view.

Level 2

Base Design

This will remain mostly unchanged so these is less design scope.

image 12
Base Design L2

I’ve lived in this house, so can comment on ‘real-world’ impressions.

  • Left: B1 and dressing is good, if dark at the back. Ok.
  • Top right: ensuite: white tiles will provide good lighting with 2 (450×1200) windows as shown. The others are blanked out.
  • Left middle: existing bathroom shows as poor, but is on the north and in reality is just ok.
  • Left bottom: B2, old kitchen shows as good and in reality is good. On north.
  • Right: both rooms are marginal, which is true in reality. Without resorting to western windows or major changes, some way of improving/enlarging existing windows (e.g. replace glass, paint white, remove sun hoods) would be good.


We can do a few things to improved:

  • Remove sunhoods to south
  • paint B2, B3 white and clean/open windows (e.g. remove bars)
  • B2 (on the right of image) can have translucent doors.
  • Existing bathroom (mid-left): replace lourves with window. Make clear at the top.

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