Anzon WongAW Design
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Hong Kong decided twenty years ago that wind at street level is a planning matter

By Anzon Wong2 min read3 plates

Plate 01 / 03

Hong Kong decided twenty years ago that wind at street level is a planning matter. Since 2006, Technical Circular No. 1/06 has asked for an Air Ventilation Assessment (AVA) on major government projects. The formal study comes once there is a scheme to test. The choices that shape the wind usually come earlier: where the tower sits on the podium, which way the slab faces, whether a gap stays open to the prevailing wind.

So I built a small tool for that earlier moment. HK Wind Sketch runs in a web browser. Search any place in Hong Kong and the page pulls the Lands Department's building heights and 5 m terrain model for a 600 m square, then runs a small lattice Boltzmann wind simulation in 3D on your own graphics card. Pick a wind direction from the Planning Department's site wind data, draw a block corner by corner, and watch the streamlines climb the hillside and bend around it. The images show one block in Mid-Levels under an east wind and a south wind.

The images show one block in Mid-Levels under an east wind and a south wind.

Plate 02 / 03

What building it taught me:

  • Terrain matters as much as buildings. On the Mid-Levels slopes the hill steers the flow before any tower does. A flat 2D slice could not show that, so version 3 added the terrain.
  • One direction is never the answer. The same block reads very differently under an east and a south wind. The habit worth building is testing several directions, not making one good picture.
  • Honest limits are part of the design. Grid cells are 4 to 6 m, so narrow lanes close up. There is no wind velocity ratio, no pass or fail, nothing on wind loads, and no validation against a wind tunnel. It is a sketch for early design and teaching, never an AVA. TC 1/06 itself says CFD "may be used with caution" even in formal studies.

I built it in my own time with an AI coding agent. It is free and open source under the MIT licence. Data: Lands Department and Planning Department, HKSAR Government (DATA.GOV.HK).

If you work on air ventilation in Hong Kong: at which design stage would a sketch like this help most?

The interactive tool is in the first comment.

Plate 03 / 03
See the original post on LinkedIn →

The same topic on Facebook: Add one 80 m block on Robinson Road in Mid-Levels

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