PÉCLETBuilding Physics
PÉCLET / Disciplines / 03u — m/s · ACH — 1/h

Air

Air is the fastest way to move energy into or out of a building, and the hardest to draw.

QuantityPressure and flowTransportAdvectionInteractionDrag to change the wind direction. The flow field re-forms around the building.
Fig. 03 — Flow around and throughDrag anywhere on the field to turn the wind
Wind arriving from the W. The openings are open, so air passes both around and through the massing.
Wind fromW
Windward — flow separatesLeeward — flow stalls
Streams of particles flow across a building form from one side to the other. The flow separates at the windward face, accelerates around the corners, and forms a slow recirculating wake on the leeward side. Some particles pass through openings in the form and cross the interior. Particle brightness indicates local speed.

The position

Wind pressure, stack effect and mechanical supply compete at every opening. The result decides whether a space is ventilated or merely leaky — the two look identical on a plan and behave nothing alike.

Airtightness is not the opposite of ventilation. It is what makes ventilation controllable. We separate the two deliberately: seal the fabric, then choose where the air goes.

What we ask

  • 01Where does air enter, and where does it leave?
  • 02Does cross-ventilation exist here, or only in the render?
  • 03What happens to the flow path when the wind turns?
  • 04Is infiltration doing the job the ventilation strategy claims to do?

How we answer it

  • 01Natural ventilation strategy development
  • 02Airtightness line definition and continuity checking
  • 03Flow-path and pressure-regime assessment
  • 04Mixed-mode and seasonal operation logic