Stack Effect & Building Pressure Visualized
For healthcare & critical environments
City high-rise buildings
Winter · Summer · Neutral Stack

Experience the stack effect behind your building’s airflow.

Visualize how temperature differences and building height create pressure zones that drive infiltration, exfiltration, and neutral pressure planes in real facilities.

Start Stack Effect SimulationView Formula
Winter

Warm indoor air rises, drawing cold air in at the base and pushing out at the roof.

Summer

Cool indoor air sinks and spills out low, while hot outdoor air is drawn in high.

Neutral

Small ΔT and moderate heights bring the neutral pressure plane closer to mid-height.

Stack Effect SnapshotLive
Regime
Based on outdoor vs. 21°C indoor.
Winter (Stack)
ΔT = 31°C
ΔP across height
Simplified buoyancy-based estimate.
0.0 Pa
H = 100 m
Neutral Pressure Plane (NPP)~50% height

Educational visualization only. For actual healthcare facilities, AWPB applies standards-based testing and field measurements.

Winter (Stack Effect)

Warm indoor air rises and escapes at the top, pulling cold air in at the base. Negative pressure at low levels, positive at upper levels.

Summer (Reverse Stack)

Cool, dense indoor air sinks and spills out low; hot outdoor air is drawn in higher up. Pressure pattern inverts compared to winter.

The Driving Force

ΔT (temperature difference) and building height determine how strong stack effect is. Taller shafts + large ΔT = higher ΔP.

Building Pressure Simulator

Adjust outdoor temperature and building height to see how stack effect shifts pressure and the neutral pressure plane.

Simulation Controls

-30°C40°C
10 m400 m

Calculated Physics (Simplified)

Pressure difference ΔP0.0 Pa
RegimeWinter (Stack)
Estimated NPP height~50% of height
ROOF / PENTHOUSE
NPP
LOBBY / GRADE

INDOOR

21°C (reference)

How Stack Effect Happens

A simplified view of how buoyancy, temperature, and height interact in real buildings.

The stack effect is driven by buoyancy. Warm air is less dense than cold air. In winter, the warm air inside a building rises and escapes high openings, creating positive pressure at the top and negative pressure at the bottom.

In summer, if the indoor air is cooler than outdoors, the pattern can reverse. Dense, conditioned air sinks, spills out at low levels, and draws warmer outdoor air in higher – this is often called reverse stack.

Between these zones is the neutral pressure plane (NPP) where indoor and outdoor pressures are equal. Above the NPP, air tends to exfiltrate; below it, air tends to infiltrate.

Simplified equation

ΔP ≈ C · h · (1 / Tout - 1 / Tin)
  • ΔP = pressure difference across height (Pa)
  • C = constant combining air density, gravity, etc.
  • h = height between two openings (m)
  • Tout, Tin = absolute temperatures (K)

This simulator uses a greatly simplified relationship for education only. AWPB uses field measurements, codes, and commissioning procedures for real projects.

Why Stack Effect Matters in Healthcare

Small pressure errors can compromise infection control and pharmacy safety.

Operating Rooms

Stack effect can either support or fight against OR positive pressure.

AWPB verifies supply, exhaust, and door pressure relationships to keep ORs reliably positive to corridors in both winter and summer conditions.

AIIR & Isolation Rooms

Negative rooms must stay negative even when stack effect changes sign.

We validate direction of airflow, exhaust dominance, and door undercut performance across seasons and building operating modes.

Pharmacies & Clean Rooms

Door cascades and pressurization hierarchies can be distorted by stack forces.

Our TAB work considers both local airflow and building-scale effects like shafts and risers.

Is your building affected by stack effect? AWPB can support design reviews, commissioning, and investigative TAB to diagnose difficult pressure problems.

Talk to a healthcare TAB specialist