When cold air enters a building through the floor above a crawl space, where is the air exfiltration likely to occur?

The situation describes cold air entering a building through the floor above a crawl space, which creates specific airflow dynamics influenced by the building's pressure zones. In this context, the neutral pressure plane plays a crucial role in understanding air movement.

The neutral pressure plane is the level within a building where the air pressure is equal to that of the outside air. Above this plane, the building typically experiences negative pressure, causing air to be drawn into the building from outside. Conversely, below this plane, the pressure is usually positive, which means that air is pushed out of the building. When cold air enters the building from the floor above a crawl space, it indicates a disturbance in the pressure balance, leading to potential exfiltration above the neutral pressure plane.

This means that as the cold air enters, the warmer air inside may be forced out through gaps and leaks in the building envelope, predominantly located above the neutral pressure plane. Air exfiltration at this level often occurs through ventilation points, cracks, or openings in walls and ceilings. Understanding this flow of air is key for building analysts aiming to improve energy efficiency and maintain indoor comfort by addressing undesirable drafts and thermal losses.