Why is the stack effect particularly noted in winter?

The stack effect is a phenomenon that occurs due to differences in temperature and density of air within a building, particularly noted in winter months. Warmer air inside a building is less dense than the colder air outside, leading to a situation where the warm air rises while creating a pressure difference.

In winter, buildings are typically heated, which increases the internal temperature and thereby the density difference between the air inside and the colder outside air. As the warm air rises, it escapes through openings at the upper parts of the building, which can create negative pressure at the lower levels, drawing cooler outside air in through openings. This effect can lead to drafts and can influence ventilation patterns within the structure.

Thus, the temperatures inside a building play a critical role in facilitating the stack effect, explaining why it's particularly noticeable during the colder months when the contrast between the inside and outside temperatures is most pronounced.