What are ideal outdoor conditions for natural draft?

Natural draft relies on the difference in temperature and density between the hot gases produced by combustion and the cooler outside air to create movement. In cold and windy conditions, the cooler outside air is more dense, which enhances the stack effect. This means that as the hot gases rise, the colder air being pulled in from below aids in creating a stronger draft. Wind can further assist in pushing smoke or gases up through the chimney since it increases the pressure differential; thus, it encourages the natural ascending flow of air.

In contrast, warmer and humid conditions can lead to a less effective draft, as the temperature difference is reduced. Windy conditions are ideal, facilitating a more robust natural draft compared to other scenarios where humidity or calmness can impede air movement. Therefore, cold and windy conditions are the most effective for ensuring a strong natural draft in a boiler or chimney system.