A cupola can be attached to a roof at any time, though they have traditionally been installed when the house was built. A cupola looks like a design element, but is actually a vent build alongside the ridge of the roof. Natural convection allows air to flow up to it. There are louvers on four sides to provide ventilation.

Cupolas can provide great ventilation. They are easy to install, especially the pre-fabricated models, and they are low maintenance. Some models also include windows. The size can be calulated with a simple benchmark measurement: for one foot of ridgeline on the roof, figure one inch of base width for the cupola.