The Box vent might be the most common type of roof exhaust vent made. If you try to picture a box vent in your head you probably have imagined something fairly accurate. They are boxes installed into the roof in strategic locations to move heat and moisture out of your attic by providing an outlet for air to exit the space.
Why are they so popular? Box vents are very economical and do a pretty good job of ventilating air when your home has good intake ventilation. That most common application is on homes with an “open” attic. They are not usually put near the ridge of your roof and their installation is fairly simple and economical. The downside is that they have a limit to their airflow and usually a fair amount of them have to be installed at regular intervals. Each installation, even when done properly, creates a greater potential for a leak than simply having shingles in that location.