Introduced in 1986, the negative pressure roof system remains a niche design in the single-ply roofing industry. Also referred to as a ‘wind-vented’ roof, the science behind the system is simple. When an air seal is formed using a newly installed single-ply membrane, a low pressure condition is created on the underside of the roof. Any moisture in the existing wet roof insulation is pulled up through perimeter roof vents.