Negative Pressure Roofing System

Negative pressure is then applied to the dome starting at an initial pressure of 15 pounds per square foot psf.

Negative pressure roofing system. The kelly system is a passive system that simply transfers the negative pressure while v2t is an active system that generates greater negative pressures under the membrane than what is being exerted on the roof surface. Air is allowed into the room through a gap under the door typically about one half inch high. Continuous self drying of wet roofs with wind vented negative pressure system. The wv roof assembly creates a continual drying of the roof substrate.

A very small amount of positive pressure is ideal for a building but too much can cause damage. Water moisture damage within the roof turns to vapor in low pressures created by the wind vent system. Negative pressure is generated and maintained by a ventilation system that removes more air from the room than air is allowed into the room. Water in this gaseous state can then exit the roof via the one way vortex valves.

The negative pressure test utilizes a five foot by five foot dome that is placed over the roofing membrane surface. The second difference is the positioning and principles of operation of the two systems. Protan s vacuum system is based on the principle of anchoring the membrane by creating negative pressure in the layer between the membrane and the airtight substrate when exposed to wind loading. Because kelly system is designed to operate in the negative zone the vents must be positioned on the perimeter edge.

Loose laid air pressure equalization system. Apparently the negative pressure system is secured only at the perimeter the rest being loose laid i can t imagine how the mod bit versions of this idea work but the literature claims they do. Even if no damage is visible the effect to a roofing system with long term exposure to positive pressure is unknown. Constant daily pressure puts strain on hot air welds induction welds and adhesives.

The negative pressure roofing system is referred to as a wind vented roof and is proven in thousands of roof installations. Relieving vents installed at the perimeters result in negative pressure within the system during storms which purportedly suck the membrane tighter to the substrate.