Roof venting arrangement and method

A venting arrangement for a roof, the roof having an insulation layer and a roof membrane on top of the insulation layer, the arrangement comprising:

• a plurality of perimeter venting stacks arranged spaced-apart around a perimeter of the roof, each said perimeter venting stack having a first open base end that is open to an area on the top of the insulation layer and below the roof membrane;
• a plurality of venting paths forming a grid on the roof, each said venting path comprising filter material that allows air to pass horizontally and vertically through the air filter material, the filter material arranged between the roof membrane and the insulation layer and extending lengthwise or widthwise across the roof and open at opposite ends to respective said first open base ends of the perimeter venting stacks located adjacent to opposite sides of the roof;
• wherein said each venting stack is supported on a base mesh fabric that allows air to pass vertically through the base mesh fabric that overlies a respective said venting path;
• wherein each said base mesh fabric has an outer perimeter greater than a perimeter of the respective first open base end that is supported on the base mesh fabric;
• wherein the filter material includes mutually interconnected voids which provide a sufficient air permeability such that ambient air flow on the roof past one of the plurality of venting stacks draws vapor through the respective venting path and creates a suction to urge the roof membrane down onto the insulation layer, and wherein the filter material does not transport said vapor by capillary action.

A method of venting a roof, the roof having an insulation layer and a roof membrane on top of the insulation layer, the method comprising:

• arranging a first venting stack having a first open base end open to an area on the top of the insulation layer and below the roof membrane;
• arranging an air venting path between the roof membrane and the insulation layer and in air flow communication at a first location to the first open base end of the first venting stack and extending to a second location away from the first venting stack;
• and
• arranging a second venting stack having a second open base end open to the area on the top of the insulation layer and below the roof membrane, the air venting path being in said air flow communication at the second location to the second open base end of the second venting stack;
• wherein the air venting path includes mutually interconnected voids which provide a sufficient air permeability such that ambient air flow on the roof past the first or second venting stacks draws vapor from the insulation layer vertically into the air venting path and horizontally through the air venting path and creates a suction to urge the roof membrane down onto the insulation layer, and wherein the air venting path does not transport said vapor by capillary action.