Ventilation system for roof

1. A roof vent comprising:

a roof cover layer vent member comprising a bottom plate and a top plate having downslope edges spaced apart to define an open downslope end with a gap between the plates, wherein the bottom plate comprises an opening to allow airflow between the gap and a space below the bottom plate, and wherein the bottom plate and the top plate are connected to each other upslope of the opening; and

a baffle connected to the bottom plate and positioned between the bottom plate and the top plate, wherein at least a portion of the baffle is positioned between the downslope edge and the opening, said portion of the baffle comprising a cross-section having a first portion extending upward from the bottom plate and a second portion extending from the first portion in a downslope direction away from the opening, to define a space between the bottom plate and the second portion.

2. The roof vent of claim 1 , further comprising a sheathing layer vent member having an aperture through which air from an attic may be ventilated, the sheathing layer vent member configured to be installed at an opening in a sheathing layer of a roof, with the aperture aligned with the opening.

3. The roof vent of claim 1 , wherein the baffle comprises first, second, and third sidewalls joined together, the first and second sidewalls positioned on opposite sides of the opening and oriented generally transverse to the downslope edge of the bottom plate, and the third sidewall positioned downslope of the opening and oriented generally parallel to the downslope edge of the bottom plate.

4. The roof vent of claim 3 , wherein the third sidewall comprises a U-shaped cross-section.

5. The roof vent of claim 3 , wherein the first and second sidewalls comprise an L-shaped cross-section.

6. A roof structure comprising:

a roof deck having a plurality of openings;

a plurality of primary vent members installed on the roof deck, each primary vent member having an aperture positioned in alignment with one of the openings in the roof deck so that the apertures permit airflow between regions above the roof deck and below the roof deck; and

a roof cover layer spaced above the roof deck to define an air layer therebetween, the roof cover layer comprising:

a plurality of non-vent roof cover elements, and

a plurality of secondary vent members each having at least one opening to permit airflow from the air layer to a space above the roof cover layer, wherein the aperture of each primary vent member and the at least one opening of each of the secondary vent members are offset with respect to each other;

wherein a total number of primary vent members in the roof structure is at least 1.5 times a total number of secondary vent members in the roof structure.

7. The roof structure of claim 6 , wherein each secondary vent member mimics an appearance of one or more of the non-vent roof cover elements.

8. The roof structure of claim 6 , wherein each secondary vent member comprises a bottom plate and a top plate spaced apart to define a gap therebetween, the at least one opening of the secondary vent member being formed within the bottom plate.

9. A roof structure comprising:

a layer of roof tiles that form a repeating pattern when assembled on a roof; and

at least one vent member that replaces and mimics an appearance of one or more of the roof tiles within said layer;

wherein the vent member comprises a cover member and a base member joined together and having downslope edges spaced apart, the base member having lateral end portions extending laterally beyond lateral edges of the cover member, each of the lateral end portions of the base member having a non-planar profile conforming to and engaging a similar profile of an horizontally adjacent roof tile.

10. The roof structure of claim 9 , wherein the vent member includes vertical walls extending from the base member to the lateral edges of the cover member to substantially prevent the ingress of water between the lateral edges of the cover member and the base member.