Channeled vents versus cross ventilation

Insulation · Flat and Cathedral Roofs · printed page 250 (PDF page 251)

Book index entries

Channeled Vents versus Cross Ventilation Channeled Vents versus Cross Ventilation Roofs Cross Ventilation versus Channeled Vents for Cathedral Roof Venting Roof – Channeled vents versus cross ventilation

Text in the illustration

for cathedral ceilings and flat roofs the recommended vent area is 1 square foot for every 150 square feet of roof area
3" air space
roof sheathing
shingles
roof rafter
soffit vent
air flow
siding
wall stud
insulation
drywall
cross section
channeled vents
roof membrane
1" below top of joist
2"x 2" purlins (perpendicular to joists)
roof joist
cross ventilation
open web trusses also permit cross ventilation

Generated explanation

Two roof-to-wall cross sections compare channeled ventilation with cross ventilation for cathedral ceilings and flat roofs. The left drawing shows air entering a soffit vent and traveling up a sloped shingle roof through a labeled 3-inch air space between the insulation and roof sheathing. The right drawing shows a membrane roof with sheathing supported on 2-by-2 purlins perpendicular to the roof joists, with insulation held 1 inch below the joist tops to provide interconnected ventilation space. Both sections show insulated stud walls, siding, and interior drywall, with bold arrows indicating airflow from the soffits into the roof spaces. Notes state a recommended vent area of 1 square foot per 150 square feet of roof area and indicate that open web trusses also permit cross ventilation.

Components

roof sheathing shingles roof membrane roof rafters roof joists purlins soffit vents ventilation air spaces roof insulation wall insulation wall studs drywall siding

Materials

wood framing batt insulation drywall roofing shingles roofing membrane