Roof intake, exhaust and the paths between them

A vented roof needs a connected route.

For a conventional vented attic, a typical arrangement uses lower openings near the eaves and higher openings to the exterior. The useful assessment looks at the openings and the route connecting them. Baffles can maintain the space between insulation and the roof near the eaves; a blocked path prevents an opening from serving its intended purpose.¹

Do not choose a remedy by counting the vents visible from the street. Roof sections, obstructions, product free area and the intended airflow arrangement all need to be understood.

Follow one path on a sketch.

Ask the contractor to mark where outdoor air is intended to enter, how it reaches the roof space, and where it is intended to leave. Then repeat that exercise for each separate roof section. Label proposed changes and the parts staying in place.

For an eave intake, the drawing should make clear whether the opening connects to the attic past the insulation. At a ridge or other high opening, ask how the selected product will be installed and which roof space it serves. Use product instructions and the design appropriate to the assembly.

Check the weak links in the proposal.

• Hidden restrictions: What evidence shows that the intended path is clear?
• Separate roof spaces: Are additions and dormers being assessed independently?
• Existing vent types: How do the old and new openings work together?
• Weather details: How will the products be integrated into the roof and protected against the conditions expected at the property?
• Maintenance: Which screens, openings or other components need later inspection?

Use product free area consistently.

Ask for the manufacturer's stated net free ventilation area, not the size of the grille or the opening in the roof. Keep intake and exhaust totals separate. Record whether a value is per vent, per unit length or for the whole installed product; multiplying the wrong basis produces an impressive but meaningless total.

The net free area guide walks through a simple arithmetic example. The worksheet keeps the source values with the calculation for later review.

Agree what completion will show.

Request photographs of details that will be concealed, a product list and confirmation of any deviations from the approved scope. If an intended path could not be created, record it as an unresolved item with a next step. A completion photo of a new roof vent alone does not show the eave path.

Before the work begins, agree who will assess the result if moisture, ice or another original concern recurs. Ask what further information would be collected rather than expecting a universal guarantee from a vent replacement.