Install Ridge Vent for Attic Ventilation

Goal

Install a continuous ridge vent that balances attic ventilation, prolongs roof life, prevents ice damming, + extends shingle warranty. Most older homes (pre-1990) lack adequate ridge ventilation; retrofit is a common upgrade during reroofing.

Why ridge vents matter

Ideal attic ventilation = balanced intake (soffit vents) + balanced exhaust (ridge vent). The "balanced" part is critical:

• Air flows from soffit IN, across attic, out through ridge
• Removes moisture (prevents mold, rot, condensation)
• Removes heat (lower attic temp = longer shingle life, lower cooling costs)
• Without balance: stagnant air, moisture problems

NRCA standard: 1 sq ft of net free ventilation per 150 sq ft of attic, split 50/50 intake/exhaust.

Prerequisites

• Ridge vent material (continuous strip type, not box vents)
• Soffit vents already present + adequate (or plan to add)
• Replacement ridge cap shingles
• Roofing nails (long enough to penetrate vent + deck + ridge cap)
• Saw with carbide blade (cuts through shingles + deck)
• Chalk line
• Pry bar
• Ladder + harness
• 2-3 hours for typical residential

Steps

Step 1: Verify soffit ventilation is adequate

1. Look in attic - can you see daylight at soffit edges? (Indicates intake clear)
2. If soffits are blocked with insulation, install soffit baffles
3. If soffits don't have vents, add them BEFORE ridge vent (otherwise the new ridge vent will pull air from the house through ceiling gaps, increasing energy bills)

Step 2: Mark the ridge cut line

1. From the ridge cap, measure down 1.5-2 inches from the peak on both sides
2. Snap a chalk line - this is your cut line for the slot
3. The slot will be 3 inches wide total (1.5 inches each side of peak)
4. Stop the slot 6-12 inches short of each gable end (don't vent into gable wall)

Step 3: Remove ridge cap shingles

1. Pry up the ridge cap shingles + remove
2. Save undamaged ones for reuse on the gable ends
3. Pry up the underlayment + shingles below the cap on both slopes (where the slot will be cut)

Step 4: Cut the slot

1. Set saw blade depth to deck thickness (1/2" - 3/4")
2. Cut along chalk lines on both sides of peak
3. Remove the deck strip
4. The slot opens through the entire ridge length (where marked)
5. Vacuum out wood chips + debris

Step 5: Install ridge vent

1. Roll out ridge vent material along the entire ridge
2. Snap or screw fit per manufacturer (some are roll-on; others are panel-by-panel)
3. Overlap pieces per manufacturer spec
4. Fasten through both flanges + into deck (NOT through the vent's mesh; that compresses)
5. End caps on each end of the ridge

Step 6: Install ridge cap over vent

1. Re-install underlayment OVER the ridge vent flanges
2. Install starter ridge cap at one end
3. Install ridge cap shingles over the ridge vent
4. Use longer nails (2.5"+ to penetrate vent + deck adequately)
5. Caulk end caps + any cut shingles

Step 7: Verify + close out

1. Inspect from inside attic - air movement detectable at ridge
2. Photo the completed ridge
3. Customer briefing: explain how ventilation works + benefits

Common mistakes

• No soffit vents: ridge vent without intake pulls air from house, increases AC load
• Slot too narrow: 3" total is standard; narrower restricts airflow
• Slot too long: extending to gable ends creates wind-driven rain entry
• Wrong nail length: short nails don't anchor adequately
• Combining ridge vent + box vents on same roof: short-circuits airflow; box vents become intake instead of exhaust
• Combining ridge vent + gable vents: same short-circuit problem
• Damaging ridge vent during cap install: fasteners through mesh compress + reduce airflow

Net free ventilation calculation

Required: 1 sq ft of NFV per 150 sq ft attic floor.

Example 1,500 sq ft attic = 10 sq ft total NFV needed = 5 sq ft intake + 5 sq ft exhaust.

Ridge vent NFV varies by product: 12-18 sq inches per linear foot. So 5 sq ft = 720 sq inches. At 14 sq in/ft, you need ~52 linear feet of ridge.

Most ranch-style homes have 35-45 ft of ridge. Coupled with box vents OR turbine vents to make up the deficit.

For larger attics OR steeper roofs: turbine or powered fan needed in addition to ridge vent.

Combining ventilation strategies

Compatible:

• Ridge vent + soffit vents = ideal
• Ridge vent + gable vents = NO (gable vents short-circuit ridge airflow)
• Ridge vent + box vents = NO (box vents short-circuit)
• Ridge vent + turbine = OK if soffit intake adequate

Powered ventilation:

• Solar-powered roof vents (no electrical run): nice add-on
• Powered fans: only if natural ventilation is inadequate; can pull conditioned air from house

Customer benefits to articulate

• Shingle warranty: most manufacturers require balanced ventilation
• Energy: 5-10% lower cooling bills
• Roof life: 5-10 years longer (lower heat exposure)
• Moisture: prevents attic condensation + mold
• Ice damming: ventilation prevents warm spots at eaves

References

• NRCA ventilation guidelines
• ASHRAE attic ventilation research
• IRC R806 (residential ventilation requirements)
• Manuall internal: Asphalt Shingle Roof Replacement SOP, Residential Roof Inspection SOP