Attic ventilation with a new roof

Short answer: a new roof is the easiest time to fix how the attic breathes. Balanced airflow, in at the eaves and out at the ridge, keeps shingles from baking in summer and keeps the decking dry in winter.

How a vented attic works

Cool air comes in low, through soffit vents or a vented drip edge. Warm, moist air goes out high, usually through a continuous ridge vent. The building code calls for a balance between the two. If the intake is blocked, the exhaust pulls air from wherever it can, including warm, damp air from the rooms below.

Why it matters in Connecticut

Winter

Through a Hartford winter, warm indoor air leaks into the attic around lights, pipes and the hatch. It meets cold roof boards and turns to frost or water. Over several winters that stains and softens the decking and feeds mold. Heat in the attic also melts roof snow, which refreezes at the eaves as ice dams. See will a new roof stop ice dams.

Summer

A sealed attic in July can get far hotter than the air outside. That heat ages asphalt shingles from below and pushes into top-floor bedrooms.

Signs your attic cannot breathe

• Frost on nail tips on cold mornings
• Dark stains or growth on the underside of the roof boards
• Damp or flattened insulation
• Insulation packed against the eaves, covering the soffits
• Bath fans that empty into the attic
• Ice dams along the same eaves every year

What can change during a replacement

1. Ridge vent. A slot cut along the peak, covered by a low vent cap.
2. Old vents closed. Box vents, turbines or gable fans left beside a ridge vent can short-circuit the airflow. They are removed and patched.
3. Intake opened. Painted-over soffits are cleared or new soffit vents added, with baffles to hold insulation back from the eaves.
4. Damaged decking replaced before the new underlayment goes down.

Capes, kneewalls and finished attics

Many Cape Cods in Newington, Wethersfield and Rocky Hill have finished upstairs rooms with kneewalls and sloped ceilings. The roof over those rooms often has only a narrow channel between the insulation and the deck, or none at all. Those roofs need a specific plan, such as vent baffles in each rafter bay or insulation added above the deck. Ask the contractor how they will handle it.

Questions to ask the roofer

• Will you inspect the attic before the job, and what did you find?
• How will intake and exhaust be balanced?
• Which existing vents will be closed off?
• Will baffles go in at the eaves?
• What does the shingle maker require for ventilation on this product?

For the rest of the job, see what happens on roof replacement day.