Attic Ventilation & Insulation: what to expect
Air sealing comes before insulation
Insulation slows heat conduction; it does not stop air moving. Warm, moist indoor air rising through recessed light housings, plumbing chases, wiring penetrations, the top plates of interior walls and an unweatherstripped attic hatch carries both heat and moisture straight to the underside of the roof deck. Adding insulation over unsealed penetrations gets you a fraction of what you paid for. Seal first, then insulate.
Ventilation is a system, not a vent
Balanced ventilation means intake low and exhaust high: continuous soffit intake, an unobstructed path over the insulation, and ridge exhaust. The most common defect in Connecticut attics is soffit vents packed shut with insulation, which leaves ridge vents pulling conditioned air out of the house instead of outdoor air across the deck. Baffles at the eaves keep that channel open. Mixing exhaust types, a ridge vent plus gable vents plus a powered fan, can also short-circuit the airflow.
What it buys you
A cold, dry, well-ventilated deck stops snow melting from below, which is what ends the ice dam cycle. It also keeps summer attic temperatures down, which slows shingle ageing, and it removes the moisture that condenses on nail tips and grows mould on sheathing. It is generally cheaper than the annual ice dam call, and it is work worth doing at the same time as a re-roof while the deck is open.
Typically included
- Attic-floor air sealing at penetrations and top plates
- Weatherstripped and insulated attic hatch
- Insulation levelled to consistent depth out to the eaves
- Soffit intake, eave baffles and ridge exhaust balanced
- Bath and kitchen fans ducted through the roof, not into the attic
- Moisture, frost and mould assessment on the sheathing