Wet insulation below vents

Insulation · Attics · printed page 248 (PDF page 249)

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WIND
snow (or rain) gets sucked in through the windward roof vent
air flow
roof vent
roof rafter
insulation
compressed and/or wet insulation (especially noticeable with cellulose insulation)
soffit vents not performing adequately
wall
note:
if there are roof vents only on the windward side, snow and rain are more likely to enter the attic
cross section

Generated explanation

A cross section of a pitched roof and attic shows wind driving snow or rain into a windward roof vent. Airflow arrows show entry through that vent and exhaust through a vent on the opposite roof slope. Precipitation falls onto the attic-floor insulation, where a localized depression is labeled as compressed and/or wet insulation, especially noticeable with cellulose. The soffit vents are identified as not performing adequately. A note warns that snow and rain are more likely to enter the attic if roof vents are located only on the windward side.

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Wet insulation below vents

· p. 246

The cross section shows an attic beneath a pitched roof, with roof vents on both slopes and insulation over the ceiling. Wind and airflow arrows show snow or rain being drawn through the windward roof vent and falling on