SKYLIGHT VENTILATION DETAILS - CONTENTS: How to ventilate a roof cavity below and around a skylight. How to Correct Inadequate Attic Venting to Stop Attic Condensation, Ice Dam Leaks, Attic Mold, & Roof Structure Damage
Roof Ventilation Details at Skylights to Provide an Air Path - Eaves to Ridge
This article series describes inspection methods and clues to detect roof venting deficiencies, insulation defects, and attic condensation problems
in buildings. It describes proper roof ventilation placement, amounts, and other details.
These recommendations are based on a survey of building science literature combined with 30 years of
building inspections, on the observation of the locations of moisture, mold, ice dams, condensation stains, and other clues in buildings,
and on the correlation of these clues with the roof venting conditions at those properties.
We have measured very large changes in airflow, temperature,
and moisture before and after installing roof venting.
Localized hot spots such as skylights can
also lead to ice dams below, due to blocked ventilation as
well as melt water from skylight heat loss.
rafters on either side of the skylight will help maintain airflow
above the skylight (Figure 2-59 at left).
If icing on your skylight window interior surface in winter is still a problem, add an interior storm window
to reduce heat loss through the glass in cold weather.
As a backup to prevent leaks at skylights, during skylight installation and even though modern skylights are usually provided with a factory-built flashing and counterflashing, it is always a good idea to seal the skylight
curb and surrounding roof area with a bituminous membrane
(see Figure 2-5 at left).
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"Unvented Roofs, Hot-
Humid Climates, and
Asphalt Roofing Shingles
Research Report - 0306
Building Science Corporation", Building Science Corporation, 30 Forest Street,
Somerville, MA 02143 Quoting from the article abstract:
"When constructing unvented roofs with asphalt shingles in hot-humid climates, a vapor barrier must be
installed between the asphalt shingles and the roof deck." - Web Search 5/21/2010
Thanks to reader - Mike Martino for discussing attic ventilation retrofit ideas - August 2010
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