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 Roof Ventilation Details for Skylights
- 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
- Questions & Answers about how to get roof ventilation working around skylights.
- References
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InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
This article explains How to Correct Improper or Inadequate Attic or Under-Roof Ventilation at skylights, This article on the design of proper venting around roof skylights is part of our series of articles about ATTIC CONDENSATION CAUSE & CURE.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
Roof Ventilation Details at Skylights to Provide an Air Path - Eaves to Ridge
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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.
See CATHEDRAL CEILING VENTILATION, and also see VENTILATION in BUILDINGS and INSULATION LOCATION - WHERE TO PUT IT. And see COOLING LOAD REDUCTION by ROOF VENTS.
As described in Best Practices Guide to Residential Construction:
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.
Notching the
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.
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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).
Also see SKYLIGHT LEAK DIAGNOSIS & REPAIR and see Skylight Glass Breakage.
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Also see Ice Dam Protection for Skylignts for cases where under-roof venting is not provided around a skylight.
Cathedral Ceiling Ventilation Alongside of Skylights
Cathedral ceilings require the same continuous air barriers,
and balanced soffit and ridge vents, as attics.
Both air
sealing and ventilation are more critical, however, since
any trapped moisture in the roof cavity will remain longer
and potentially cause greater damage than in an open attic.
Also, since there is little or no communication from bay to
bay, an effective ventilation system must reach every bay
(Figure 2-57 at left).
Details about cathedral ceiling ventilation are at CATHEDRAL CEILING VENTILATION. Also see CATHEDRAL CEILING INSULATION. |
-- Adapted with permission from Best Practices Guide to Residential Construction.
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
- Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Amazon.com and also Wiley.com. See our book review of this publication.
 Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
- Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
- Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
- Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference Book, a reference & inspection report product for building owners & inspectors.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
- The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.
Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
- The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
- Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
- "Unvented Roofs, Hot-
Humid Climates, and
Asphalt Roofing Shingles
Research Report - 0306
Feb-2003
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
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
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