How to Inspect the Building Exterior to Detect & Correct Attic Condensation and Ice Dam Leaks in buildings

How to Inspect the Building Exterior for Wet Site, Sources of Attic Condensation, Moisture, & Roof Venting Problems & Attic Mold
- How to detect roof venting deficiencies, attic insulation defects, and attic condensation problems
Questions & Answers about attic moisture, condensation & ventilation: how to spot roof venting problmes from outside the building
References

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This article 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.

Also see CATHEDRAL CEILING INSULATION and Roof Venting: Eaves Intake if no Overhang. The photograph shown at the top of this page offers compelling evidence of roof leaks into the soffit of this older home. This article is part of the series Roof Venting: Correct Inadequate and part of our discussion of ATTIC CONDENSATION CAUSE & CURE.

A Photo Guide for Inspecting the Building Exterior for Wet Site, Sources of Attic Condensation, & Roof Venting Problems

Here we provide a series of photographs taken of the exterior of buildings, demonstrating visual clues that can predict a problem with ice dam leaks into these homes.

No Soffit Intake Vents on a Roof Means Ice Dams

In freezing climates, as in our photograph at page top, given the age of construction (pre 1900), the brown color of the stains (oils from roof sheathing boards that have been wet), and the shape of the roof edge (probably there was a built-in eaves trough gutter), it is likely that when we inspect the attic interior we'll see that despite the perforated soffit covers, the roof has no intake venting and there has been a long history of ice dam leaks on this building.

Inadequate soffit or ridge venting risks attic moisture, mold, ice dams, as show by these photos

In both heating and cooling climates, insufficient roof ventilation risks attic or roof cavity condensation, mold, rot, and in some cases increased heating or cooling costs for the building. And as we show just below, do not assume that your building has working roof ventilation even if you see perforated panels covering the building soffit underside

Fake Soffit Vents?

Too often building exterior renovations include covering an existing, solid, un-vented building soffit or eaves with perforated panels, forming a "faux vent" system since the perforations are not really passing any air into the building attic.

It's easy to spot this condition both by visual inspection and, where accessible, by pressing on the perforated panels - if they are over an open space they will move easily.

In our photograph at left, although perforated panels are installed on soffits of this older home, we see extensive leak stains on that material. From outside we posit that either the perforated panels were installed over solid wood - there is no actual soffit intake venting for the attic, or the building simply has little or no attic insulation, resulting in lots of heat loss into the attic during winter months, combined with freezing of melting snow at the colder roof edges.

No Soffits so No Soffit Vents Means Ice Dams and Wall Leaks are Likely

The home shown in our photograph at left was built with no roof overhang whatsoever - or no roof soffits or eaves extension past the building walls. Not only does roof runoff too often run down the exterior wall surface, inviting rot or insect damage or wall leaks, but also this construction makes it tricky to obtain any roof cavity intake venting.

Special products such as the Hicks (TM) starter vent can be used at roof eaves in this location, but an air path must also be provided inside under the roof decking.

The window at the building right corner tells us that cathedral ceilings were probably installed inside this home - under-roof venting would still be a good step to avoid roof cavity condensation, leaks, mold, or related damage.

See Roof Venting: Eaves Intake if no Overhang for some suggestions on how to vent this design.

Tiny Gable End Vents can Predict Ice Dams and Inadequate Attic Ventilation on buildings

Gable end vent in a building wall - photo

The photograph shown at left demonstrates a tiny gable-end vent in an older building.

This home combines stone construction, multiple shingle layers, shaded site with (unseen) no other attic intake or outlet ventilation, to make attic condensation problems and seasonal ice dam leaks likely.

Photographs of Building Siding Stains Can Indicate Ice Dam Leaks

This photo shows siding stains caused by roof ice dam leaks into the wall cavity. Notice that the soffit is un-vented on this older home. Roof leaks into the wall cavity have run down the walls and exited between clapboards, leaving stains and peeling paint.

Roof leaks in this area from any cause, ice dams or work, leaky roofing materials will all produce this effect.

Photos of Use of Heating Tapes on Roof Edges Tells the Ice Dam Story

This photo shows roof edge heating tapes installed by an owner to attempt to melt channels through ice that may accumulate at the roof eaves in winter. This is an inexpensive band-aid that may be sufficient if ice dam formation on a roof is rare and/or it is difficult to install good under-roof venting.

This roof has eaves and a ridge that could have been vented.

If a roof shape prevents easy installation of under-roof venting, or if a home is located where building custom excludes under-roof venting, use of an ice-and-water shield product under the shingles at roof edges, or use of metal covering the lower roof slopes are other measures taken to prevent ice dam leaks into the building interior.

See HEAT TAPES & CABLES on Roofs for Ice Dams
for details about the use of heating cables on roofs to prevent ice dam leak damage.

Signs of Roof Ice Dam Problems Can Be Seen in Any Season

In addition to our photos showing missing roof intake or outlet venting, roof leak stains, and similar clues, you may be able to spot evidence of attempts to remove roof ice dams by chopping at the ice itself.

Usually attempts to remove roof ice by chopping at it results in damaged roof shingles and sometimes holes in nearby flashing or gutters as shown in this photo.

You'll also spot chop or cut marks in roof shingles at the lower roof edges when this procedure has been attempted.

A Summary of Inspection Tips for Roof Venting & Ice Dam Problems

Missing snow on this cape shows where there is missing or poor insulation and/or no under-roof venting.

The first signs of a probable attic condensation problem may there for observation before even entering a building.

Look at the roof. If you're in a cold climate during winter months you may see areas of snow-melt showing where there is an insulation defect. Or you may see actual severe ice dams at the roof eaves. If the shingles are exposed look for signs of attic moisture in their condition: if there is a high level of attic moisture, unless the roof is quite young, you might see puckered shingles in the classic "fishmouth" pattern.

This shingle curling is quite obvious. If you inspect the exterior roof surface first, on an old roof you'll note shingles which are brittle and which may crack or break. (Don't walk on such surfaces.) If the roof sheathing is plywood, you may sense surface deflection which could simply be thin 3/8" plywood (no longer permitted in most jurisdictions) or it could be damaged from heat or moisture. (Beware of falling through).

Look at the ridge. If there is no ridge vent there is no good outlet for an under-roof attic venting system and this roof will be difficult to ventilate. When you make your inside inspection you will also inspect the roof below any "apparent" ridge vents seen outside, as sometimes we find that a faux ridge vent was installed with no openings cut into the roof cavity. See Inspect the Ridge Vent System from the Attic.
Look at the eaves or soffits. If there are no continuous intake vents at the soffits, this roof will be difficult to ventilate. And when you make your inside inspection you will look for light or other indications that the eave or soffit vents you found are real, not faux. See Inspect Attics for Moisture or Mold.
Look at the roof lines. If the building has no roof overhang, flat roofs, low-slope roofs, roofs abutting Building walls, or complex roof lines, these roofs will be difficult to ventilate. See Roof Venting: Eaves Intake if no Overhang and Roof Venting: Un-Vented Hot Roof Solutions.

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

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. (727) 595-4211 mark@BestTampaInspector.com 11/06 & 12/08
John Annunziata, P.E. - NY Metro ASHI during informal chapter discussions about roof and attic ventilation options (1986-1996).
The Smart Vent™ by DCI roof intake venting provides an intake at the lower edge of roof decking for difficult cases. See www.dciproducts.com/html/smartvent.htm
The AccuVent™ attic ventilation roof baffle produced by Berger permits insulation to extend over the top plate as far forward as possible. See www.bergerbuildingproducts.com/pdfs/AccuVentAtticVent.pdf
GAF Cobra® and other GAF roof ventilation products: see www.gaf.com/Content/GAF/RES1/ROOF/RS_whyuse_ventchart.asp?viewer=&module=
Humidity: What indoor humidity should we maintain in order to avoid a mold problem?
Mold-Resistant Building Practices, advice from an expert on how to prevent mold after a building flood and how to prevent mold growth in buildings by selection of building materials and by anti-mold construction details.
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
[1] Air Vent, Inc., Tel: 1-800-247-8368, Email: ventilation@gibraltar1.com, web search 08/11/11,
[2] National Roofing Contractors Association, NRCA, 10255 W. Higgins Road Suite 600 Rosemont, IL 60018-5607 Telephone: (847) 299-9070, web search 08/11/11,
[3] Hicks Starter Vent, and Smart Vent, see Roof Venting: Eaves Intake if no Overhang
[4] Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education. Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
"Minimizing Air Leakage in Log Homes"
"Controlling Moisture in Log Homes" and the more general (but brief) DOE article series on moisture control:
- "Moisture Control", U.S. DOE
- "Moisture Control in Basements", U.S. DOE
- "Crawl Space Moisture Control", U.S. DOE
- "Slab-on-Grade Foundation Moisture and Air Leakage Control", U.S. DOE
- "Moisture Control in Walls", U.S. DOE
Humidity: What indoor humidity should we maintain in order to avoid a mold problem?
"Ventilation", U.S. DOE, describes the purpose of building ventilation and three basic ventilation strategies:
- Natural house ventilation methods
- Whole House Ventilation Methods, including exhaust ventilation methods, supply ventilation of buildings, balanced building ventilation, and energy recovery (heat exchanger) ventilation systems
- Spot Ventilation in buildings
"Weather-Resistive Barriers [copy on file as /interiors/Weather_Resistant_Barriers_DOE.pdf ] - ", how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
"Vapor Barriers or Vapor Diffusion Retarders", U.S. DOE: how vapor barriers work, types of vapor diffusion barriers, installing vapor barriers
ASHRAE resource on dew point and wall condensation - see the ASHRAE Fundamentals Handbook, available in many libraries. The following three ASHRAE Handbooks are also available at the InspectAPedia bookstore in the third page of our Insulate-Ventilate section:
- 2005 ASHRAE Handbook : Fundamentals : Inch-Pound Edition (2005 ASHRAE HANDBOOK : Fundamentals : I-P Edition) (Hardcover), Thomas H. Kuehn (Contributor), R. J. Couvillion (Contributor), John W. Coleman (Contributor), Narasipur Suryanarayana (Contributor), Zahid Ayub (Contributor), Robert Parsons (Author), ISBN-10: 1931862702 or ISBN-13: 978-1931862707
- 2004 ASHRAE Handbook : Heating, Ventilating, and Air-Conditioning: Systems and Equipment : Inch-Pound Edition (2004 ASHRAE Handbook : HVAC Systems and Equipment : I-P Edition) (Hardcover)
  by American Society of Heating, ISBN-10: 1931862478 or ISBN-13: 978-1931862479
  "2004 ASHRAE Handbook - HVAC Systems and Equipment The 2004 ASHRAE HandbookHVAC Systems and Equipment discusses various common systems and the equipment (components or assemblies) that comprise them, and describes features and differences. This information helps system designers and operators in selecting and using equipment. Major sections include Air-Conditioning and Heating Systems (chapters on system analysis and selection, air distribution, in-room terminal systems, centralized and decentralized systems, heat pumps, panel heating and cooling, cogeneration and engine-driven systems, heat recovery, steam and hydronic systems, district systems, small forced-air systems, infrared radiant heating, and water heating); Air-Handling Equipment (chapters on duct construction, air distribution, fans, coils, evaporative air-coolers, humidifiers, mechanical and desiccant dehumidification, air cleaners, industrial gas cleaning and air pollution control); Heating Equipment (chapters on automatic fuel-burning equipment, boilers, furnaces, in-space heaters, chimneys and flue vent systems, unit heaters, makeup air units, radiators, and solar equipment); General Components (chapters on compressors, condensers, cooling towers, liquid coolers, liquid-chilling systems, centrifugal pumps, motors and drives, pipes and fittings, valves, heat exchangers, and energy recovery equipment); and Unitary Equipment (chapters on air conditioners and heat pumps, room air conditioners and packaged terminal equipment, and a new chapter on mechanical dehumidifiers and heat pipes)."
- 1996 Ashrae Handbook Heating, Ventilating, and Air-Conditioning Systems and Equipment: Inch-Pound Edition (Hardcover), ISBN-10: 1883413346 or ISBN-13: 978-1883413347 ,
  "The 1996 HVAC Systems and Equipment Handbook is the result of ASHRAE's continuing effort to update, expand and reorganize the Handbook Series. Over a third of the book has been revised and augmented with new chapters on hydronic heating and cooling systems design; fans; unit ventilator; unit heaters; and makeup air units. Extensive changes have been added to chapters on panel heating and cooling; cogeneration systems and engine and turbine drives; applied heat pump and heat recovery systems; humidifiers; desiccant dehumidification and pressure drying equipment, air-heating coils; chimney, gas vent, fireplace systems; cooling towers; centrifugal pumps; and air-to-air energy recovery. Separate I-P and SI editions."
- Principles of Heating, Ventilating, And Air Conditioning: A textbook with Design Data Based on 2005 AShrae Handbook - Fundamentals (Hardcover), Harry J., Jr. Sauer (Author), Ronald H. Howell, ISBN-10: 1931862923 or ISBN-13: 978-1931862929
- 1993 ASHRAE Handbook Fundamentals (Hardcover), ISBN-10: 0910110964 or ISBN-13: 978-091011096
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.
Energy Savers: Whole House Systems Approach to Energy Efficient Home Design [copy on file as /interiors/Whole_House_Energy_Efficiency_DOE.pdf ] - U.S. Department of Energy
"Energy Savers: Whole-House Supply Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Supply_Vent.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11880?print
"Energy Savers: Whole-House Exhaust Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Exhaust.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11870
"Energy Savers: Ventilation [copy on file as /interiors/Energy_Savers_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Natural Ventilation [copy on file as /interiors/Energy_Savers_Natural_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Energy Recovery Ventilation Systems [copy on file as /interiors/Energy_Savers_Energy_Recovery_Venting.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11900
"Energy Savers: Detecting Air Leaks [copy on file as /interiors/Energy_Savers_Detect_Air_Leaks.pdf ] - ", U.S. Department of Energy
"Energy Savers: Air Sealing [copy on file as /interiors/Energy_Savers_Air_Sealing_1.pdf ] - ", U.S. Department of Energy
Ice Dam Leaks in building attics and roof cavities, how to inspect for evidence of leaks, identify causes, and correct bad attic ventilation, improper roof venting, and these causes of attic mold or roof structure damage

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

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.

"Energy Savers: Whole-House Supply Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Supply_Vent.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11880?print
"Energy Savers: Whole-House Exhaust Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Exhaust.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11870
"Energy Savers: Ventilation [copy on file as /interiors/Energy_Savers_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Natural Ventilation [copy on file as /interiors/Energy_Savers_Natural_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Energy Recovery Ventilation Systems [copy on file as /interiors/Energy_Savers_Energy_Recovery_Venting.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11900
"Energy Savers: Detecting Air Leaks [copy on file as /interiors/Energy_Savers_Detect_Air_Leaks.pdf ] - ", U.S. Department of Energy
"Energy Savers: Air Sealing [copy on file as /interiors/Energy_Savers_Air_Sealing_1.pdf ] - ", U.S. Department of Energy
Humidity: What indoor humidity should we maintain in order to avoid a mold problem?
Mold-Resistant Building Practices, advice from an expert on how to prevent mold after a building flood and how to prevent mold growth in buildings by selection of building materials and by anti-mold construction details.
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