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This roof ventilation and ice dam leak prevention article compares Two Identical Houses, With and Without Roof Ventilation and Insulation to Understand Attic Moisture Problems. Both homes, located in "the Bleachery" in Wappingers Falls, NY were built in the late 1800's overlooking Wappingers Lake.

This article is part of our roof ventilation & attic condensation article series. These articles describe 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. The photograph at page top shows the author's introduction to roof ice dams at 25 King Drive in Poughkeepsie, NY in 1970.

© Copyright 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website.

Comparing Two Identical Houses, With and Without Roof Ventilation and Insulation to Understand Attic Moisture Problems

One of these pre-1900 homes (at below left) was renovated by the author (DJF) to include effective soffit intake and ridge exhaust under-roof venting along wtih insulation and air leak sealing throughout the structure. The second home (below right) had a drafty attic that had avoided attic condensation and moisture troubles but the design sucked so much heat out of the home in winter that combined with little attic insulation the house suffered from extensive ice dam formation.

On two identical 1860's Wappingers Falls NY "Bleachery" historic houses shown in these photos, the one with no melted snow was renovated to include continuous soffit and ridge venting and good attic insulation. Look at the difference in the two roofs on the same winter day. These homes, located on West Street in the village of Wappingers Falls, New York, were built to house workers at nearby mills powered by water from Wappingers Creek. When the homes were built they lacked central heating, storm windows, siding, caulking, and insulation. They were drafty. Interior moisture and condensation were less likely to damage the structure than today, nearly 130 years later, when the energy improvements listed have been added to the homes, making them tighter but also providing indoor moisture sources such as from bathing or cooking. The house whose roof shows melted snow and bare roof slates (beware of nasty owner) has inadequate venting and inadequate insulation, giving rise to snow melt and ice damming, and almost certainly to attic condensation and moisture. The house whose roof is covered with a uniform blanket of un-melted snow, (renovated by the author) was improved to add attic insulation in the attic floor as well as continuous soffit intake venting and ridge outlet venting. After these vents were added we also closed-off the gable end vents (not shown) to assure that airflow moved over the desired pathway. The builders of this house had blocked the soffits with boards on edge between each rafter pair in an effort to "warm up" the cold attic. We removed these blocking boards to assure a proper airflow.

Global warming and building ice dam leaks? Venting of roof cavities helps reduce the effects of hot weather associated with global warming

In a 1996 version of this article in the Journal of Light Construction we paraphrased Stephen Jay Gould, a Harvard scholar who said "The world is currently enjoying a brief warm spell in the midst of a basically cool period.

Gould said that the glaciers that covered our region might return in another 10,000 years or so. We added that the sheets of ice we see creeping down buildings in freezing climates are not due to global freezing but due to poor building ventilation and insulation.

That conservative view of climate change has since proven to be mistaken, as very rapid global warming is, in 2008, a fact accepted by virtually every qualified scientist. But global warming does not mean that we can blithely ignore attic ventilation. Not only will the risk of ice dam leaks continue to occur on poorly-insulated and poorly-ventilated building roofs, but more, the benefits of proper under-roof ventilation are present in hot weather as well.

A properly ventilated building roof cavity or attic means that the roof surface as well as the attic will be cooler in hot weather, reducing indoor cooling costs and extending the life of the roof covering.

Questions & Answers regarding this article

Questions & answers about methods for preventing ice dam leaks and ice formation on roof edges

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Technical Reviewers & References

• InspectAPedia.com^® - Daniel Friedman - Publisher & Editor.
• Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
• Alan Carson Carson Dunlop Associates, Toronto, Ontario. Mr. Carson is a home inspection professional, educator, researcher, writer, and a principal of Carson Dunlop Associates, a Toronto home inspection and education firm. Mr. Carson is a past president of ASHI, the American Society of Home Inspectors Some great illustrations of the proper under-roof ventilation pathways are offered by Carson Dunlop
• . 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
• Daniel Friedman - principal author Daniel Friedman, editing, expanding, adding to comments from John Annunziata, P.E. - NY Metro ASHI informal chapter discussions. A version of this material was published as "Case in Point: The Ice Dam Cometh, Dan Friedman, Journal of Light Construction, NE8/JLC February 1996 p. 8.
• Technical reviewers are invited to comment or ask questions - contact us

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

ATTIC LEAKS, CONDENSATION & ATTIC MOLD
  Air Bypass Leaks, Thermal Tracking
  Blocked Soffit Intake Vents
  CATHEDRAL CEILING INSULATION
  CATHEDRAL CEILING VENTILATION
  Comparing Two Houses
  Heat Tapes: Use on Roofs for Ice
  HEAT TAPES & CABLES on Roofs for Ice Dams
  HOT ROOF DESIGNS: Un-Vented Roof Solutions
  HOUSEWRAP AIR & VAPOR BARRIERS
  HUMIDITY LEVEL TARGET
  ICE DAM PREVENTION
  ICE DAM CURE: Comparing Two Houses
  Inspect Attics for Moisture or Mold
  Inspect Attics for Blocked Soffit Intake Vents
  Inspect Basements for Moisture or Mold
  Cold Pour Joint Leaks
  Form Tie Leaks
  Wall Crack Leaks
  Floor-Wall Joint Leaks
  Inspect Building Exterior - Roof Venting
  Inspect the Ridge Vent System from the Attic
  Inspect the Soffit Vent System from the Attic
  ROOF VENTILATION SPECIFICATIONS
  Roof Venting: Intake - Outlet Area Ratios
  Roof Venting: Proper Locations
  Roof Venting: Both Ridge & Eaves Venting Needed
  Roof Venting: Eaves Intake if no Overhang
  Roof Venting: Soffit Intake Vent-Continuous
  Roof Venting: Un-Vented Hot Roof Solutions
  ROOF VENTING ENERGY SAVING DETAILS
  ROOF VENTING NEEDED?
  SKYLIGHT VENTILATION DETAILS
  Soffit Ventilation

ATTIC VENTILATION

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 Elimination of Unsafe Guardrails, a Progress Report," Elliott O. Stephenson, Building Standards, March-April 1993
• "Are Functional Handrails Within Our Grasp" Jake Pauls, Building Standards, January-February 1991
• Access Ramp building codes:
  • UBC 1003.3.4.3
  • BOCA 1016.3
  • ADA 4.8.2
  • IBC 1010.2
• Access Ramp Standards:
  • ADA (Americans with Disabilities Act), Public Law 101-336. 7/26/90 is very often cited by other sources for good design of stairs and ramps etc. even where disabled individuals are not the design target.
  • ANSI A117.4 Accessible and Usable buildings and Facilities (earlier version was incorporated into the ADA)
  • ASTM F 1637, Standard Practice for Safe Walking Surfaces, (Similar to the above standards)
• "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
• Falls and Related Injuries: Slips, Trips, Missteps, and Their Consequences, Lawyers & Judges Publishing, (June 2002), ISBN-10: 0913875430 ISBN-13: 978-0913875438
  "Falls in the home and public places are the second leading cause of unintentional injury deaths in the United States, but are overlooked in most literature. This book is unique in that it is entirely devoted to falls. Of use to primary care physicians, nurses, insurance adjusters, architects, writers of building codes, attorneys, or anyone who cares for the elderly, this book will tell you how, why, and when people will likely fall, what most likely will be injured, and how such injuries come about. "
• Humidity: What indoor humidity should we maintain in order to avoid a mold problem?
• Slips, Trips, Missteps and Their Consequences, Second Edition, Gary M. Bakken, H. Harvey Cohen,A. S. Hyde, Jon R. Abele, ISBN-13: 978-1-933264-01-1 or ISBN 10: 1-933264-01-2, available from the publisher, Lawyers ^ Judges Publishing Company,Inc., www.lawyersandjudges.com sales@lawyersandjudges.com and also from the InspectAPedia Bookstore (Amazon.com)
• The Stairway Manufacturers' Association, (877) 500-5759, provides a pictorial guide to the stair and railing portion of the International Residential Code. [copy on file as http://www.stairways.org/pdf/2006%20Stair%20IRC%20SCREEN.pdf ] -
• What Mold and Allergens Look Like: mold identification photos to help identify mold - choosing what to sample in buildings
• How to Clean Moldy Wood Framing & Sheathing How to clean/seal mold from/on exposed lumber or plywood subfloor or roof sheathing indoors - some suggestions based on our field and laboratory research
• Lighting, proper use of: proper aiming of a good flashlight can disclose hard to see but toxic light or white mold colonies on walls.
• Mold spores in the Home - a Photo ID Library for detection and identification of mold allergens.
• How to Find and Test For Mold in buildings A "how to" photo and text primer on finding and choosing the right spots to test for mold in buildings
• Stuff that is not mold but is often mistaken for it - things you may not want to test. Also, not all "black mold" is toxic - here are examples of harmless black mold.
• Simple Adhesive Tape Sampling of Moldy Surfaces - how to send a mold sample to our lab
• Mold Sampling Methods in the Indoor Environment - In-depth article: detailed critique of popular mold testing methods - Is your mold test kit worth the bother?
• 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.
• Slips, Trips, Missteps and Their Consequences, Gary M. Bakken, H. Harvey Cohen, Jon R. Abele, Alvin S. Hyde, Cindy A. LaRue, Lawyers and Judges Publishing; 2 edition (April 2006), ISBN-10: 1933264012 ISBN-13: 978-1933264011
• Steps and Stairways, Cleo Baldon & Ib Melchior, Rizzoli, 1989.
• The Staircase, Ann Rinaldi
  
• Common Sense Stairbuilding and Handrailing, Fred T. Hodgson
• The Art of Staircases, Pilar Chueca
• Building Stairs, by pros for pros, Andy Engel
• A Simplified Guide to Custom Stairbuilding, George R. Christina
• Basic Stairbuilding, Scott Schuttner
  
• The Staircase (two volumes), John Templar, Cambridge: the MIT Press, 1992
• The Staircase: History and Theories, John Templar, MIT Press 1995
• Steps and Stairways, Cleo Baldon & Ib Melchior, Rizzoli, 1989.
• "The Dimensions of Stairs", J. M. Fitch et al., Scientific American, October 1974.
• "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
• 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.
• Decks and Porches, the JLC Guide to, Best Practices for Outdoor Spaces, Steve Bliss (Editor), The Journal of Light Construction, Williston VT, 2010 ISBN 10: 1-928580-42-4, ISBN 13: 978-1-928580-42-3, available from Amazon.com
• ...