Window Condensation: Cause, Cure, Prevention, Resistance Ratings
|
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
Window condensation problem troubleshooting & repair: this article discusses problems with excessive condensation on windows and skylights and reviews the causes and cures of window condensation, secondary effects (mold, rot, decay), and also the condensation resistance of window glazing materials.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
Condensation Resistance Ratings for Windows: Window Condensation or "Sweating"
In this article series we discuss the selection and installation of windows and doors, following best construction and design practices for building lighting and ventilation, with attention to the impact on building heating and cooling costs, indoor air quality, and comfort of occupants. We review the proper installation details for windows and doors, and we compare the durability of different window and door materials and types. This article includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons.
See WINDOWS & DOORS our home page for window and door information. Ourlinks listed at Related Topics provide in-depth articles on window and door selection, inspection, installation, problem diagnosis, and repair.
To rate a window’s resistance to condensation, NFRC recently
developed a method that evaluates the window’s
frame, glass, and glass edge at a standardized set of temperature
and humidity conditions.
Based on the coldest
part of the window assembly, it is assigned a rating from
1 to 100.
The higher the rating, the better the window is at
resisting condensation, but the rating doesn’t predict condensation
under specific conditions. The voluntary minimum
for a “thermally improved window” under the
AAMA/NWWDA standard is 35.
The best protection against condensation is low-E
glass with gas fill, combined with warm-edge spacers and
a nonmetallic window frame, such as wood, vinyl, fiberglass,
or one of the newer composites. Table 3-6 (below) provides
a general guide to when condensation is likely to form on
different types of glazing. Without warm-edge spacers,
condensation will occur at window edges first.
(Also see CONDENSATION or SWEATING PIPES, TANKS and DEW POINT TABLE - CONDENSATION POINT GUIDE as well as HUMIDITY LEVEL TARGET.)
How to Avoid Condensation Problems on Skylight Windows
Because warm moist air is carried upward
by convection currents, skylights are often one of the
first places to develop condensation. This can lead to dripping
and staining of the frame, well, or furnishings below.
The best defense against skylight condensation is to choose high
R-value glazing with warm-edge spacers. Good insulation
of the skylight well also helps by keeping the surrounding
area warmer. Several manufacturers offer skylights with
integral condensation gutters, a helpful feature in cold
climates.
Condensation Resistance of Windows: Measurements
The NFRC (National Fenestration Council) in discussing solar heat gain at windows, describes the Condensation Resistance of Windows (CR) as follows:
Condensation Resistance (CR) measures how well a
product resists the formation of condensation. CR is
expressed as a number between 1 and 100. The higher the
number, the better a product is able to resist condensation.
CR is an optional rating, and manufacturers can choose not
to include it on their NFRC labels.
Also see CONDENSATION or SWEATING PIPES, TANKS and DEW POINT TABLE - CONDENSATION POINT GUIDE as well as HUMIDITY LEVEL TARGET and see
SKYLIGHT LEAK DIAGNOSIS & REPAIR
Diagnose & Repair Skylight Leaks
Rooftop Skylight Leaks
Water Testing Skylights
Repairing Skylight Leaks
Avoiding or Preventing Skylight Leaks
Industry Associations for Windows & Doors
American Architectural Manufacturers Association
(AAMA)
www.aamanet.org
Efficient Windows Collaborative
www.efficientwindows.org
National Fenestration Rating Council (NFRC)
www.nfrc.org
Sustainable by Design
www.susdesign.com
Shareware calculators for sun angles, solar heat gain,
and shading
Window and Door Manufacturers Association
(WDMA)
www.wdma.com
-- Adapted and paraphrased, edited, and supplemented, with permission from Best Practices Guide to Residential Construction.
Frequently Asked Questions (FAQs)
...
Ask a Question or Search InspectApedia
Use the search box below to ask a question or to search the InspectApedia.com website.
Ask a Question or Enter Search Terms in the InspectApedia search box just below.
Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
- Basic Housing Inspection, US DHEW, S 352.75 U48, p.144, out of print, but is available in most state libraries; New York State version, ca 1955, source of our window parts and window repair sketches.
- 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.
- "Solar Heat Gain & Windows, the facts about", NFRC, National Fenestration Rating Council, January 2005, NFRC website: www.nfrc.org retrieved 12/4/2010, original source: http://www.nfrc.org/documents/SolarHeatGain.pdf.
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.
|
- 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
- The Journal of Light Construction has generously given reprint permission to InspectAPedia.com for adaptations, quotations, or reproductions used at this website. All rights and contents of the JLC material are ©Journal of Light Construction and may not be reproduced in any form.
- ...
