Condensation at a basement window (C) Daniel Friedman Window Condensation: Cause, Cure, Prevention, Resistance Ratings
     

  • CONDENSATION on WINDOWS, SKYLIGHTS - CONTENTS: Window condensation causes & effects on the building. How to cure or prevent condensation on windows and skylights. Condensation-resistance ratings for window glazing. Outdoor Temperatures at which condensation occurs on windows at 50% Relatiive Humidity indoors
  • POST a QUESTION or READ FAQs about condensation on windows: troubleshooting, cure, prevention of window condensation & moisture
  • REFERENCES

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 2015 InspectApedia.com, All Rights Reserved.

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.

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.

(C) J Wiley, S Bliss

(Also see CONDENSATION or SWEATING PIPES, TANKS and DEW POINT TABLE - CONDENSATION POINT GUIDE as well as HUMIDITY LEVEL TARGET.)

[Click to enlarge any image, photo, or table]

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

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.

More Reading

Green link shows where you are in this article series.

...




Frequently Asked Questions (FAQs)

Click to Show or Hide FAQs

Ask a Question or Search InspectApedia

Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

HTML Comment Box is loading comments...

Technical Reviewers & References

Publisher's Google+ Page by Daniel Friedman

Click to Show or Hide Citations & References