Insulating Glass Failures
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johnleeke
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Joined: 20 Aug 2004
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Location: Portland, Maine, USA

PostPosted: Wed Jun 14, 2006 10:02 am    Post subject: Insulating Glass Failures Reply with quote

Here's some more "ammo" for the good battle against the window replacement pirates.

> Has anyone converted their single pane windows to
> thermopane? How did you do it?

"Thermopane(r)" is a particular product developed in the 1950s that is is an envelop of glass that has the glass itself wrapping around the edges as a continuation of the flat glass. The word "thermopane" is now often used to describe a fundamentally different type of product called "insulating glass." True Thermopane(r) is not plagued with edge sealant failures as are the more current "insulating glass" panes.

I think you probably are talking about "insulating glass," that is two separate sheets of glass sealed at the edges with metal strips and flexible sealants. I have seen insulating glass installed in thick sash by removing the original glass, routing out the glazing rabbet deeper and installing the insulating glass panel. Two out of three projects where I was involved had fogging failures and have since replaced most of the panels. On one project they have already begun a second round of replacement and it is questionable whether their wood sash will hold up to the damage that would be caused by a third round. To say the least this building owner is wishing he never had thrown out his nice 1/4" plate glass panes.

This type of double pane insulating glass is well-known within the glass/window industry (although you will not hear about this through their marketing) as having a life of about 10 to 20 years, when it sometimes fails by loosing the seal and becoming opaque by "fogging" on the interior surfaces. First generation insulating glass products sometimes failed within 5 to 12 years. Now, second generation products are promoted as having solved all those early problems, but even some of these are now failing after 12 to 15 years. (do not be confused by 20 year or life-time warrantees, which are just marteting techniques and have little to do with the length of service life of the product) If you do not need to see through the window fogging might not be considered a failure, but most windows that fail this way are replaced. If one considers their relatively high cost and short life the payback when compare to other window treatments (such as single-pane primary sash and single-pane storms) the energy dollar savings payback is rather high, and almost always two or three times longer that its expected life. (so you end up replacing it before its initial cost is recovered) The glass/window industry does a good job of hiding these facts from their prospective customers. Lawsuits have been decided in favor of commercial and institutional building owners who were duped by the insulating glass manufacturers and their marketers. Most residential failures are at a smaller scale and are simply accepted by the homeowners and even higher cost replacements are installed.

Learn more at:

For insulating glass failures you want to read Dez Farnady's (outspoken glass industry insider) "Farnady Files in USGlass magazine, such as:

http://www.usglassmag.com/backissues/0211/Farnady.html
(this link does not work, the article has been removed from the USGlass website, but you can find it here:
http://web.archive.org/web/20041020033136/http://www.usglassmag.com/backissues/0211/Farnady.html

His best piece on insulating glass failure was in USGlass April 1995, which I have on paper, but it does not appear to be on the USGlass website.

...and:

http://www.usglassmag.com/backissues/0211/Farnady.html
(also removed from the USGlass website. Do you get the idea the glass industry is keeping secrets from us? With a little detective work I found it on the internet archives:)
http://web.archive.org/web/20041020033136/http://www.usglassmag.com/backissues/0211/Farnady.html

where good ol' Dez talks about his own house, which appears to be a vertiable museum of insulating glass failure. (much like my own rotten wood collection here in Portland!)

For an engineered energy analysis summary involving insulating glass in a residential situation see:

http://www.historichomeworks.com/hhw/education/WindowsHandouts/WindowEnergyAnalysis.pdf

(I only have permission to hand this out at my workshops, so please don't pass it along to anyone.)


John
by hammer and hand great works do stand
www.HistoricHomeWorks.com

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Harold Pomeroy



Joined: 26 Apr 2006
Posts: 25
Location: Chesham Station, NH

PostPosted: Wed Jun 14, 2006 8:43 pm    Post subject: Reply with quote

By hammer and hand we turn insulating glass back into sand.

Harold
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johnleeke
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Joined: 20 Aug 2004
Posts: 2968
Location: Portland, Maine, USA

PostPosted: Wed Jun 14, 2006 9:21 pm    Post subject: Reply with quote

HA!
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