This is a rant that has been simmering for a few years.
However well intentioned, I think the whole notion of thermopane windows is misguided. When I started building houses in the mid 70’s the idea had really taken hold as people became interested in conserving energy and improving the comfort of their homes.
It was not long before the requirements for insulating glass became codified with different requirements varying with climate.
We are now more than 40 years past the time when I started building and most of the seals have failed on those windows. That is, except for the windows that were not sealed thermopane type. Many of the houses I built had Pella type windows with removable interior panels. Those windows are still performing exceptionally.
I do not belief it can ever be economically justified–over the life of the house–to install thermopane windows when you factor in the cost of replacing all that glass in less than 30 years. This becomes even truer if the windows are triple-pane or have funny gasses pumped into them or reflective coatings applied to them.
Some of the newer windows with the “Warm Edge Spacers” are known to fail in less than 15 years.
I think it is time to revisit the whole business of insulating glass windows and see if the use of removable panel type insulating glass–or even old fashioned storm type windows might have some merit–or at least be an option. Throwing money at the fruit so far off the ground may not have proved to be the wisest path–and is rotting by the time we get to it.
The amount of energy expended to create thermopane windows simply cannot be justified against how long they last. Well cared for windows should last indefinitely, whereas sealed unit, thermopane windows are a version of job security for the windows replacement industry.
I installed thermopane windows in my kitchen about 18 years ago, and this year two of the panes failed.
This is unacceptable in my opinion. The labor and materials to replace these units will easily cost more money and consume more energy than any imagined savings accrued over the 18 years. If the windows had been a removable glass panel type windows, they would have continued to keep on saving energy, eventually even paying for themselves over the life of the home—probably sooner.
I would like feedback from anyone that can make a case for sealed unit, thermopane windows.
Charles Buell, Real Estate Inspections in Seattle
Charles – How dare you introduce logic into the building industry! 😉 You are fighting too many battles with this: too many centuries of Western European tradition of number of street-facing windows = degree of wealth; too many architects thinking that everyone should live in total glass-wall houses; too many home buyers wanting both cheap and convenient building supplies (i.e., no outdoor maintenance). I even tried to make the case on the Passive House forums about having NO windows to lower the construction costs and increase number of builds. A good HD camera and 60″ LED TV would be less expensive, have no shell perforations to leak, and enable the shell to have a better overall R-value. The response was that everyone NEEDED to be able to throw open their windows to provide fresh air (despite having very expensive mechanical ventilation, most people never opening them anyway, and especially at night or when absent due to security concerns) and NEEDED to have sunlight coming in (even if it overheated rooms with East/South/West exposures and little daylight through Northern exposures). Despite what is bandied about in the advanced building trades/forums, lots of “Wild West snake oil” is being sold without regard to true building lifetime (get someone to really give you an honest number on that) costs and true comfort reviews that include all 4 seasons (including actual, measured IAQ).
To the specific question at hand, we used Anderson vacuum glass panel windows (NLA)in some early remodeling and they seem to be holding up quite nicely even with periodic exterior maintenance. We had 16 Gorell vinyl replacement windows (NLA) installed vs 1930 wood double-hung units (even though I installed triple-track storms) only for ease of maintenance (painting/cleaning) and operation. We have tried to take very good care of them and they have been good so far. But you are right, the general lifetime is around what the warranty provides. And heaven help you if you have them installed by someone other than the manufacturer.
Thanks David, I am prone to tilting at windmills having been involved in all of this since the early 70’s before it was cool to be green. Another one of my pet peeves is the silly notion that great savings only come with great cost. Gadgets rule.
The Pellas units I was talking about were in the Lake Ontario/Syracuse/Oswego area of NY State—so not exactly above 40 degrees in the winter. Do you keep the vents clear at the exterior? There is an insect that likes to build nests in them so you do need to maintain them open. Never had a fogged window in the house I lived in with these Pella windows.
When my X in Ontario tried to “fix” the caulking around the thermopane sliding glass doors!!!! He hit the seal and it popped, & shattered!!!!
Well, he found out it was Safety Glass for sure 🙂
And another photo.
I couldn’t agree with you more. I’ve been a professional millworker for 20 years; now faced with the prospect of building new windows for my 1800’s Greek Revival I find myself unwilling to put any IGU’s due to the failure rate, not to mention they are just plain ugly.
There is a company making windows that look good using IGU’s (www.heirloomwindows.com) but this doesn’t address the fact that you’ll be stuck with replacing them in 20 years or less. Fortunately you can get single pane windows from that source as well. I’m impressed with the thoughtfulness and thoroughness of their approach.
VIG window glazing which has been sealed using welded glass (just like the original Thermopane glazing of the ’50’s) might be a good answer, but unfortunately the old technology has been lost and the new is not ready yet for the likes of us. Last I checked, anyway. If you know otherwise, let me know!
I have a question for you, which is: could you please provide some details for the removable panel system on those Pella windows, and how well does it work? How does it look? I’ve never seen it and I can’t seem to find a diagram on the Pella website (probably there’s a reason for this). Does condensation develop between the glass layers? Is the panel used with a divided lite window, and if so, does it cover the entire glazing area including the muntins or is it sized for each individual pane?
Thanks
The Pella removable panels work GREAT but they no longer meet energy code requirements (absurd in my opinion). You can get them from Pella in a triple pane version but that does not help much in my opinion. I visited a house last year I built 34 years ago and they looked great. You would not find them to your liking in true divided light however—the “look” of multiple panes would be done between the glass. I think with windows we are looking for perfection of energy savings just is not possible and we have to settle for what is good enough. The Pella removable panels IMHO were good enough and more energy efficient than any regular thermo-pane type window when you start to factor replacement of failed seals.
Hi Charles,
Seattle, or your general area, must not get below 40 degrees. I’ve attached a photo of 1 out of the 23 windows I believe you are describing as your Pella units. All units produce condensate, and guess what happens when it gets below freezing? Yes, your condensate is now ice. If it gets below zero degrees the entire (outer pane) is entirely covered with ice! It makes no difference if it is a S,E,W or north facing unit. But if the sun comes out, as you might guess, the ice then melts and runs down to the bottom of the sash. There is NO way this designed unit should have been sold in climates where it consistently goes/stays below 40 degrees. And to top it off Pella will do nothing about it! Except sell you new windows.
The thermalpane units installed at the same time about 17 years now, are working just fine.