Thermopane-in-My-Butt Windows

Home Inspector with Charles Buell Inspections Inc.

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

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Myrl Jeffcoat
GreatWest Realty - Sacramento, CA
Greater Sacramento Real Estate Agent

I installed thermopanes in my home about 16 years ago, and already, 3 of the panes have failed.  I fear one will be expensive to replace, because it is one of several matched panes that make up my dining bay.

Apr 11, 2017 03:40 PM #1
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Excellent rant, Charlie.  And true.

Also, with the thermal camera one can show that when the gas disappears the energy efficiency of the window is not decreased...

Apr 11, 2017 03:42 PM #2
Dick Greenberg
New Paradigm Partners LLC - Fort Collins, CO
Northern Colorado Residential Real Estate

Hi Charles - I have to agree with you. Around here, failed seals are probably a top 5 inspection complaint item in houses over 10 years old - I showed a nice home last fall that had over 20 bad seals. I don't know what the answer is, but it wouldn't take much to do better, long-term.

Apr 11, 2017 04:00 PM #3
Kathy Streib
Room Service Home Staging - Delray Beach, FL
Home Stager - Palm Beach County,FL -561-914-6224

Charles- we had them on our sliders in our last house here and yes, they failed, looked awful and were not inexpensive to replace. 

Apr 11, 2017 06:43 PM #4
Kat Palmiotti
406-270-3667 (MT), 914-419-0270 (NY), Broker in NY with Grand Lux Realty and in MT with (coming soon!) - Kalispell, MT
The House Kat

We viewed a home a few days ago and almost all of the seals on the windows had failed. They were all cloudy. Growing up we had to put the storm windows up every winter. That worked just fine.

Apr 12, 2017 03:38 AM #5
Sandy Padula and Norm Padula, JD, GRI
HomeSmart Realty West & Geneva Financial, Llc. - Carlsbad, CA
Presence, Persistence & Perseverance

I feel your panes, er a pain Charles Buell . When I was a homebuilder, we standardized with Pella Windows and never had a call-back. A great product!

Apr 12, 2017 05:57 AM #6
Fred Hernden, CMI
Superior Home Inspections - Greater Albuquerque Area - Albuquerque, NM
Albuquerque area Master Inspector

When people ask me about upgrading their windows I tell them to find out how much it will cost, how much will they save in their energy bills, and how long will it take to recover their investment. Or, will they even own the home when that time arrives!

Apr 12, 2017 07:51 AM #7

I have a 1955 MCM with massive single pane windows. Total heating AND cooling cost annually is about 1200, and it could be a lot less if I didn't like my house toasty! Estimates to replace the single with double glazed windows are in the 30,000 range... and might reduce my heating bills by a few hundred dollars a year. Even if it cut it by 25%, an impossible task, it would save me 300 a year...and take 100 years to break even.

I'm always amazed when people ask me when I'm going to 'upgrade' my windows.

Apr 17, 2017 03:41 PM #8
Paul S. Henderson, REALTOR®, CRS
RE/MAX Northwest. - Tacoma, WA
Tacoma Washington Agent/Broker & Market Authority!

 One happy seller told us after our inspection that the windows were meant to be like that because it was like an art form Charles Buell 

Apr 20, 2017 10:20 AM #9
Debb Janes EcoBroker and Bernie Stea JD
ViewHomes of Clark County - Nature As Neighbors - Camas, WA
REALTORS® in Clark County, WA

Well isn't this timely?  We have a new listing and I tried to tell the seller the seal was broken on one their big picture windows.  They don't believe it and are sure it just needs to be cleaned. I guess the inspection will tell the real story - when we get to that point. 

Apr 29, 2017 01:53 PM #10
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Charles Buell

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