Are Triple-pane really worth the extra $$?
Last Post 10 May 2009 11:27 PM by ecobuilder. 29 Replies.
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hoheUser is Offline
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06 Jan 2009 05:23 AM
I am replacing all of the windows in a 3000 sq ft home as part of a total gut/rehab. It's a typical New England cape with windows primarily on the south side, but a fair amount on the north (front) and east sides as well. I am insulating with spray foam and generally want to make the tightest, most efficient envelope possible. Being in the northeast, the canadian fiberglass triple-pane/krypton windows seem like the right choice with U-values around .20. I also checked out the Marvin Integrity windows, which are double-pane/argon with a U-.30. The canadian windows are about $7000 more. My question is, are they worth it? I recently plugged our numbers into RESFEN, including southern exposure and SHGCs, and was surprised to learn that the 3-panes save me only about $150/year. Even at $200/year, that's a 35-year payback. That's a pretty long time. Now the 3-panes don't seem like such a good choice. Am I missing something? Thanks!


Stephen TUser is Offline
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06 Jan 2009 10:24 AM
I suspect your savings numbers are reasonably accurate - for current energy rates.... 

It might be even better to use a more detailed simulation tool like Energy 10 or HOT2000.  Either would get you an answer more specific to your house.  Although the results would be more accurate, the payback would likely still be long by most people's standards.

In new buildings it's relatively easy to go beyond conventional insulation levels and airtightness. There it makes sense to look at triple glazing, because otherwise the windows are such a large porportion of the heat loss.  If you put the whole package together; a highly insulated, air tight envelope with great windows, you won't need a conventional furnace.

In renovation work, we talk out of the other side of our mouths. We focus on condensation resistance and comfort.  Occasionally, a customer who is both technical and thrifty will triple glaze the north, but not the other orientations. Invariably, we'll hear back at some point that they wished they had gone triple everywhere -- for the difference in condensation.  

The other core argument for triple glazing in renovation work is the improved comfort.  Simply put the window is warmer, so it's got to be crunchy cold before you feel a draft off the glass. This is most noticeable on larger windows.

A final, more circuitous argument about overall quality.  Most Canadian Fglass windows are available with insulation in the frame. While good from a marketting point of view, there's a solid (but long winded) reason for it.  Fglass is strong enough that , unlike vinyl, multiple chambered frames are not needed.  For the most part, many uninsulated fglass profiles are hollow cavities. Thermally, this is somewhat similar to a warm edge double glazed thermopane - without the low e or argon.  As many know, even a warm edge double glazed thermopane can get condensation along its bottom edge in cold weather.  With uninsulated fglass frames, the condensation can appear near the bottom of the jambs or sash stiles.  So while it seems the triple glazed vs. double glazed decision is just that, there are other issues that creep in.....

Hope this helps.



Stephen Thwaites P.Eng.
Thermotech Fiberglass Fenestraion
Ottawa, Ontario
stonecavemanUser is Offline
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06 Jan 2009 10:47 AM
I just took out the last of the 50-year old windows in my house. Metal frame, single pane, leaky as heck.

New windows are stock, ~R3. I keep wondering if I should have gone for better windows, but I took the same cost approach and realized that the price escalates rapidly with performance.

Looking at the improvements in recent years, and the possible improvements down the line - one of the other threads links here:

http://www.metaefficient.com/windows

The possibility of vacuum windows,(http://homerenovationtrends.wordpress.com/2008/08/08/vacuum-insulated-windows/) etc. etc. I have a feeling that in 10-15 years, possibly even sooner, I'll be willing to change out the windows for something that has much better performance than anything I could buy today for any amount of money.

I do live in New Mexico so it's (usually) a little warmer and dryer than where you are - although it's only 12F here at the minute - so the immediate comfort factor may be more important to you


Jesse ThompsonUser is Offline
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06 Jan 2009 11:05 AM
Stephen got there first, but I would have said something similar.

In renovation, the "payback" might not be there strictly in energy bills or dollars saved, but you would gain comfort, interior warmth and less condensation on the interior. That might be worth extra to you, or it might not.

Lots of people do things to houses that don't have economic payback, but give pleasure and value (granite countertops, ornate tile, fine detailing, etc). You know the drill, a Corolla gets you where you need to go, but Mercedes still sells lots of cars.

It's worth getting in to see a house that has triple glazed windows at this time of year. If you haven't ever been in one, the physical difference of standing near a triple glazed window when it is 0 degrees out can be surprising. I know it was for me. You might try calling a window rep you are considering purchasing from to see if they have any installs nearby that might let you visit.

We have plenty of clients who stick with double glazed, double hung windows simply because of look and feel, even though a triple glazed casement performs technically far better in insulation and air infiltration. As always with houses, there are many things to consider...


Jesse Thompson
Kaplan Thompson Architects
http://www.kaplanthompson.com/
Portland, ME

Beautiful, Sustainable, Attainable
JConRUser is Offline
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06 Jan 2009 12:32 PM

Can you put the $7000 in perspective.  Is it double the cost of the Marvins? 50% more?  25%?

Thanks,  John


hoheUser is Offline
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06 Jan 2009 12:52 PM
It's about $23K vs. $30K. Thanks to all of you for your input. It is difficult to quantify "comfort". I'm living in a house now with Anderson 400s. We've had some very cold weather and I can't say that the windows feel noticeably cold. However, I've never experienced living in a house with triple-panes. Aesthetics also play into the decision. The dual-panes have a painted wood interior. The tri-panes are fiberglass on the inside -- a bit more "plastic-y" in my opinion and not as nice looking.


stonecavemanUser is Offline
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06 Jan 2009 12:52 PM
So the take home point seems to be that from better windows may not have an economic return but, depending on the climate probably have a comfort/quality of life return.

Your points are well taken, and I'd be extremely unhappy if I bought a high end home with all the interior decor you describe and then find that the windows are sub-par. Unfortunately, I suspect that might happen quite often if the buyer doesn't look a the quality of the building envelope before the counter tops.

I'm in the middle of a remodel/addition (4" foam on the exiting first storey and a SIP second storey addition) and I still think I'll go with double pane, with the anticipation of replacements in the not too distant future when the quality of the windows catches up with the quality of the walls. BUT that's a personal choice and just because I'm willing to tinker. If I was going for the 50 year low maintenance, I think I'd go with the best windows I possibly could - even if that meant sacrificing the granite counter tops.


AltonUser is Offline
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06 Jan 2009 01:00 PM


What are your thoughts about using insulated glass covered by storm windows?  Are storm windows as efficient as triple pane glass?  Will storm windows prevent condensation on the glass or sash?  What about cost differential between triple and storm windows?



Residential Designer & Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu, 334 826-3979
JinMTVTUser is Offline
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05 Feb 2009 06:59 PM
i was quoted at less than 10% increase in price for high perf double VS high perf. triple by fibertec
10% would result in 2500$ more in ur case, not 7000$
i had 45 windows though, but the % should be in around the same


jojoUser is Offline
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05 Feb 2009 10:03 PM


hoheUser is Offline
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06 Feb 2009 07:36 AM
gen,

Thanks (I think) for posting that link. Now I won't rest easy until the windows are installed and working well. I will follow up here with our experience with Fibertec.

JinMTVT -- the $7K difference was Fibertec triple vs. Marvin Integrity.


MNSideUser is Offline
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06 Feb 2009 12:11 PM
Greetings, one thing to consider is the added weight of the window with triple pane glass.  A large double hung window can be difficult to raise up for an older person.  I have replaced fairly new windows (triple glazed} that the female home owner and her retired husband could no longer raise.  Also on a casement window the added weight tends to wear out the crank out mechanism  much sooner. I live and work in central Minnesota and I sell more double glaze windows with a premium sealing system than the triple glaze.  One mnfg.  Ener Pro I believe has discontinued their triple glazed  casement window.


aardvarcusUser is Offline
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06 Feb 2009 12:24 PM
You can get windows with spring assists, my fathers old Pella double panes are that way. On one of the windows, the spring broke and you can tell a world of difference compared to the others.


stonecavemanUser is Offline
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06 Feb 2009 01:57 PM
Whatever happened to counterweights? Man you couldn't shift those old leaky wooden windows once the rope broke on the weight (even on one side). Of course, there was no hope of fixing the window because the screws that you needed to remove to get access to the cavities were already buried under enough coats of paint that you'd leave a huge divot in the wall if you ever tried to move them.

I do miss the old steam radiators, they had style and character. They'd sing to you and leak on the floor. And they were probably the only things that had enough BTU output to heat a place that leaky!


Dana1User is Offline
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06 Feb 2009 02:27 PM
I'm not a very experienced RESFEN 5 user, but have you properly adjusted the "Solar gain reduction" for the different aspects? In heating dominated climates like NH your net operational costs may go UP if the south-side windows go triple-pane vs. double. Your heat gain is more net-positive with double-pane than with triple, and the net AC load increase may be low,( or can be mitigated with shading.)

It's not uncommon to spec different window types depending on which side of the house it is. Since the bulk of your windows are S facing, you may want to look at that very closely before going triple-pane on that side.


mallisonUser is Offline
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08 Feb 2009 10:19 PM
I have Marvin Integrity in my 10yr old double 2x4 cellulose insulated, geothermal house in CT. Looking to build a smaller similar dwelling with various energy upgrades. I absolutely would move up from Integrity--for the condensation and attendant painting maintenance alone. I might go to some of the HM glazed windows, but at this point have no idea how expensive they will be. The Thermotech for about a 25% premium seems well worth it to me. Glazing is the weak link in a super insulated, no infiltration wall unless you want to live with portholes.


hoheUser is Offline
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09 Feb 2009 03:46 PM
Dana1 - The triple panes on the south side are tuned for high heat gain. That is something that the Integrity windows don't offer. However, I believe with the new Energy Star requirement that take effect in 2013, they will need to offer different glazing for heating dominated vs. cooling dominated climates if they want to keep their Energy Star status for the northern region.

mallison - Sounds like condensation was an issue for you with the Marvins? Your experience is exactly why we ended up choosing the triple panes. If we're spending the $$ to spray foam the entire house, then we didn't want to skimp on the windows! Did you have any other issues with the Integrity windows?

I checked into the ThermaProof HM windows (made by Alpen Glass in Colorado). Interesting technology. They were a little bit too new for my comfort level, but the pricing was comparable to true 3-pane windows.


SoCalScottUser is Offline
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01 Mar 2009 10:13 PM
FYI.....while the Thermaproof, now "Serious Windows" brand is relatively new, they purchased Alpen Glass that has been around for 25+ (?) years and are itaking the IG packages that they have been using in commercial applications for years and integrating them into residential "windows." Also, Serious Materials (manufacturer of Serious windows) has been manufacturing a high STC line of windows (Quiethome Windows) for at least 5 years now ay their own facility.
Translation: A "new" company doesn't necessarily mean new technology.


gregjUser is Offline
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01 Apr 2009 12:21 PM
Are there any triple pane windows out with a traditional wood interior rather than the plastic?


Jesse ThompsonUser is Offline
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06 Apr 2009 10:35 AM
Loewen, Weathershield, Marvin. All high-end brands. Make sure to dig into the U values and SHGC, they differ greatly across brands. Pella also sells a "triple", but it's a sealed double with a removable inner single glazed panel. Energy values nowhere near a true triple. Unilux and Optiwin are high end German windows available in the US. Non-traditional US style (tilt-turn) with extraordinary U values for a wood window.


Jesse Thompson
Kaplan Thompson Architects
http://www.kaplanthompson.com/
Portland, ME

Beautiful, Sustainable, Attainable
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