Depth of dual-pane interior or exterior storms

I called a window guy to get a quote on something that will leak less heat than the old single-pane windows that we have. I want dual pane, low-e, argon filled Energy Star windows.
One of my ideas, on the non-operable (i.e. windows that don't open) windows was to have interior storm units. It struck me that I have plenty of space to put windows there, but he said that no, 2 inches is not enough. All of the dual pane units made in Canada, he said, are the same depth. I don't remember the exact figure he gave, but it was more than 3 inches. I have that much space on the sill, but only a touch more than 2 inches between the posts.
I'm wondering, is this provision of big frames from necessity (you don't want the units leaking air in, because then the argon leaves and you lose some of your insulation / noise reduction value, and risk condensation), or from habit? Yes, I can see that it could be tricky to devise a framing system which would keep the seal intact while the unit was being installed (torque applied to the unit) or if it suffered some trauma (like a ball hitting the glass, but with insufficient force to actually break the glass), against temperature gradients, or against differences in tension during installation.
He said there would be no problem fitting a *single pane* interior or exterior storm in the space available. If I want dual pane, low-e, argon filled, he says it's likely that I have to replace the wooden sash units with vinyl.
So my subsidiary question is: is there any sense in buying "naked" dual-pane units and making wood frames (similar to picture frames) for them myself? I repeat that I'm asking this only about non-operable windows. Brief idea: drill hole at bottom of existing sash (to allow air flow against condensation) affix good quality weatherstripping on existing windows, place new unit in frame against weatherstripping, fix in position (low compression), and seal any leaks.
What do you think? Likely to work, or likely to fail?
--
Jonathan Berry


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your windows are the view to the great outdoors. depending on where you live the building met a design similar to one that that required perhaps ten percent of the size of the floorspace in a room or more to be windows of which half of that window had to open for ventilation and in case of fire. screw up the windows and you screw up your own view with frost, fog, moisture, dirt, and storm window hassles. it will be life as viewed thru a clear vinyl garbage bag. you could be viewing your best view through old thin rippled antique windows that are dirt and acid rain etched and begging to be replaced. start with the homemade idea on one window in the room where only you will will see it daily. try it for a year. remember you and the future owner want the sparkling new clear insulated views of moon and stars and space station above and the garden and swimming pool below.
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Im sure the 3" is for a rigid frame so they dont flex and have half a chance of making it 5 years before leaking and being ruined. Look into acrylic storms, removable, I dont know R value bet im sure its more than single pane
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replacement windows. Why have custom made "naked" glass panels made and then try to fit them and worry about leaks? You can get a fixed pane replacement unit (Installs just like a Double hung unit) and be done with it for probably less money.
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calhoun wrote:

Thanks for the question, it made me examine things more closely. Replacement windows are generally vinyl. I really dislike vinyl.

With these window dimensions, any upgrade is "custom"

This house was built around 1930. As far as I can tell, it still has its original windows (75 years). The windows are not leaky (of air). They are in pretty good shape. They are single-pane and thus toss out too much heat. Contrast that with the lifetime of vinyl dual-pane replacement windows. Somebody correct me if I'm wrong, but we're looking at: 2 years -- cra* material and installation 5 years -- deficiency in material or installation 10 years -- excellent quality in sunny window 20 years -- excellent quality in shady window.

First estimate is that the naked dual-panes, not installed, would cost about half what the framed replacement units would, installed. I think that's a pretty good deal for the installation, I'm not complaining. But I have no evidence that a fixed pane replacement would be less money.
Thanks for all the comments.
--
Jonathan Berry


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Some replacement windows are vinyl , maybe the cheaper ones, I have wood Pella, aluminum clad exterior 20 yr glass warranty. There are fiberglass , composite and others. Look at quality like Anderson, Marvin, Pella. Whole windows are much better as air infiltration is overlooked on old windows.
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