Well let's just say that I'm not a normal person.
For one thing, I don't really like replacement windows. In my mind, they are just not right. In order to save effort, the replacement windows sits inside the old frame. This means that the new window glass area is smaller than the old window glass area. It also means that the pockets containing the window weights don't get dealt with and any pre-existing issues with trim leakage are not fixed. The replacement windows can also be very expensive. I got a quote that amounted to $1500 per window installed.
So I decided to take a crack at installing some "new" (not replacement) windows myself. I put two double hung Andersen windows in the Master bedroom and one in the master bathroom. The results are mixed. The new windows look great and operate great. They are a big step forward compared to the old windows and storms. But the insulating quality is just not that impressive. The windows are roughly R3 which is nowhere near as good as the walls and glass still has some condensation issues as a result. Also, I spent about $600 per window between the window itself and the supplies. It should be said that there are less expensive windows and I purchased the windows that I wanted rather than shopped on price.
Seeking an alternative, I found something called "innerglass" (http://www.stormwindows.com/). This company's main focus is to supply "storm windows" for historic homes. Storm windows are typically not allowed in historic homes because it changes the appearance too much. Innerglass storms are installed on the inside of the window and use a compression seal to seal to the window frame. The innerglass storms are all but invisible, seriously.
But I had a different idea of how to use these. I already have outer storm windows and wondered if I could improve my windows by adding an additional inner storm window. I purchased two of them (about $210 each) a couple of years ago and I think they are great. They definitely improve the old windows, but they are even better than the new windows because there is effectively triple glazing.
On the down side, you don't really have an openable window with the innerglass installed. This is not a problem in the winter, but in the summer I remove them so I can open the window. Also, there is probably a fire safety compliance issue because bedroom windows have to be a means of egress. While I do have these in our guest bedroom, it is almost never used so I don't worry about the compliance issue.
In addition to some new Andersen windows and two innerglass windows, there are a number of old windows in the house. My home is really an experimental playground for windows. One cold day (today actually) I took some data. First I put a Post-it note on the glass of each window of the house (somewhere in the middle) and let it reach temperature. Then I used an IR thermometer to measure the temperature of the Post-it note. The reason for the Post-it note is to overcome any emissivity issues that I might have taking IR measurements on glass.
The dramatic results are shown below. (larger numbers are better)
| 63 | °F | double hung: single pane/storm/innerglass |
| 62 | °F | single pane/double pane |
| 61 | °F | New Andersen double pane |
| 55 | °F | Fixed: single pane/storm |
| 50 | °F | double hung: single pane/storm |
At 63°F the best results came from the old single pane windows with storms that I added innerglass to. This effective triple glassing is actually better insulation than getting new double pane windows. It is also much less expensive. The downside is that the windows are not really openable and the innerglass panels must be removed and reinstalled on a seasonal basis.
At 62°F is one small sidelite window on the front door where I have added a custom double pane storm to a single pane window. see post here http://doublepane.blogspot.com/2013/03/storm-window-for-sidelite.html Again, triple glassing is effective.
At 61°F is the New Andersen windows. We should give them their due. They are certainly a big step up from the old windows. But they are still a far cry from the 70°F surface temperature of the wall near the window. In other words, the Andersen window suck, just not as bad as my old windows.
At 55°F is the two large fixed pane picture windows with fixed storms that I have at the front and back of the house. This is pretty bad because not only are the windows poorly insulating, they are also very large.
At 50°F is one of my old double hung single pane windows with storm window. So it is clear that the Andersen windows are a big improvement, just not as big as I would like them to be. I have four of these old double hung windows left in my house, one in the guest bathroom and three in my son's room. I really need to do something. I wonder if Andersen makes any triple glazed products.
Shades
One final test was to repeat the temperature measurements after pulling the shades down. This was only possible on the Andersen windows which have thin roller shades and on the large picture windows which have double honeycomb shades which are sold as highly insulating.
The roller shades decreased the surface temperature by 2°F indicating they provided only a small insulating value.
The double honeycomb shades, on the other hand, decreased the glass temperature by a full 8°F showing their great insulating value. However, it should be noted that this exacerbates condensation issues on the glass because the glass temperature is even colder.
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