TIA, There are various versions of LowE glass available and there are various levels of visible transmittance in those various versions. You can also get a tinted LowE which does have the low VT that you mentioned or even lower is quite possible. Depending partially on the type of LowE coating used, very few people will notice LowE in a window or any difference in the natural light in a room when using a LowE coating. Some people say that they don't like LowE because of color issues or light issues, but that is rare and it is often people who have predetermined that they won't like it that often don't like it. Of course there are certainly people who do see the difference, just as there are people who can hear things that others can't. We are not all the same after all. The NFRC calculation is a "whole window" calculation that includes the sash and frame components as well as the glass. So a window with a wider area sash and frame will have a lower VT than a window with a narrower profile even if both use the same glass. Of course there are also calculations for glass alone as well. One pane of clear glass, 1/8" thick, has a VT of about .93 - with some dependence on what company - and even what plant - made the glass. But that should be pretty close. Add a second lite and the VT drops to about .86. Add a third lite and it drops down to about .80. So two lites of glass with a LowE coating will top out at about .73 or so...maybe even a little better (and btw, I am doing these calculations from memory - I believe that they are correct, but I am going to verify them later by looking at actual graphs of the measured and calculated VT performance). Ultimately, will you notice the difference between a LowE window with a higher VT than a clear glass panel? Truly, only you can decide whether you can or not...you will notice a difference with a tinted or high solar control LowE however. A clear glass IGU or dual pane window will make you more comfortable than you will be with a single pane window. But it won't make you as comfortable as a dual pane with a LowE coating. The LowE coating will make a substantial difference in comfort level in the room in both winter and summer months...even in a moderate climate like yours. Payback? That is a very good question and one that is misused and abused all the time. You MAY (note may) save enough to pay for the windows in a number of years. Sales folks who tell you that replacement windows are ultimately "free" because of saving energy dollars will pay for them in 3 or 5 or 7 years are either (a) misinformed, (b) misinformed and exaggerating claims, or (c) less than 100% honest. Don't plan on buying new windows with the idea that they will save you enough money to pay off the mortgage and the kids' college fund and pay for that trip to Europe...won't happen. Don't buy them thinking that you will quickly recoup your money based on the savings dollars...again, won't happen. Do buy them with the idea that you are going to be more comfortable, you will save some money in energy costs, and if LOTS of folks save those few dollars a month it adds a number of tangible and intangible benefits for all of us. How many dollars a month will you save? Hard to say really...depends on a great many factors including how tight is your home? what kind of heating system do you use and what are the local rates? your own lifestyle can affect the amount of savings...but, don't plan on it being huge. A 20 to 25 year payback might be realistic or it could be a little longer or a little shorter...again, too many variables to make a really accurate prediction. Don't use payback as a deciding factor. Finally, there have been MANY studies, formal and informal, on the effect of LowE on plant growth. The results every time is that a non-tinted LowE has no detrimental effect on plant growth and can actually enhance growth in plants that are UV sensitive or that like semi-shade. LowE blocks light in the UV and IR spectrums. It has relatively little effect on the visible spectrum - which happens to be the light spectrum that plants need to grow and thrive. TIA, good questions! I hope that my answers made sense to you and feel free to ask more if I was unclear or if you think of more to ask...enjoy your day.

Thanks for the responses to my post. The windows are casement windows. I just opened one of them and it looks like they could probably unscrew the window from the support bracket and replace it. I haven't talked to Champion yet because I want to be more knowledgeable before I do. There were so many problems with the quality of the windows and the install that I don't want to have any doubts about the accuracy of what they tell me, so I'm still hoping someone can tell me how the seals in a double pane window can be tested. Quite honestly with the history of this install I'm worried about whether or not I can trust any replacement they make for me. The windows do have the Good Housekeeping Seal of Approval and Champion is a member of the Better Business Bureau, so I may end up contacting both of those agencies as well.

3bean3, Just now our 100 year old house is without its nasty white proud-sitting triple track aluminum storms for the first time since we moved in 11 years ago. It is lovely to see the original 6x6 and 6x9 windows unobstructed, until they are repainted and new storms are installed, design yet to be determined. But suddenly we are very aware of street noises, while before our house was very quiet. Also, we have one less layer of security in our northeastern urban neighborhood. I'll be very glad when we have settled on a design for storm windows and they are installed. In our neighborhood, a number of house-proud neighbors have chosen those wooden storms with fixed upper panels and interchangeable storm/screens below. I am torn about losing the ability to open window sashes at the top to exhaust hot air near the ceiling. Have you thought about installing nice full-length screens on the outside, and magnetic interior storms? Some on the Home Forum say that this will make your original windows deteriorate faster, since they will remain exposed to the elements. Others say that condensation is actually a greater threat to your windows and that interior storms do a better job of protecting them from condensation. I'd be interested in hearing what Oberon, WoW, Trapper, brickeyee, xoldtimecarpenter and sombreuil have to say to that. Apparently many historic preservation districts require this solution. But somewhere in my research I remember someone -- Mr Yapp? -- pointing out that our old houses never were meant to be without storm windows -- people just rotated full-length storm and screen panels twice a year. And my friends who live in a meticulously restored 1740s farmhouse in Connecticut do just that -- they are the most historically correct homeowners that I know. This question makes a small bungalow seem mighty appealing about now: possibly the best solution! Your thread has attracted the great wizards of the Home Forum: their guidance is invaluable -- I just wanted to add a couple of less technical points that I think you might want to consider. Lynn

good morning Jan, Laminated glass is not an energy product. It is very expensive and would add nothing to the overall energy performance of your windows. You are obviously unhappy over losing the original windows; have you considered restoring them rather than replacement? Although to be honest windows made in the late 40's tended to be a good bit less quality than those made a few decades earlier - with exceptions of course. I can appreciate why you like the simplicity of the single pane wood window, just as I appreciate (and often agree with) the desire of many folks to restore rather than to replace their existing windows. But, despite comments from the restoration industry that restored windows with storms are every bit as energy efficient as the newer windows with all the "bells and whistles", that is simply not the case. Ultimately, restoring older single-pane windows or installing single pane windows is an indulgence that has to be taken as such. My impression from your posts makes me think that you see it that way as well. And while I am not suggesting that certain "indulgences" are not acceptable - again, I often agree with restoring older windows - we have to understand potential the trade-offs involved in doing so. Relatively few dual pane windows made today have aluminum spacer systems. The majority of dual pane windows use one form or another of "warm-edge" technology spacer systems. These warm edge spacers range from stainless steel through completely metal-free systems. All of the newer systems are much better than what was used in dual pane windows even 15-20 years ago. Differences between the best systems used today and those used 20 years ago are such that there simply is no comparison. Like most new products, there was a learning curve involved in developing dual pane window systems. While many folks do have concerns about longevity of dual pane systems - and very justified concerns in many cases - even the less-advanced systems in use (older and newer) generally have historical failure rates of less than 20% based on the glass system - which is where most people's concerns seem to focus. While the better, newer, systems often have failure rates in the tenth of a percent range (or better) and those failures that do occur with the better, newer, systems are almost always related to human error somewhere in the process. And while there is no question that a 20% failure rate in any product is totally and completely unacceptable, one would think that there is a 110% failure rate of dual glass windows based on what some people in the restoration world claim. Sometime last year (give or take) the California department of energy published a document that stated that replacing all of the single pane and less efficient dual pane windows in the state with state-of-the-art dual and triple pane windows would result in energy savings equivalent the energy output of two (or maybe three I forget) new power plants  and at a cost significantly less than the combined costs of building and operating those plants (over a 20 year period if I recall correctly). Thus my assertion that restoring windows is an indulgence  one that I often agree with  but still with the understanding that there is a trade-off involved versus replacement with an energy performance state-of-the-art replacement. Anyway, sorry so long  and I did tend to veer off track a bit  but ultimately making sure that whatever fills the hole in your wall is operating at its peak efficiency is going to benefit you. And, if you choose the replacement option donÂt forget the quality of the installation  that is so very important! Have a great weekend!