Replies

1. GBA Editor
   Martin Holladay|May 14, 2015 03:05pm|#1

   Ann,
   It would be helpful to know your climate zone, and whether this is a fixed or operable window.

   These days, there are many specifications to consider. If you care about energy efficiency, you need to learn about window glazing specifications -- especially U-factor and solar heat gain coefficient (SHGC). For more information, seeAll About Glazing Options.

2. 
   David Meiland|May 14, 2015 03:23pm|#2

   To quote glass replacement, I would need to know dimensions including overall thickness of IGU, specs if any for low e or gas fill, type of spacer bar desired, whether safety glazing is needed, etc., and of course the method of installation. If you were able to give them the approximate size and the type of window, a phone quote might be reasonable for someone who prices glass replacement all day, but I doubt they are assuming anything other than clear glass. The thickness of the panes themselves makes very little difference, although the 4mm might be a little better for your size.

3. 
   Ann Piece|May 14, 2015 03:31pm|#3

   Martin, Thank you. The article was very helpful. I realize, however, that I wasn't clear at all in my question. When I said "replace the window" i just meant replace the glass. I live in a cold climate with harsh winters, it's an operable window, south facing, gets lots of sun. Again, I'm replacing the glass because it has foggy streaks.
   So considering all the excellent points in the article, but considering that I'm just dealing with a glass manufacturer, what would you recommend that I specify to them?
   I'm beginning to think that by replacing the window glass but not the frame, I will get NONE of all the excellent features mentioned in the article- no gas, no glazing, no known U-Factor or SHGC, etc. Am I getting that right?

   That being said, the manufacturer of my windows is out of business, so I really don't want to buy and install a new window that doesn't match the rest of the house, and that will be a much larger expense than merely replacing glass.

4. GBA Editor
   Martin Holladay|May 14, 2015 03:39pm|#4

   Ann,
   If the unit is fogged up, I assume that you are talking about an IGU (insulated glazing unit) that is probably double-glazed. Right?

   You should certainly ask for an IGU with a low-e coating and argon gas fill, at a minimum, if you live in a cold climate. I would also ask the supplier what the U-factor and SHGC of the IGU would be.

5. 
   Ann Piece|May 14, 2015 04:11pm|#5

   Thank you Martin and David. You have both given me excellent material to work with in trying to buy new glass.
   Of all the things you both mentioned, is there any specification that I should be sure to match with the existing, 16 year old windows: e.g. thickness of glass, double-glazing or not , any other type of coating, spacer bar?
   Finally, is there anything in particular that is more likely to prevent this streaky fogging in the future?

   Thank you very much!

6. 
   David Meiland|May 14, 2015 08:11pm|#6

   Ideally, you identify the type of glass already installed in that window and use that as a starting point. If you're in a cold climate and the room with that window is not subject to summertime overheating because of a large glass area, you may want a high-SHGC low-e coating.

   Here's a guide to Cardinal Glasshttp://www.cardinalcorp.com/wp-content/uploads/pdf/Technical_Glass_Guide_Web.pdf.

   If you look at page 15, there is a chart that shows SHGC for various double- and triple- glazed insulated glass units. Their 180 coating is the highest-SHGC coating on the chart, and everything from there on down rejects more solar heat. Go to the next page and you can see the u-factors for IGUs, with and without argon gas fill.

   In a cold climate, without a summertime overheating problem, 180 is likely a good choice. If there is a lot of other glass nearby, you may need to just match what is there.

7. 
   David Meiland|May 14, 2015 08:18pm|#7

   To answer the question about preventing this again... not sure what you can do but buy from a good source. Glazing sealants seem to have improved a lot in recent years and I wouldn't worry too much about it.

8. 
   Steve Vigoren|May 14, 2015 08:38pm|#8

   I had five windows in my condo that were either cracked or foggy. I finally called a glass replacement outfit I found in town. They came over, measured the windows and a week or so later, came back and took the window out, then took it apart, put the new double pane glass in the existing wood, and put the window back in service. 100 dollars a window, I thought it was a deecent price. They were crankout casement windows.

9. 
   Ann Piece|May 14, 2015 10:13pm|#9

   优秀的答案。谢谢大家。