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Replacing Single Pane with Thermopanes

DesignBuild | Posted in Energy, Heating & Insulation on February 24, 2009 01:41am

Hi all — I have a large bay window in the living room of the house I recently purchased that I was considering replacing the single pane glass with thermopanes – should I expect a noticeable difference in the comfort of the room and is it worth the investment?

Details? The window bay is comprised of five large fixed panes with 5 transom windows below. The fixed panes were site-built, held in place on the interior side with a base molding laid flat, and there is plenty of depth to accommodate the extra thickness of the thermopane if I rip and re-install the molding. The transoms are also single pane but they are factory built, I don’t think they could be easily modified for the additional thickness so I was planning on leaving them as-is for now. Each of the upper windows measures 39″w x 66″h – so x5 we are talking over 75 total sq/ft of single pane glazing, and to top it off it is a north-facing window (I won’t even mention the un-insulated crawl space below).

I’m having a glazing company take a look at the job this week, just wanted to get some insights from good people around here. Thanks in advance for your thoughts.

Sean

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  1. Kungur | Feb 24, 2009 02:27am | #1

    I have started reglazing my Pella"double pane" widows with insulated panels. The Pella units have a removable interior panel. But I always had problems with them fogging up no matter what I did. So I replaced a number of them this past Fall and I must say I really notice a difference. Also I got LowE glass so I think it is a wisse move.

     

    1. Jay20 | Feb 24, 2009 04:46am | #5

      I have the same windows. I reweaterstriped them this past summer. Some went fast others I found problems I fixed and took some time. On average I am embarrassed to say I spent about an hour per window. Are you doing the work your self or having it done. If you are doing it your self I would be interested in the procedure you are following. Thanks Jay

      1. Kungur | Feb 24, 2009 02:52pm | #8

        I used a Multimaster with a scraper blade to remove the old glazing. After I cleaned all the old glazing compound I used glass tape then set the insulated panel inplace. I glued and bradded the newly milled stop, same angle as the old, in place. I used latex/silicon caulk under the new stop agaisnt the glass. I ran my ideas by the service guy from Pella and he said it sounded like a good idea. So basically I am making my Designer series into Proline.

        1. DesignBuild | Feb 24, 2009 06:20pm | #9

          as always I'm glad I posted. Thanks for the replies and the links to those websites - I would have just asked for double pane low-E glass and thought I was getting the best. I haven't met with the glazing contractor yet, as is usually the case my initial conversation with him did not give me a huge comfort level but we'll see when I meet him tomorrow. Regarding the lower awnings, they are wood frame and I think I would probably eventually replace them once I have some extra $$$. As far as replacing the upper windows myself, I'm going to see what the cost of having it done by the glazing contractor will be. Installing the new panels is not so much my concern as is removing the existing glass without killing myself. Also - right now my whole house is in some stage of being renovated (note the woodshop set up in my living room in the first photo) and we haven't had a real kitchen in about 14 months, so its time to start prioritizing projects and subbing some out before I find myself on the outside of those windows looking in at my angry significant other. For the record - its not a great view at the moment, I'll need to do some serious landscaping if I don't want the neighbors and every car that passes by to know exactly what I am up to. Eventually though....

          1. dejure | Feb 25, 2009 11:27am | #14

            If memory serves me, thicker glass helps, but I've had a coffee break then, so I'll have to be retrained as to the actual improvements. At any rate, going back to school days, dead air space is your friend. There isn't any with single pane, so the more dead air space gaps, the better. If I was way north and not feeling broke I'd look at the triple glaze units. I got a ridiculous deal on crates of glass that were ordered in error. They were all mirror, tinted and 1/4" glass (they were free and the smallest was 3'x4'). I enclosed a basement in a house I was renting. All the other windows were single pane. The difference was notable. You didn't feel the chill off the double pane units, but just walking past the others chilled you enough they always got plastic in the winter.

          2. Clewless1 | Feb 25, 2009 04:05pm | #15

            Hopefully I'm not jumping into the middle of a concept and destroying it here.

            Thicker glas UNITS help ... that is the overall thickness of a double glazed unit whether it uses 1/8, 3/16, or 1/4" glass means little in the overall performance.

            Your 1/4" glass ... are you talking about double glazed units (mirror/tinted) that were made of 1/4" glass? 1/4" glass for that size of glazing sounds like a lot.

          3. dejure | Feb 25, 2009 09:42pm | #16

            These were crates of glass an architect ordered for a sky scraper project. However, they were the wrong specs, or something, so I ended up with seven crates, free. They were so heavy, my 10,000 pound goose-neck trailer was pressed to haul them. They were all two plates of 1/4 inch glass. The little 3'x4' I used on a former landlord's rental had some real weight (somewhere between one hundred and a hundred fifty pounds) to it when I lifted it into place. That was without any framework, which I had to fabricate from 2x's.

            Edited 2/25/2009 1:43 pm ET by dejure

        2. Jay20 | Feb 25, 2009 01:33am | #11

          I printed your procedure and going to try it this spring. Thanks Jay

  2. rlrefalo | Feb 24, 2009 03:39am | #2

    Sean, there are films that can be applied to the glass that are supposed to reduce heat loss, similar to low e type glass. Might be worth a look.

    Rich

    1. Clewless1 | Feb 24, 2009 04:02am | #3

      doubt it. A solar film MAY affect u-value, but only slightly, I think.

  3. Clewless1 | Feb 24, 2009 04:12am | #4

    Definately a good move and since they are 'site built' relatively inexpensive and easy to do. Don't assume you can't upgrade the lower operables (BTW they are "awning" style). Check into it. Might be able to replace stops and install thicker glass. Are they aluminum framed? Might consider buying replacement windows for them.

    As far as glass ... minimum 3/4" overall glass thickness; low conduction glass spacers, AND low-E glass ... that should be your minimum requirement.

    Yes, you should feel a big comfort difference. Bigger if you e.g. used Heat Mirror glass ... which if available for a reasonable price, I would DEFINATELY consider. Why? VERY good U-value (0.25 or lower), VERY GOOD comfort, VERY BIG single glass area. Long term comfort and savings. I would enccourage you to at least compare prices. Don't be surprised if the glass supplier has no idea what Heat Mirror is. For a north facing wall, you would do clear, no tint (same for low-E).

    This is a large area of glass ... worth your while to go the extra mile (I should be in advertising?!). Always a good opportunity for some good changes. I hope you have a great view you are preserving.

  4. Jay20 | Feb 24, 2009 05:08am | #6

    A few thoughts. Because of energy issues the Federal Government has issued minimum heat loss standards for new construction I think starting in 2010. Because of that there is a lot of pressure on window manufacturers to improve their products. Kind of the low hanging fruit to accomplish the requirements. I would guess windows will be getting much more efficient in the next year. Windows are expensive and if you can wait you could be a whole lot better off. Right now foam filled fiberglass frames are the most efficient and weather proof. If you like wood on the inside many manufacturers are adding stainable wood vernier to the inside. There are lots of choices in glass. The two most efficient systems out there now are 1) Triple pane dual low e coated argon filled units or 2) a new approach to heat mirror films between the glass. A couple of web sites to look at are http://www.efficientwindows.org and http://www.alpeninc.com  Hopes that helps.

    1. Clewless1 | Feb 24, 2009 09:14am | #7

      Don't you mean maximum heat loss standards?

      If you want you can get window U-values under 0.10. One poster mentioned it a month ago. It uses like double and triple Heat Mirror mylar films plus low-E coating on the glass as well. This has been technology available now for 25 years.

      1. Jay20 | Feb 25, 2009 01:46am | #12

        Your correct and I remember the post. I investigated the information and the glass manufacturer claimed a U value of .05. They manufactured the glass and heat mirror membrane only and provided a list of window companies they sold to. I also saw some information that a glass manufacturer invented a glass panel with millions of small bubbles in it. They were so small that they did not effect vision through the window. The U value was incredible. The issue was trying to manufacture the product on a mass bases. They thought they might be in production by 2011.

        1. Clewless1 | Feb 25, 2009 08:14am | #13

          If you find a local dealer who can order it ... you can order just the glass. And yes, you can get some VERY good U-values if you want ... it's a matter how many films of mylar you want to use and the combinations w/ e.g. low-E coating on the glass and gas fillings. This is technology that has been around and in use since the early 80's (when I first was introduced to it shortly after the first large commercial project used it.

          I've seen Heat Mirror used on a large commercial project as recently as 1995 by a speculative developer. I've used it myself. I've not heard of the other technology you mention ... that is, I'm surmising 'cutting edge' technology that is not readily available on the market.

          1. Jay20 | Feb 26, 2009 12:14am | #17

            The issue in the past with Heat Mirror was the channel the glass is set in failed and Heat Mirror got a bad name. That has now changed.  The other technology has been bouncing around labs for a wile but they never were able to make it for the market. One of the larger glass companies is claiming they are close to doing that and has started to build a factory to manufacture it. Just read the info some place. Jay

          2. Clewless1 | Feb 26, 2009 05:34pm | #18

            I've heard that. The edge spacers have always been 'standard' to my understanding. They look typical. Without quality control, there was definately the potential for leakage/failure. My experience is that these problems were never very pervasive and there was always a warranty. One of the first buildings ever done had several thousand sqft of windows and they never had problems with them.

            Heat Mirror IMO is a top quality product, it is to bad that more mfg. facilities aren't available to manufacture it. There are only a handful in the entire country. The easy low-E coated glass quickly overshadowed the market ... even though Heat Mirror was really the original application of low-E coatings.

            I hope to see it make a comback. With the right market demand and quality control, it is strong competition for standard low-E coated glass. Better performance at a slight premium.

          3. DesignBuild | Feb 26, 2009 10:20pm | #19

            anyone care to give me a gut check on the price? $33.00 sq/ft for 1" thick, low-E, argon filled double-pane glass. Includes removal of existing single pane glass, supply and install of the new panels, one-year warranty. Re-install/replacement of interior wood stops by yours truly.Without argon it goes down to $30/sq - without Low-E it goes down to $21.Take into account I'm in Northern NJ where everything costs more than it should.

          4. Clewless1 | Feb 27, 2009 09:25am | #20

            I'd say that fixed windows (glass and frame) of vinyl would GENERALLY run maybe say $8-12 a sqft .... w/ low-E glass. Tinted a little more. That's materials, uninstalled.

            I'd say shop and get a solid range of prices. That sounds a bit high for sure.

            In other words ,,,, sounds like you got a bid from an outfit that is REALLY busy and doesn't need your business. I've  seen vendors/contractor overbid if they are really busy (to the tune of 2-3x, even).

            Edited 2/27/2009 1:29 am ET by Clewless1

  5. migraine | Feb 24, 2009 07:17pm | #10

    I recently did a similar job like this house.  14" trippled brick built with recessed exterior windows.  The windows were each individual one piece, four wide with a muttin separating the upper payne and lower payne. 

    We cut out the horizontal muttin and used fixed paynes in the uppers and single hung in the lowers.  These were factory mulled as a single one piece unit, but 4 individual units wide.(10'w x7'h)  Three rooms like this, among many others.

    Used stucco finned retrofits with a pvc trim between the windows and sealed with a white urethane chaulk.  PVC stucco mold on the exterior sides and top.  PVC base trim at the bottom with weep holes just in case moisture got behind the trim.

    The interior trim was replaced.  New interior jambs with casing and protruding sills. Small crown detail below. 

    Removing and installing the windows were a lot less work the the interior trim and painting

    The job was in NorCal with extreme summers and a south/southwestern exposure.  Made a huge difference in the cooling $$$ last summer.

    Had a local glass company stop by and take pictures.  He said he had one coming up just like this.  Wonder if I'll get credit for my work or him      ;)

    I priced them out through a few distributers, but HD was quite a bit cheaper after getting their volume contractors pricing.  Shorter lead time too and absolutely now errors or problems.

  6. artworks | Feb 27, 2009 04:46pm | #21

    Not shure of the 'degree days' of heating you have but looking at frames on the window unit, I think best course would be a complete window change, frame and all. I have done change similar with 1 helper in a good day, casings and all. 

     Yes you can change single galss to thermopane or even tri-pane. Take off old moulding / stops, usually break and have to replace, apply new glasing strip inside and out to mouldings, clean up frame, repair any rot ( lots by the look in pic) pick up broken glass ( at least l unit)  I would figure at least 3 hrs a unit. 

     You might be able to modify opperating units to accept dual pane, but I doubt that hardware will be enough to handle the extra weight.

    You will be ALOT more comfortable sitting / standing in front of a dualpane / tripane window than a single, &  a lot less condensation also.

    IF IT WAS EASY, EVERYONE COULD DO IT!

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