I have a home in Birmingham, AL, with 21 (single-pane wood) windows that I’m trying to replace. I am going with double pane vinyl replacement windows, with low-E glass and argon-filled. All windows that I have had quoted from installers meet the energy star guidelines for this area. Life should be good, but based on the quotes I’ve received and the description of work, I’d like to pose some questions to the experts:
1. One installer offers a window with a “heat mirror” film that is centered between the two panes. The windows with the film deliver significantly better U-factor, noise reduction, and UV block than the windows without it – even better than triple pane, Low-E, argon-filled, at least based on the spec sheet. While these numbers may hold true at the factory, I’m concerned that the film won’t last or perform long-term. Anyone had any experience with these type of windows and/or films (Brand: Kensington with Heat Mirror)? I’m leaning toward the no-film models.
2. With replacement windows, is there an effective way or even a need to waterproof the rough opening? I have seen numerous products advertised in the magazine that show a sloped rough sill drain, or details where the builder sloped the rough sill and installed a bituminous membrane (Rick Arnold & Mike Guertin) for new construction. I presume such a detail is problematic for window replacement projects.
3. Should I specify that a closed-cell foam membrane and/or insulating foam spray be installed in the gaps around the windows to completely fill the space between the backside of the brick mould and interior trim? Omit the foam at the sill if you sloped the rough sill above in #2? When asked, all indicated they sealed the gap in some way or the other, but not one detailed it on their work estimates.
4. What’s the best way to trim the exterior of the new window? I have one installer recommending that I replace all the existing wood brick mould with an all-vinyl brick mould. Sounds better than what’s there, but I’m concerned about keeping it watertight with movement that may take place. The rest recommend cladding the existing brick mould with a variety of options: one with boxed vinyl trim that doesn’t come close to matching the contour of the exsiting mould (sounds like a leak); one with painted aluminum that is to be bent to match the exact profile of the existing brick mould; one with vinyl-coated aluminum cladding; and one clad emphasizing that the top and bottom cladding would be cut overlength, be clipped and bent vertical at the ends so that the side cladding would cover the top and bottom and not rely solely on a butt-cut and caulking at cladding corners.
5. If insulated vinyl frames are superior to hollow frames, is it worth me trying to spray insulating foam (the DAP kind that doesn’t warp the frame) in the open cells of the window frames when they drop off the windows, or am I asking for trouble?
6. What details or requirements do you consider a must for replacement window projects?
Thanks in advance for all the good information! As you can see, I am lost without it.
Replies
I can help with some of this. Other parts I defer to my colleagues with more knowledge.
1.) Heat Mirror is a wonderful product. It lasts well, and the U-value is fantastic. No more condensation on your glass.
2.) Water management is always critical at windows. I defer to others on the specific details.
3.) I prefer the foamed in place. It firms up the window, but must be done skillfully or it can bow the jambs inward.
4.) Defer.
5.) Sounds like trouble to me. Probably voids the warranty. Not worth it.
6.) The new windows need to look right for your home, work well, and never leak water. Flashing details are the most critical.
Bill
Have you considered renovating your existing windows? that's what the house came with, they fit right, and are probably properly installed.
Take the sashes out, remove all the paint and glazing, prime the sashes, reglaze, paint. New ropes (or chains) and maybe some new pulleys.
Seal around the trim to keep air infiltration out.
Probably cheaper than replacements.
You do know that the seal on those double pane windows will fail, don't you? What is the guarantee on them? 20 years if you are lucky? Do you really want to replace windows every 25 years or so?
My single pane windows have lasted 105 plus years. They should go another 100 years.
Have you considered renovating your existing windows?
That's almost always the best option. If you add a storm window to a single pane window, you achieve comparable or better U value and thus energy savings than the best replacement windows.
Don't want to rag on the OP but its got to cost an arm and a leg to replace those windows with decent vynil units. If the exisiting are not shot why does he want to replace them? Has he figured out that he'll never repay the cost of the windows in energy saved?
Its not super fun work but rehabbing your own windows plus adding storms is just so much more cost effective.
Daniel Neumansky
Restoring our second Victorian home this time in Alamdea CA. Check out the blog http://www.chezneumansky.blogspot.com/
Oakland CA
Crazy Homeowner-Victorian Restorer
$60000 in the glass alone for a sunroom??Yee gads! Both my houses didnt cost that.
Has he figured out that he'll never repay the cost of the windows in energy saved?
I doubt it - and the replacement window industry won't tell him that. They are more focused on selling windows with bogus "energy savings tests" and other techniques to lead the unsuspecting buyer into believing that replacement windows will save energy and/or pay back the cost over their life (they won't do either, in fact).
BTW, recent surveys show that refurbished original windows in pre-1960's houses increase resale value, replacement windows decrease resale value. Something to think about if one wants to sell the house one day.
Has he figured out that he'll never repay the cost of the windows in energy saved?
I doubt it - and the replacement window industry won't tell him that. They are more focused on selling windows with bogus "energy savings tests" bogus energy savings tests? such as? and other techniques to lead the unsuspecting buyer into believing that replacement windows will save energy and/or pay back the cost over their life (they won't do either, in fact). Again, I invite you to share your numbers that prove the assertion that replacement windows won't save energy over the orginal windows.
BTW, recent surveys show that refurbished original windows in pre-1960's houses increase resale value, replacement windows decrease resale value. Something to think about if one wants to sell the house one day.
Do you happen to have references to these surveys? I would like to read them.
I'm no big fan of plastic windows but the sad truth is most people today are a bunch of trifling fat slobs who cant clean their house or their yard let alone ever paint or open a window. This is why vinyl windows are necessary.
This article cites one of the original studies, done at Oak Ridge Labs, in 1999.http://www.homeenergy.org/archive/hem.dis.anl.gov/eehem/00/000711.html
Good morning,
From the article that you posted:
Although new, high-performance windows are the ideal, simply putting up storm windows in the wintertime can be a very effective alternative (italics mine)
And I have certainly never denied that storm windows are an excellent idea and that they will significantly upgrade single lite performance.
From my very first post on this subject:
But, restoration and the addition of a good storm window can still be a huge improvement over windows that are stuck, painted-over, drafty, and without storms and it will keep those windows out of the landfill.
Again I think that we have tended to wander a bit out of sight of the original post. No where in any of my posts did I ever suggest NOT restoring windows. I simply said that high-end newer windows will outperform (energy considerations) exisiting single pane and storm combinations. This is simply true - all rhetoric aside. The evidence to support that claim is readily available thru government, university, and industry studies.
As I said in the original post as well, I happen to like older windows - good ones, not the junk from the 50's and 60's (and even into the 70's and 80's). And by junk I happen to include dual pane windows as well as single pane. There were good windows made during that same timeframe and there were junk windows made as well.
In fact, my previous house was built in 1905. It needed a good bit of work when we moved into it - particularly because it had been subjected to a 1960's "remodel" - we know how those often went! Even to a carpeted bathroom (ended up replacing the entire subfloor from that one!).
The remodel included adding a master bedroom / bath / dining combination. The addition included very basic builder grade single pane windows with storms. They were junk - likely cost all of $19.95 when new. I replaced them and it was worth every penny for cost savings and especially comfort..
But, in the original portion of the home, we had the original (in some cases very large) double hungs with rope and pully and seasonal storm / screens.
I never considered changing those windows. Well, except every fall when I was on a ladder on a windy day changing the screens for storms - then I cursed them and promised to replace them in the spring...obviously it never happened.
The first winter in that home was cold! The windows were not tight and they needed maintenance badly. But, I was very fond of those windows and since they were "part of the home" one of the very first jobs I did that spring was to repair the storms and screens (they needed it badly) and scrape and repaint the windows - including adding new weatherstripping where needed and replacing a couple of cracked lites.
Because of my industry affiliation I have access to restoration glass which mimics the original panels. In fact, it is made by exactly the same process. That was much better than replacing with plexiglass (which we have all seen) or even with float glass. But upgrading those windows involved a conscious decision to maintain the integrity of the home knowing that I could get better performance if I replaced them because I work with that information every single day. But replacing was never an option for me.
Edited 10/2/2007 7:18 am ET by Oberon
I love restoring windows. It is very satisfying as a properly "tuned" weighted double hung works better than any new window i have worked with.
I don't recall the OP mentioning why he wanted to replace his windows (just energy savings? Totally rotted out?).
I also don't recall the OP mentioning how old these windows are or if they are an important part of the design of his home.
Original windows in a turn-of-the-century Victorian are a long way from a 1950's or 60's ranch.
Personally, I happen to really like old windows. I believe that they are so much a part of the charm of an older home that it is worth every possible effort to try to save them. And while I certainly understand the appeal of replacing windows for the potential improvements in energy consumption, comfort, and the ease of maintenance, I also understand the desire of many people to try to do everything possible to save the original windows in a classic home.
There are a lot of misconceptions floating around about old windows versus new windows and wood windows versus vinyl windows versus aluminum versus fiberglass - and often many opinions are based on feelings and not on facts - that come up in discussions like this one. I would offer a few comments for consideration: Fact – if a homeowner was to opt for top-quality replacement windows, he or she could get them made in any style that they wanted – styles that would fit their home and that would be virtually indistinguishable from the original windows in the home – and, these windows could last every bit as long as your home. Note that I said "top-quality" spelled $$$$$$$$.
Fact – a low end replacement window doesn’t come close to meeting the same sort of standards as does a top-quality product – from the materials used, to the glass used, to the hardware used – it could be like comparing a Yugo to a Ferrari (and whatever happened to Yugo BTW?) – and from a performance standpoint a good restoration will often be a much better investment of time, trouble, and money. The guy in the Sunday paper who promises to replace every window in a home at "$99.95" with his "super-dooper-highest-quality" vinyl or aluminum window likely has neither the highest quality window nor does he have the homeowner’s long term interest at heart. He needs to get in and to get out – and what happens in five or 10 years? That’s no longer his problem. Common comment – restoring a single-pane window and storm window combination will result in energy performance numbers that are comparable to any new window on the market regardless of any glass coatings or gas used with the new window. Fact – the newest dual or triple pane windows made with LowE2 or LowE3 coated glass and argon or krypton fill are substantially more energy efficient than old windows – single or double pane. A triple pane window with LowE2 coating on surfaces 2 and 5 combined with krypton gas infill and a low conductance spacer system can achieve energy performance numbers as much as 10 times better than an original single pane window and as much as six times better than a single pane with storm (or a low-end dual pane window as well). Common comment – old windows may have lasted 50, 75, 100, or more years and new windows will always fail in short order only lasting 5 or 10 years. Fact – quality products will outlast non-quality products no matter when produced. For all of the older windows that are on homes today and that deserve the chance to be around even longer, there are tens-of-millions of windows that were made in the last few centuries that didn’t make it into today’s world for a wide variety of reasons – including simple window failure – often as a result of poor or non-existent maintenance. The ones that have made it thru are often the best that were produced and they likely had a good bit of maintenance at some point. These are all very good things that makes the idea of keeping them around even longer worth serious consideration. Ultimately, older windows have lasted as long as they have because they are of simple, uncomplicated construction that has had the distinct advantage of using a material (old growth lumber) that is no longer widely available. The pyramids will easily outlast a modern skyscraper – that doesn't make a pyramid inherently superior than the skyscraper - it is simply different. The better, newer, dual and triple pane window systems now on the market and installed all over Europe and <!----><!---->North America<!----> should easily reach 50 years life expectancy - many will go well beyond that time. There are vinyl windows in <!---->Europe<!----> that were installed over 50 years ago that are performing flawlessly after that long a period. Common comment – restoring old windows is good for the environment and helps with energy performance. Fact – while this is certainly true, it isn’t the entire story. Despite comments from folks who love their old windows – and there are a variety of very good reasons for that feeling – those reasons are primarily aesthetic, not primarily efficiency. Replacing older windows with available high-end energy-saving products will directly save energy over restoration. But, restoration and the addition of a good storm window can still be a huge improvement over windows that are stuck, painted-over, drafty, and without storms and it will keep those windows out of the landfill. Fact – many old houses have their original windows and some of these windows (if they have had adequate maintenance for their lifetime) are in very good shape. And some are also in very poor shape, most are somewhere in between. But, they have all made it this far and if they are worth restoring, then by all means that should be considered as a very definite option. Again, most (but not all) older windows are made with old growth lumber which is inherently better than almost any lumber available today - which while being absolutely true and rather sad in some ways - in the end this is what our ancestors left us with – kind of wondering what we will be leaving our descendents?. Fact – older single pane windows with sash cords are inherently huge energy wasters. because that open spot where the weights hide is an energy black-hole. There are alternatives to the sash-weight pocket that will greatly improve this energy dump – but while replacing the sash cords and weights and then insulating the space will improve energy performance not everyone considers that a viable option. It is possible to (somewhat) insulate the space even with sash cords and weights present - and every little bit helps.Fact – many people like the look of wavy glass which was the norm in windows made long ago yet the waves and bubbles in glass are technically a flaw in the manufacturing process. Glass producers did their best to avoid such embellishments, but it was the best that could be mass produced at the time using the sheet glass process. Actually, for higher-end (spelled $$$$) folks they could produce glass without the waviness, even back at the turn-of-the-century, but it was expensive and few folks wanted to, or could afford to, spend the money for it, which of course doesn’t mean that such ornamentation doesn't add the charm and character of the window and subsequently the home. Lots of "flawed" items have a certain charm and character of their own. And btw, I very much like "flawed" wavy glass – and it is available today, made in the exact same process that was used 100 years ago, only today it is considered decorative and is therefore expensive.
Edited 9/26/2007 9:20 pm ET by Oberon
Common comment – restoring a single-pane window and storm window combination will result in energy performance numbers that are comparable to any new window on the market regardless of any glass coatings or gas used with the new window. Fact – the newest dual or triple pane windows made with LowE2 or LowE3 coated glass and argon or krypton fill are substantially more energy efficient than old windows – single or double pane. A triple pane window with LowE2 coating on surfaces 2 and 5 combined with krypton gas infill and a low conductance spacer system can achieve energy performance numbers as much as 10 times better than an original single pane window and as much as six times better than a single pane with storm (or a low-end dual pane window as well).
There are a number of independent test reports available that disprove that claim. That thermopane windows can perform better than a single pane window with a storm window is a very common misconception, but unfortunately it is not accurate. Even the very best replacement windows have an equivalent R value no more than 6 or so. An original single pane window, properly maintained, with a single pane storm window easily exceeds that.
One of the biggest problems with replacement windows is that they are almost never installed correctly. Take your R6 window, leave a 1/16" gap on one side of the frame - i.e. if the frame does not fit perfectly - and your R6 window will achieve something in the range of R1.
BTW, that's why the window industry adopted U numbers - because the R value of even the very best windows is so abyssmally poor. A window is a hole in the wall, no matter what you do.
Part of the limitation of thermopane windows is the size of the air space. If you made a thermopane window with a 2" air space between the panes, you could theoretically approach the performance of the window/storm window combination. Unfortunately, that's not practical, so thermopane window makers resort to "tricks" and exotic techniques to get closer to the performance of windows with storm windows. Ultimately, however, the simple single pane window and storm window with a 2" or more airspace outperforms thermopane windows. Basic physics, unfortunately, dictates that.
Even if an excellent quality multi-pane window out performs an old window, how much it does so and what it is worth depends on the climate and the cost of energy. A window that is twice as efficient probably still does not save very much energy in a mild climate.People can get caught up in these numbers, and lose sight of the fact that it is actual energy usage that matters. And the energy usage is defined a lot by how well the installation is done and how the area AROUND the window is sealed, rather than the properties of the window itself.
Even if an excellent quality multi-pane window out performs an old window, how much it does so and what it is worth depends on the climate and the cost of energy. A window that is twice as efficient probably still does not save very much energy in a mild climate.
Agreed, and the OP appears to be in a fairly temperate climate. Cooling is likely more of an issue than heating.
That is one area where newer materials can excel - reducing solar gain. However, there a number of very effective films than can be applied to either storm windows or the single pane windows to reduce the solar gain.
Common comment – restoring a single-pane window and storm window combination will result in energy performance numbers that are comparable to any new window on the market regardless of any glass coatings or gas used with the new window. Fact – the newest dual or triple pane windows made with LowE2 or LowE3 coated glass and argon or krypton fill are substantially more energy efficient than old windows – single or double pane. A triple pane window with LowE2 coating on surfaces 2 and 5 combined with krypton gas infill and a low conductance spacer system can achieve energy performance numbers as much as 10 times better than an original single pane window and as much as six times better than a single pane with storm (or a low-end dual pane window as well).
There are a number of independent test reports available that disprove that claim. That thermopane windows can perform better than a single pane window with a storm window is a very common misconception, but unfortunately it is not accurate. Even the very best replacement windows have an equivalent R value no more than 6 or so. An original single pane window, properly maintained, with a single pane storm window easily exceeds that.
You are correct that a good dual pane replacement window can achieve an R-6. Where you are incorrect is that a single pane with storm can exceed that number...it can't. The R-value of an 1/8" single pane 1/8 is R-1. Add the storm window and the R-value jumps to a whopping R-2. Some people will argue that the single pane with storm can get to R-2.5 or even R-3 - which I don't agree - but even then it isn't near an R-6.
What many (most) people don't realize is that the dual pane window was developed to equal the performance of a single pane with storm without having to have "two" separate parts of the window. So technically it is incorrect to say that the single pane with storm is just as efficient as the dual pane. It should be said that the dual pane is just as efficient as the single pane with storm - but, that is a simple dual pane window with made with two lites of clear glass and without the "bells and whistles".
And do you happen to have references to those independent test reports? I would be interested in reading them.
One of the biggest problems with replacement windows is that they are almost never installed correctly. Take your R6 window, leave a 1/16" gap on one side of the frame - i.e. if the frame does not fit perfectly - and your R6 window will achieve something in the range of R1.
I agree 100% that installation is vital to a ensuring window performance. If any window (or door, or cabinet, or applance, etc) is installed poorly the performance is going to suffer. However, to say that an R-6 window is going to be something like R-1 is meaningless unless you have numbers to back up that claim. Remember that R-value is based on resistance to conductive heat flow and technically R-value does not take either convection or radiation heat loss or gain into its measurements (I know, there are "weighted" tables available and that ASHRAE Fundamentals book covers it as well), but ultimately R-value is simply resistance to conductive heat flow. Generally R-value numbers when dealing with windows are based on center-of-glass readings and do not take into account overall unit performance.
BTW, that's why the window industry adopted U numbers - because the R value of even the very best windows is so abyssmally poor. A window is a hole in the wall, no matter what you do.
You are incorrect that window companies use U-factor as a "cover-up" for poor R-values.
In fact, U-value (U-factor for windows) has been around very much longer than has R-value. U-value was developed by engineers for measuring the actual heat flow thru a material - or group of materials acting together. Unlike R-value, U-value does take into account both convection and radiation losses and gains - which if one were to consider window performance in total makes a great deal of sense, Windows pass direct solar heat - radiation. Windows, whether dual pane or single pane with storm, have a habit of developing convection currents between the lites - not to mention contributing to convection currents in the home as well.
Part of the limitation of thermopane windows is the size of the air space. If you made a thermopane window with a 2" air space between the panes, you could theoretically approach the performance of the window/storm window combination. Unfortunately, that's not practical, so thermopane window makers resort to "tricks" and exotic techniques to get closer to the performance of windows with storm windows. Ultimately, however, the simple single pane window and storm window with a 2" or more airspace outperforms thermopane windows. Basic physics, unfortunately, dictates that.
Again, that is not correct. The optimal airspace for energy performance for any dual clear glass combination is about 1/2" - whether dual pane or single pane and storm. Above that, there is no particular advantage in energy gain. Above 7/8" the performance will actually start to decline very slightly because of those pesky convection currents that I mentioned earlier. As the space becomes wider, the energy performance continues to decrease.
If you wish to discuss basic window physics, we can certainly do that -
The only way for a top-end multipane window with LowE and argon or krypton fill to approach the energy performance of a single pane with storm - is to leave the dual/triple pane window open because otherwise the new widow will outperform the single with storm just as I stated in my original post.
Edited 9/28/2007 6:58 am ET by Oberon
Where you are incorrect is that a single pane with storm can exceed that number...it can't.
The optimal airspace for energy performance for any dual clear glass combination is about 1/2" - whether dual pane or single pane and storm. Above that, there is no particular advantage in energy gain. Above 7/8" the performance will actually start to decline very slightly because of those pesky convection currents that I mentioned earlier. As the space becomes wider, the energy performance continues to decrease.
If you have papers or other reference that show this information, I would be very interested in reading them. This information contradicts the accepted data developed by old house pros, and also conflicts with the research I have done on my own home. To date, I have not seen any report that shows a thermo pane window exceeding the performance of a window/storm window combination with a 2" air space.
One of the non-intuitive aspects of storm windows is that a bit of airflow actually improves performance. Wood storm windows tend to rot and decay if there is no airflow, so they are generally designed to have a bit of airflow. Conventional wisdom is that this airflow would decrease R value, but in practice it seems to improve it slightly.
One interesting reference on the practical issues in improving energy performance in older homes is Charles Wing "Housewarming with Charlie Wing", which was also made into a PBS series. A companion book, "From the Walls In", goes into much more detail.
Everything I've ever read about glass R-values pretty much agrees with Oberon--and I think he's even a little "optimistic".<accepted data developed by old house pros, and also conflicts with the research I have done on my own home. >Just about the only data I think worth looking at comes from scientists and testing labs.
GIGO.
I think one issue that we will not be able to get around is that you mention a book by a home "restorer" and also research you do on your own house. Common sense and conventional wisdom don't mean much when trying to develop perfomance criteria.
In my case, this is what I do - I work in the glass industry in the areas of testing, certification, product performance, product development - all interrelated areas.
The US government has spent a great deal of money researching these areas.
http://www.energystar.gov/index.cfm?c=windows_doors.pr_anat_window
Universities have studied these issues - I have posted links to some of that research.
http://www.cbe.berkeley.edu/research/<!---->pdf_files/SR_NFRC2006_FinalReport.pdf
http://www.efficientwindows.org/lowe.cfm - this was done by the University of Minnesota - I suspect that they know something about heating requirements
The window and glass industry has many many millions of dollars in research supporting the information that I have stated -
1/8" glass has an R-value of 1 and by adding a second lite in a storm window it gives you an R-2 - period. In addtion, strom windows are designed to "leak" otherwise you have moisture build up between the storm and the single pane which results in condensation on the storm if the single pane is also loose. If the single pane is tight enough then that condensation forms on that surface.
Assuming that the older windows don't allow enough moisture to escape - necessitating a humidifier in the home - so that there is no build up of condensation on the windows. Unlikely in really cold environments because the inner pane will get cold enough to condensate at very low moisture levels.
Dual pane windows with LowE2 and argon reach R-6 and triple panes with LowE on two surfaces and krypton fill reach R-10. Look it up. The numbers are on line. These are not made-up numbers, they are real -
Performance Properties
Monolithic Clear Glass
Clear Glass IG Unit
Clear Glass and Solarban¯ 60 (3) Glass IG Unit
Air Fill
Air Fill
Argon Fill
Ultraviolet Light Transmittance
82%
67%
13%
13%
Visible Light Transmittance
90%
82%
74%
74%
Insulating Properties Winter Night U-Value Winter Night R-Value
1.13
0.88
0.49
2.04
0.30
3.33
0.24
4.17
Shading Coefficient
1.01
0.89
0.45
0.45
Indoor Glass Temperature (Winter Night -°)
16.6°
45.3°
54.4°
57.1°
3.0 mm glass (1/2" airspace in insulating glass (IG) units.)
Performance Properties
Monolithic Clear Glass
Clear Glass IG Unit
Clear Glass and Solarban¯ 60 (3) Glass IG Unit
Air Fill
Air Fill
Argon Fill
Ultraviolet Light Transmittance
80%
64%
10%
10%
Visible Light Transmittance
90%
82%
73%
73%
Insulating Properties Winter Night U-Value Winter Night R-Value
1.11
0.90
0.49
2.04
0.30
3.33
0.24
4.17
Shading Coefficient
1.00
0.88
0.44
0.44
Indoor Glass Temperature (Winter Night -°)
16.8°
45.4°
54.4°
57.1°
I know, it is all a scam by the window and door and glass companies, but here are a few reports anyway from the largest residential glass company in the world...
http://www.cardinalcorp.com/technology_casestudies/roseville.htm
http://www.cardinalcorp.com/technology_casestudies/windrose.htm
http://www.cardinalcorp.com/data/RedBookHTML/index.htm
For every "Charlie Wing" that you may quote (and I know who he is), I can produce many times that amount of controlled study material - both lab and field work - but ultimately it doesn't matter because folks will believe what they believe -
and if a few old house pros know more than literally hundreds of researchers armed with million dollar budgets and state-of-the-art facilities - then I need to find a new job.
Edited 9/28/2007 10:03 am ET by Oberon
Edited 9/28/2007 10:16 am ET by Oberon
There are serval very important points that need to be made about vinyl windows:
1) Lifetime warranties - usually only valid for the current owner who has the windows installed - is an extrapolated number. We did the same thing in the steel industry for corrosion resistant coatings on steel - subject them to extensive testing and harsh climate conditions for 6 months or a year and then extrapolate. Non one knows how long vinyl windows will last in part because the composition keeps changing - vinyl comes from oil and oil is getting more expensive and disappearing. Window manufacturers are trying to protect themselves from a disappearing raw material.
2) Vinyl windows can only have minimal repairs - replacing a spring or a latch. Once a screw strips out you are stuck with replacing the sash and or the entire frame. Anchors and screw grommets are only temporary - long term, you end up replacing.
3) We are in a period where people don't open their windows very much - use the climate control. But as energy costs go up, more people will be opening their windows for air circulation - and vinyl windows, no matter how well they are tuned are not meant to be continuously opened and closed. And invariably, the upper sash starts to drift down - and you tighten the spring - and it sill starts to move down! As the population ages, folks opening these windows will have an increasingly difficult opening them - and none are easy to tilt open to clean (but then today's society doesn't look upon window cleaning as a necessary task).
As a "semi-retirement" job, I am responsible for the maintenance of a large complex for retired folks. About 10 years ago, the person then in charge decided to replace all the windows with vinyl ones - over 500. And I now have to repair them - and trust me, I've seen plenty of split, cracked and faded vinyl windows on product less than 10 years old. Our residents have a difficult time opening the windows - I am constantly trying different spring systems to make the opening easier.
And there is a small part of the complex that was originally a home for a wealthy family - built in the early 1900's. I keep the wood windows in this section well tuned with good jamb sealant and properly installed storms. The residents lament why they can't have the old windows that open and close so smoothly (chain and weights)!
As with anything of value that you buy, you should be extremely thorough investigating your potential purchase - be it a belt sander or a kitchen mixer or replacement windows. Pull the financials and credit rating on the manufacturer - how long have they been around? Who owns them? Do you get a parts catalogue with the windows? Are there 1, 2 and 5 year reference installations that you can visit to see if they are performing? Folks will spend months investigating recip saws before buying but for some reason are ready to plunk down thousands based on a salesman's's pitch - buyer beware!
I think one issue that we will not be able to get around is that you mention a book by a home "restorer" and also research you do on your own house.
FWIW, Charles Wing is an MIT engineering professor and a recognized expert in this field. His publications, while often written in a more accessible format, are well supported by extensive research. While John Leake is an "old home restorer", he is also a nationally known expert in this field. He's one of the folks the government researchers go to for answers. Robert Yapp is another source of confirming research.
My home may be the most researched home in America :-) The research on my home has provided the data for many publications.
The primary problem with much of the government research is that they often ask the wrong questions. They get good answers to those questions, but it's not the right question. The right question, IMHO, would be "how does the performance of single pane windows with storm windows compare with high tech thermopane windows, in a real world application?"
As an researcher in the engineering field, it seems I spend half my life explaining why a government sponsored test report doesn't mean or prove what the lay person thinks it does.
In my case, this is what I do - I work in the glass industry in the areas of testing, certification, product performance, product development - all interrelated areas.
It might have been prudent to mention your industry affiliation earlier in this thread. One would expect that since you are in the industry we are talking against, that your position might cause your perspective to biased to that industry. We all have biases, of course - I just personally think the "emperor has no clothes" is particularly strong in the window and glass industry.
Edited 9/28/2007 1:42 pm ET by woodturner9
As with anything of value that you buy, you should be extremely thorough investigating your potential purchase - be it a belt sander or a kitchen mixer or replacement windows. Pull the financials and credit rating on the manufacturer - how long have they been around? Who owns them? Do you get a parts catalogue with the windows? Are there 1, 2 and 5 year reference installations that you can visit to see if they are performing? Folks will spend months investigating recip saws before buying but for some reason are ready to plunk down thousands based on a salesman’s pitch - buyer beware!<!----><!----><!---->
ETG, I could not agree more. My wife happens to know someone who just plunked down $16,000 for new windows because a salesman convinced her and her husband that they needed to replace their windows. These windows were less than 10 years old and there was nothing major wrong with them. The salesman convinced them that they could “go after” the company that made the original windows because of the 20 year warranty.
They no longer have the units. The replacement guys took them away – but they did get pictures and they expect the original company to compensate them for the cost of the new windows – ain’t gonna happen.
As you said, some people will investigate a new tool (I am currently doing it with a dovetail jig – anyone happen to have any good suggestions?), while others might plop down $16,000 on a “whim”. Amazing.
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Okay, one thing I think I have been seeing in these posts (my take only – and not suggesting for anyone else), is that everyone seems to be thinking “double hung with ropes and pulleys” for older windows and that replacement automatically means vinyl window.
I don’t believe that I ever was that specific in my posts – other than possibly in the original – if so it was unintentional. I have been discussing generic glass performance – not specifically vinyl or wood or fiberglass, or aluminum, or any of the composites – not even specific to a window style either.
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Woodturner,
FWIW, Charles Wing is an MIT engineering professor and a recognized expert in this field. His publications, while often written in a more accessible format, are well supported by extensive research. While John Leake is an "old home restorer", he is also a nationally known expert in this field. He's one of the folks the government researchers go to for answers. Robert Yapp is another source of confirming research.<!----><!---->
I have heard of both Charles Wing and Robert Yapp. I have never read anything by Mr. Wing, but I have read a few things by Mr. Yapp – and I readily admit that I didn’t necessarily agree with everything he had to say. But in some areas we were in agreement as I recall.
I have exchanged emails with John Leake. He contacted me a few months back and asked permission to quote me in some of his future publications. We exchanged a bit of technical information and had what I considered to be a very enjoyable visit; but I had to decline when he wanted to know who I was and because of that he probably won’t be using any information that we exchanged - and we certainly did not agree on every point that we discussed. Feel free to ask him about it if you would like.
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The right question, IMHO, would be "how does the performance of single pane windows with storm windows compare with high tech thermopane windows, in a real world application?" <!----><!---->
I am not sure how to answer that one – the entire point is that is exactly the question that has been asked. There are reams of paper and a herd of electrons floating around with that exact question – and the answer is always “not very well” – there is no realistic comparison between the high tech and the single lite with storm. The thermopane window with LowE coating and gas fill will – in all cases – significantly out perform the single pane and storm.
Real world testing, lab testing, computer simulations – they all have the same result – and the technical information is out there – it is simply a matter of reading it.
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It might have been prudent to mention your industry affiliation earlier in this thread. One would expect that since you are in the industry we are talking against, that your position might cause your perspective to biased to that industry. We all have biases, of course - I just personally think the "emperor has no clothes" is particularly strong in the window and glass industry.<!----><!---->
Why would it have been prudent to mention that I work in the glass industry in order to comment on glass performance? Other than to promote myself as an “expert”, I suppose – something that I do not do willingly when answering questions or trying to help people on line. In most cases it is simply unimportant – a non-issue.
Perhaps you are right and I should have done so – and obviously I am biased, but that bias is based on many years of technical research into this area. I do happen to have extensive knowledge of glass and window performance – possibly as much or perhaps a bit more so than those folks that you mentioned earlier – and if I don’t I happen to have an answer I know, and work with, people who do.
(specific background information has been removed - I placed it here for a one-day "read" and not for posterity)...
And one could argue that none of that background information is really very important to this discussion – (and for all you know, and perhaps believe, I made it all up anyway) – which is ultimately simply a difference of opinion about fenestration performance. Although to be frank one side is heavily represented by science and technology with a good bit of supporting evidence; while the other is primarily “common sense” and with a few books and opinions of some “vocal” experts. But that’s what makes a discussion like this fun.
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My home may be the most researched home in <!----><!----><!---->America<!----><!----> :-) The research on my home has provided the data for many publications.<!----><!---->
That is really interesting. Why is your home so well studied? Can you mention some of those studies and who is actually doing them? Again, I very much enjoy reading about such things. <!----><!---->
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What I'm saying is that the difference in cost between rebuilding existing wood double hung windows-installing a storm window and installing fancy new triple-pane windows is so great that the HO will never ever even break even on their 'investment'. Now if I have windows and RO's that are rotted beyond reasonable repair that's a different story. But replacing serviceable wood double-hungs with fancy new windows is a non starter financially. Unless ya gotta burn gold to heat your house or something...
I am often asked about payback by folks who are considering changing their windows. Funny thing is that I had the same discussion with John Leake a few months back – and I am going to paste my comments to him at the time –
I am asked on occasion how much money would a homeowner save in energy costs by replacing all of the windows in their home. My advice to said homeowner is that before even considering any such project consider a complete energy audit on the home to see how the complete system is working; and where it may not be working very well. Often, in an older home the windows really aren't a significant contributor to the (lack of) energy performance of the home; and time and effort (and significantly - money) can be better spent on other considerations. I suggest that in my opinion, window replacement is not the panacea that sales folks often make it out to be. <!----><!---->
John, the report mentioned $1200 for a lab-performed energy audit of a window. I would suggest that that cost is about double (or more) today and it is available thru several test labs that I can think of off-the-top-of-my-head. But again, I would question the eventual practicality of such testing because first, when the "restoring versus replacing" argument comes around to the energy performance differences (if any) between the restoration window and the replacement window, they will be lost in the rhetoric of the aesthetic reasons for restoring versus replacement and second, because no matter what the numbers show about individual unit performance, ultimately the individual window is still part of the overall structure and its performance as part of that overall structure is what is important - not necessarily how well does it perform in the lab environment. Now since I work in a lab, and I perform testing on window systems in that lab, I am not suggesting that lab performance is meaningless. But I am suggesting that, like automobile mileage ratings, window (or other component) energy performance numbers are very much subject to real world conditions and should be evaluated under those conditions. Laboratory performance testing and ratings are important and there are huge amounts of data available to prove that there are direct correlations between laboratory performance testing and actual real world performance, but this validity is based on the results of thousands of test samples and comparing a few random samples here and there and then to arrive at definitive conclusions about that performance would be questionable.
I am NOT a salesguy. I don’t sell anything. If someone wants to replace their windows and they live in a 1920’s Victorian, then I tell them that I think that they are making a huge mistake. But if they live in a 1950’s ranch, and the original windows are pretty much worthless, then I would probably help them in selecting the correct replacement windows for their needs. Different strokes.
I could certainly say much more – but this is way too long already.
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Edited 9/30/2007 10:32 am ET by Oberon
The thermopane window with LowE coating and gas fill will – in all cases – significantly out perform the single pane and storm.
As I said previously, that is the opposite of what I have read in all the objective lab testing I have seen (and done). Why don't you link an example or two so we can discuss specifics?
Glass, by its nature, has very little insulating value. A sheet of double strength glass (3.0mm or 1/8"), alone, has an R-value of about .8 to 1 depending on thickness. And while an R value measurement for a specific window may include both glass and frame (but, only when it was calculated using U value measurements) it ususally is only a measure of center-of-glass. With a good solid sash and frame and a good storm window over a single pane window, you can get an R-value of approximately 2 - maximum.
A good dual pane IGU (Insulating Glass Unit) with a softcoat LowE coating and an argon gas infill can potentially get about an R-6. A triple pane IGU with a krypton gas infill can achieve an R-10 - again, these are center-of-glass readings.
But as I mentioned earlier, R-value is not the best measure of a window’s performance, and not because U-value is it is a way to "hide" poor performance numbers. U- value is a much better measure for measuring window performance (whole house performance as well, but the fiberglass insulation folks have conditioned people to think in R value…).
R-value is based on Resistance to heat flow. Heat always goes to cold unless acted on by an outside force - second law of thermodynamics.
Heat travels in three ways – conduction, radiation, and convection. Conduction is the transfer of heat thru a substance by atomic or molecular interactions…simply put, when you touch the metal handle of a frying pan on the stove and the handle is hot, then you are experiencing conduction heat transfer. Convection is transfer of heat energy thru mass motion of a fluid (yes, air is a fluid) resulting from the movement of the heated fluid from the source of the heat. An example is warm air rising and displacing cooler air which then falls and warms up and then rises replacing…etc.Radiation is heat transfer by the emission of electromagnetic waves which carry energy away from the emitting object. In other words, when you stand in direct sunlight and you become warm, you are being warmed by radiation. While both conduction and convection need a medium (see above explanations) to transfer heat, radiation works even in a vacuum – which is good because otherwise we would not be here discussing this!
A single window with very poor insulating properties will potentially be affected by all of those factors. Sealing the window will help against air leaks but that has little affect against a very real and significant part of energy loss which is the glass itself.
As I mentioned earlier, windows are normally measured in U-values and not R-values.
U value measures how much heat is passed thru an object, or said another way, how much heat an object will pass; versus R-value which is resistance to heat flow. Although it doesn't sound like much of a difference, it does come into account much more when doing actual energy performance calculations.
In the real world when it is 70 degrees inside your home and zero outside the center-of-glass temperature of a single pane window is going to be about 16 degrees. If the window is howling it is going to be less. If the sun is shining directly on it it is going to be more. But, 16 degrees is an average.
If you add a storm window that center-of-glass reading is going to jump to approximately 43 degrees - which is a very nice improvement, no doubt about it.
If you replace the single pane and storm with a clear-glass dual pane, then your center-of-glass reading will be - approximately 43 degrees. Again, the performance should be very similar and testing in the real world shows that it is.
In both of these cases - and in the case of every window built (and walls as well if we want to get specific), the center is warmer and the edges are cooler. So when I say 43 degrees at center-of-glass, it needs to be remembered that the edges are lower.
If that dual pane has a LowE coating and an argon gas infill then the center-of-glass temperature will be about 57 degrees – a 14 degree improvement over a clear glass dual pane or a single pane with storm window – but again, and more importantly, there will be a comparable edge of glass improvement as well, particularly if the IGU (Insulating Glass Unit) was manufactured using a warm edge spacer system.
These are real numbers.
When light strikes an object, one or two or three of three things will happen. The light will (a) reflect from the object, (b) be absorbed by the object, or (c) pass right thru the object.What the light does in a specific circumstance is dictated by both the “substance” of the object and also by the frequency or wavelength of the light. The differences between a brick wall and a glass window are obvious examples of the “substance” of different materials affecting light differently, but also different wavelenghts of light will react differently to different objects as well.When dealing with windows (or any light-passing / light-blocking material) we are dealing with three frequency-ranges of light – we define those different frequency ranges as UV or ultraviolet, visible light, and IR or infrared.
These three "divisions" of light are based primarily on whether or not we can "see" the light. Nature does not divide up the spectrum to suit us. At the far end of the UV spectrum we wander into X-rays. At the far end of the IR spectrum we will find microwaves. Anyone shop for an oven recently? You might find that among the "newest things" in oven technology is IR/microwave oven cooking.Typically we think of IR as being the source of “heat” on our world. And while IR is the primary source of heat, ALL light carries a certain amount of heat energy – if you have light entering your home, you have heat entering your home. How much heat is entering (or leaving) is what concerns folks in most cases. Solar heat gain…can be a good thing in winter in Minnesota and can be bad thing in summer in Arizona. And conversely it can be a good thing in an Arizona winter as well as a bad thing in a Minnesota summer. What is the best way to get solar gain – which may be a positive or a negative depending on whether you want it or not – well thru clear glass is probably atop the list.
Better stop since this is getting long - and anyway, I have to head for work. Have a great day!
But as I mentioned earlier, R-value is not the best measure of a window’s performance, and not because U-value is it is a way to "hide" poor performance numbers. U- value is a much better measure for measuring window performance (whole house performance as well, but the fiberglass insulation folks have conditioned people to think in R value…).
I assume you would agree with the definition of U value:
U= 1/R
Given that they are the inverse of each other, how can one be a better measure than the other? They seem to be simply a different interpretation, with no additional information in either one.
I just reread this mornings post. I was rushing when I wrote it and it shows…very sloppy. <!----><!----><!---->
I will try to avoid that this evening.<!----><!---->
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While it is absolutely true that R value and U value are inverse - 1/R = U and 1/U = R, they are not really the same and there are several reasons why window ratings are correctly given using U-value (actually U-factor for windows) rather than R-value.<!----><!---->
R-value measures the thermal resistance of a material while U-factor measures thermal transference thru a material.
Again, R-value measures the thermal resistance of a material while U-value measures thermal transference thru a material. <!----><!---->
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The formula for computing U-value is: Btu / (hr x degrees F x sqft)<!----><!---->
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The formula for computing R-value is: (hr x degrees F x sqft) / Btu<!----><!---->
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Calculating both U-value and R-value are based on one sqft of insulation (type and thickness of the insulation are not important for the illustration). <!----><!---->
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With a temp of 70º on one side of the insulation and 0 º on the other we can determine the U-value if we know how much energy it takes to keep the 70º side at 70º for one hour. If it takes 3.68 Btu’s to keep the 70º constant for that hour, then we have 3.68 / (1 hr x 70º x 1 sqft) = a U-factor of .05257.<!----><!---->
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Using the same scenario, the calculation for R-value would be (1 hr x 70º x 1 sqft) / 3.68 or an R-value of 19.02. But the difference is we that determined the actual heat loss to find the U-value and we calculated the resistance to heat loss to find the R-value.<!----><!---->
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Since 19.02 = 1 / .05257 or .05257 = 1 / 19.02 - R-value and U-factor do have an inverse or reciprocal relationship….<!----><!---->
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As generally used, R-value can be defined as a theoretical number. R-value is based on the assumption that the material(s) used in an application will actually achieve the results that they are capable of achieving in that situation. <!----><!---->
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In other words, if a certain thickness of insulation has an R-value of 19, then filling an entire wall cavity with that thickness of the material will result in a wall with an R-19 insulating value…true? Well, not really since the R-value only accounts for resistance to heat flow of that particular insulation and does not account for any variations across the wall surface. <!----><!---->
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While R-values can be added together to arrive at the total thermal resistance when going outside to inside thru a wall – for example, siding + sheathing + insulation + drywall = a given R-value – measuring energy performance across a wall surface must be done using U-value measurements. R-value cannot be used to calculate heat loss across a wall surface.<!----><!---->
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Imagine a single wall in a home that is 100sqft. For this example we are going to assume that this wall has an R-value of 10 – R-1 for sheathing, R-8 for insulation, R-1 for drywall. For this illustration we are going to ignore the effects of studs (etc) and just say that out wall averages R-10 across its total surface. Simple…<!----><!---->
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Now we are going to add a 5’x 2’ (10sqft) window to this wall and we are going to assume that this window has an R-value of 1. <!----><!---->
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So in this scenario what is the overall R-value of this wall?<!----><!---->
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If we wanted to rate the entire combined average by adding (90sq/ft x R-10) = 900, + (10 sq/ft x R-1) = 10, we would arrive at 910/100sq = R-9.1 avg. However, this is not correct since heat follows the path of least resistance which is not addressed in strict R-value calculations – calculations which (yet again) are based on resistance to heat transference and not on actual heat loss. (There are weighted tables in the ASHRAE Fundamentals handbook for this type of problem).<!----><!---->
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Well, the R-10 is converted to U-0.1 and the R-1 is converted to U-1.0. If we combine (90sq x U-0.1) = 9, + (10sq x U-1.0) = 10 – giving us 19 – and then we divide that by 100sq/ft – we arrive at a U-value of .19. We then convert back to R-value and we have an R-value of 5.26 – which is correct for that scenario – and that means that our little window (10% of the overall wall surface) has reduced the wall's overall thermal resistance by almost 50%!<!----><!---->
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See the difference? While we can use R-value to better visualize the energy performance (which is why R-value was developed in the first place); we need to use U-values to properly calculate that performance.<!----><!---->
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Well, converting to U-value for the calculations – R10 wall is again U-.01, but now the window is U-.2. Calculating (90sq x U-.1) = 9, + (10sq x U-.20 ) = 2 gives us 11, divided by 100sq = U-0.11per sq/ft which then converts to an R-9.09 overall for the wall surface. <!----><!---->
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Edited 10/2/2007 8:33 pm ET by Oberon
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So in this scenario what is the overall R-value of this wall?<!----><!---->
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If we wanted to rate the entire combined average by adding (90sq/ft x R-10) = 900, + (10 sq/ft x R-1) = 10, we would arrive at 910/100sq = R-9.1 avg.
But that's not how R values are aggregated. R value is analogous to electrical resistance in parallel, and is aggregated the same way: Rtotal=1/(1/R1 +1/R2 + 1/R3)).
If you use the correct formula and do the math correctly, you will get exactly the same answer.
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See the difference?
Sorry, no. You seem to have confirmed my comment that it doesn't really matter. There is not any additional information in U value vs R value.<!----><!---->
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Rtotal=1/(1/R1 +1/R2 + 1/R3)).
You are correct that the formula that you have presented will work - but it only works because 1/R = U. You have just demonstrated exactly what I was saying - look at the formula and what it is showing - Rtotal=1/(1/R1 +1/R2 + 1/R3)) or Rtotal = 1/(U1 + U2 + U3)....You have changed the R to U and back again to R with that formula. The figures show U-value calculations.
But that's not how R values are aggregated.
Again you are correct for the same reason. You must use U-value to measure performance of disparate materials. R-value doesn't work - unless you convert to U-value first - which is what the formula that you just presented does.
Edited 10/8/2007 8:51 pm ET by Oberon
Ever get the feeling you are trying to push a rope?
Ever get the feeling you are trying to push a rope?
Not really, just working through the engineering/scientific process (though I realize the healthy debate inherent in engineering discussions may seem like arguing to non-engineers).
In my opinion, if you can find a way to put your bias aside, you will be able to learn a great deal from Oberon.Oberon, thanks for your patience and generosity here and elsewhere on the internet.
In my opinion, if you can find a way to put your bias aside, you will be able to learn a great deal from Oberon.
Well, you are certainly entitled to your opinion. I'm not sure what bias you are referring to, since I really don't have a bias other than a preference to make decisions based on objective fact rather than industry hype.
It appears you have formed a judgment regarding Oberon's knowledge level in this area and my own. I'd be very interested in what led you to those conclusions, in the one day you have been a member here (BTW welcome to the forum!). I assume you are aware of the origin of the name Oberon, as it is used to refer to a "playful deceiver". Makes one wonder if his board name was chosen as a hint.
I haven't really read enough of Oberon's posts to form an opinion of his level of expertise. I have read many of his posts on BT, and myself and others have noticed several fairly basic discrepancies between his views and accepted mechanical engineering fact. You may want to read more of his posts. I am concerned, for example, about the apparent confusion between R value and U value. That's pretty basic stuff any mechanical engineer would understand, and on the face of it, suggests he might be "stretching" his knowledge.
So I'm having some trouble reconciling what appear to be some fairly basic misunderstandings with the authoritative tone of his posts. None of this is meant to be judgmental or unkind, I'm simply observing that the posts seem to suggest limited experience and knowledge. Part of the problem, of course, is that anyone can post anything on the internet, so it can be difficult to validate the knowledge level of any poster (including myself).
I know what my level of knowledge and experience is, so obviously I can trust that more. In spite of all the dismissive comments sometimes offered by the jealous, I would have have earned even a single Ph.D if I didn't "have a clue". I can of course learn from anyone, but I want to learn fact and truth, not error.
So as we discuss this more, hopefully we will be able to resolve the discrepancy between his posting and implied knowledge and experience level. Maybe at that point we can decide who should be teaching whom ;-)
Edited 10/10/2007 12:21 pm ET by woodturner9
Edited 10/10/2007 12:24 pm ET by woodturner9
Edited 10/10/2007 12:35 pm ET by woodturner9
I have read your posts giving electric advice here... My money is on Oberon.
I have read your posts giving electric advice here... My money is on Oberon.
You might want to stay away from gambling :-)
I wish the original poster had come back. The "save the windows" group assumed he had no storms - just because he didn't mention them doesn't mean that he doesn't have them - and that the old wood windows are reparable. They've also assumed that s/he wants to replace them because that person is (a) lazy (b) uninformed (c) an easy mark for a salesman. S/he obviously doesn't know that s/he will NEVER make back his investment! How about putting assumptions aside for a moment?
Old quality windows sure are nice - smooth action, lovely warm looks, but brrrr sooooo drafty in the window. Let's put some nice ugly storms up in front of them and totally ruin the look from the street, shall we? No? Then how about interior storms? I had some of those (with your 'ideal' 2" of space between) and the entire north side of my house spent the winter dripping from the condensation between the two panes of glass. Then there is the fact that unless you have permanent storms (as I did), you need to spend every fall and spring doing them. Some people on this forum have posted about building accessible homes for the aging years. So we can have a nice home with wide doorways, lever knobs, roll in curbless showers, but twice a year somebody needs to climb a ladder and mess with the storms.
While single panes with storms can be a great solution, I wish the "save the windows" crowd would stop being so judgemental with the small amount of information they have.
Old quality windows sure are nice - smooth action, lovely warm looks, but brrrr sooooo drafty in the window. Let's put some nice ugly storms up in front of them and totally ruin the look from the street, shall we? No? Then how about interior storms? I had some of those (with your 'ideal' 2" of space between) and the entire north side of my house spent the winter dripping from the condensation between the two panes of glass. Then there is the fact that unless you have permanent storms (as I did), you need to spend every fall and spring doing them. Some people on this forum have posted about building accessible homes for the aging years. So we can have a nice home with wide doorways, lever knobs, roll in curbless showers, but twice a year somebody needs to climb a ladder and mess with the storms.
It seems you are making a many assumptions there.
Old windows, properly maintained, are not drafty at all.
"Invisible storm windows" are essentially invisible - they don't really alter the appearance.
If you are getting condensation between the storms and the windows, the storms are not properly vented (a common problem, as the knowledge of how to maintain windows has been "lost").
There are many ways of installing storms that do not require them to be removed and installed twice a year. The traditional one is a mechanism rather like a box lid bracket - the bottom of the storm swings out when you want ventilation, swings back in and locks when you want the window closed.
I just wish the "replace the windows" crowd would stop being so judgmental with the tiny amount of information they have :-)
When I think it, it is a reasoned arguement, when you think it, it is being judgemental :)
I'm not a "replace the windows" crowd - but the "save the windows" crowd seemed a lot louder, so I thought I'd throw my oar in. We had interior storms - the only way to "vent" them would be to the interior of the house, which is where the moisture comes from. It was a poor design, and makes my point that storms are not always the answer, and neither are replacements.
makes my point that storms are not always the answer, and neither are replacements.
Agreed - the "best choice" depends on the indivdual circumstances. Replacement windows aren't always a bad choice, and restoring original windows is not always a good option.
but the "save the windows" crowd seemed a lot louder
One other point I forgot to mention:
The "camp" that gets a lot of us old house folks excited is the "replace good old wood windows with cheap vinyl windows for only $9.99" - it's the cheap vinyl windows often sold as the universal answer to everything that are particularly annoying. In contrast, if one is installing $1000 Marvin historical replica wood windows, it's really tough to say they aren't comparable or better to the original wood windows.
I totally agree - replacing good windows (wood or otherwise) with cheap ones is tragic. In an historic home the consideration to replace should be heavily balanced with preserving the qualities of the home, which often means saving the windows. It just seems that many people pile on the "save the windows" bandwagon whenever someone mentions replacing their old windows. Keeping in mind that most houses in this country were built after WWII, the decision to replace can be the right one. Those of us with houses built in the 50's and onward often did not get the careful crafstmanship that went into homes in earlier eras.
In my case, I replaced aluminum sliders and interior storms with double-paned insulated vinyl. They sure look a lot nicer and function much better - I'll continue my "research" this winter and see if the condensation problem on the north side of the house has been solved. The cost to me for purchase and installation was about 3% of what I paid for the house 9 years ago, and less than 2% of my last appraised property tax value. And that was for the most expensive vinyl window with a real representative around here.
Dude... The one single statement in this entire thread where you blew it was...
If you have papers or other reference that show this information, I would be very interested in reading them. This information contradicts the accepted data developed by old house pros, and also conflicts with the research I have done on my own home. To date, I have not seen any report that shows a thermo pane window exceeding the performance of a window/storm window combination with a 2" air space.
I'm not a gambler.
and also conflicts with the research I have done on my own home.
Why does that statement concern you so much? The house was purchased in large part to be a laboratory for practical building research. The research on my home has generated a great deal of published research, and some of those papers are commonly cited in this area.
If you look at the government reports, they typically do the same thing - test a handful of houses, often as few as one.
It's also common for researchers to do this - Charles Wing's publications (he was a professor at MIT who was instrumental in dispelling many of the myths about insulation, windows, etc. with objective fact obtained via research) are perhaps the best known example.
If it makes you more comfortable, I can do research on your house :-) Assuming you don't mind living in a research lab environment, of course :-)
I assume you are aware of the origin of the name Oberon, as it is used to refer to a "playful deceiver".
You have read your Shakespeare!
Actually, I started using Oberon (a long time ago) on line simply because I liked the sound of it. In fact, I was teaching astronomy at the time and as I am sure that you know Oberon is the largest moon orbiting Uranus - so there certainly was a bit of whimsy in the name selection. As well, I am a huge fan of Roger Zelazny's "Amber" series which has a major character named Oberon as well.
No deeper meanings than that.
I have read many of his posts on BT, and myself and others have noticed several fairly basic discrepancies between his views and accepted mechanical engineering fact. You may want to read more of his posts. I am concerned, for example, about the apparent confusion between R value and U value. That's pretty basic stuff any mechanical engineer would understand, and on the face of it, suggests he might be "stretching" his knowledge.
Would you care to elaborate on "others" and "basic discrepancies"? Who? When? Where? I would never suggest it doesn't happen - I have been in a few good discussions, as have most of us here, but as said in that paragraph is very unprofesional in my professional and personal opinion.
fairly basic misunderstandings with the authoritative tone of his posts -
So as we discuss this more, hopefully we will be able to resolve the discrepancy between his posting and implied knowledge and experience level. Maybe at that point we can decide who should be teaching whom
Implied knowledge??????????
No comment.............I did reply with very specific comments. I removed them since at the moment my comments cannot be constructive.
Hey, I made it all up - but I also listed formulas and references and "researchable" information that is available to anyone - whereas the replies to my comments often referred to "common sense", "conventional wisdom", and "my house"- and comments that government research (for example) is inadequate based on I-am-not-sure-what available data.
I would suggest it isn't my understanding of these concepts that is questionable and I would leave it to anyone following this thread to draw their own conclusions...
Edited 10/12/2007 7:58 am ET by Oberon
Edited 10/12/2007 8:02 am ET by Oberon
Edited 10/12/2007 8:35 am ET by Oberon
Edited 10/12/2007 8:40 am ET by Oberon
but I would suggest it isn't my understanding of these concepts that is questionable
When you suggest that taking the reciprocal of a number "adds information", that seems to suggest a basic misunderstanding of mathematical operations. A misunderstanding that basic causes one to question other information posted as well.
I'm really curious about your background, now. Feel free to send me an email, if you like. Sometimes people "come across" differently online and in writing in ways that can be misleading. At the moment, you remain an enigma to me :-)
When you suggest that taking the reciprocal of a number "adds information", that seems to suggest a basic misunderstanding of mathematical operations. A misunderstanding that basic causes one to question other information posted as well.
I'm really curious about your background, now. Feel free to send me an email, if you like. Sometimes people "come across" differently online and in writing in ways that can be misleading.
Okay, based on the last few posts, I think that I see what is happening here.
I never intentionally suggested that the reciprocal of a number adds anything. I have tried to show in my posts that in the case of U-value and R-value they are used differently and that they convey different aspects of performance - just as in an electrical circuit resistance and conductance do the same - I truly am not sure where it came across that I was suggesting other than that, but my posts can be long and I can tend to wander a bit at times in them since I write them off-the-top-of-my-head and I am not a great proof-reader when I post on line.
Based on that, I can see why you might have been puzzled in that case.
Makes much more sense now.
I went back and read our exchange and found this one which may be an explanation of sorts...
(you) 3. R=1/U, so neither R value or U value add any additional information, but one or the other may be preferred in some circumstances by some people or by convention.
(me) And here I disagree 100% with the first part of your statement (and agreed with the second part)
I think this is a good example. You did say add any additional information which in the context that I intended was not as you intended...
In the window world, R-value can be, and often is, used to signify the center-of-glass performance of the unit. So, salesfolks will often suggest when selling a window that a particular window has an R-value of 8 (for an example). But, the U-value for that same window might be actually .33 (again, for example).
And while BOTH numbers are technically correct, the inverse of R-8 is not U-.33 and so we have an apparent problem - perhaps a paradox even.
R-8 is center-of-glass performance (absolutely correct) and U-.33 is overall unit performance (again, absolutely correct). We have two different values for the same subject and yet both are technically correct.
Now while the R-8 CANNOT be translated to a U-value to represent the overall performance of the window, the U-.33 CAN be changed to an R-value of 3.03 which although it isn't really the best way to present window performance, it can be easier for the average person to understand. While R-8 certainly does not equal R-3.03, both numbers do represent different aspects of the window energy performance.
So from my perspective U-value can be considered to add additional information from R-value in this case - IF the R-value is based on center-of-glass performance and not overall performance.
The same would be true of a wall - such as in the explanation I dropped in another post.
Although R-value can be used to correctly calculate performance (as in the formula that you showed), it may not be correct depending on how calculated - and it has to be converted to U-value to actually do some, but not all, performance computations -whereas U-value has to be correct because of the way it is calculated.
That is what I was thinking when I responded to your post. As you said, it can be difficult to understand what the other person is suggesting on line.
Per your comments on the posts from "Street", at first glance I started to take some significant offense to your implied suggestion; however if the situation were reversed I might have had the same thought as well, so I quickly became unoffended (is that a word?).
I have no idea who "Street" is and never specifically noticed that there were two posts from that individual - until you mentioned it. As to being new, again, I happened to notice that you mentioned it in one reply but I didn't really pay attention to that consideration at all.
Edited 10/12/2007 10:07 pm ET by Oberon
And while BOTH numbers are technically correct, the inverse of R-8 is not U-.33 and so we have an apparent problem - perhaps a paradox even.
I think I see what you are getting at now, and that makes sense. Thanks for the clarification.
You actually keyed it in when you mentioned different people reading different things from the same information. That's why I went back to reread (again) the long exchange - then it made sense.
It would have been a lot easier if I would have thought to begin the discussion between R and U with the same explanation...oh well, live and learn
Holy Cr@p You Guys Need To Get A Room Or Something!!!
Daniel Neumansky
Restoring our second Victorian home this time in Alamdea CA. Check out the blog http://www.chezneumansky.blogspot.com/
Oakland CA
Crazy Homeowner-Victorian Restorer
LAUGHING! well, just trying to keep it professional!
thanks and you are welcome
It's very interesting that the Streets account is a new account, apparently created to post two messages praising you on this thread - and no other posts. One might be suspicious of "pumping" from such a sequence of events.
Sometimes I think that I am just not getting my point across...I sit back and try to think how else to put it.
You are correct that the formula that you have presented will work - but it only works because 1/R = U.
It seems we are debating semantics at this point.
It appears to me we agree on the following points:
1. R value is commonly used for insulation values, such as the insulation value of a wall. The formula for aggregating R values is Rtotal=1/(1/R1 +1/R2 + 1/R3). Note that in practice when calculating the R value for a wall, for example, area must be considered - a 2" R-0 hole in the wall does not limit the wall R value to 0 (but does reduce the R value more than one might expect).
2. U value is commonly used for windows and similar components (for whatever reason, we disagree on the historical reasons for this choice). U values can be aggregated by simple addition, but again area needs to be included to give accurate results.
3. R=1/U, so neither R value or U value add any additional information, but one or the other may be preferred in some circumstances by some people or by convention.
It seems we are debating semantics at this point.
No, it truly isn't semantics - R-value and U-value are different.
R-value NEEDS U-value to "work" in the context that it is often used - determining wall, or window, or whole house energy performance. Without U-value, R-value in that context is meaningless.
U-value does not need R-value. It is a "stand-alone" measurement/formula.
You introduced a great analogy when comparing R-value to an electrical circuit. To foloow up with your analogy I would offer that while R-value represents resistance to heat flow (as I have previously mentioned), U-value represents transmittance or "current flow" of thermal energy.
I don't believe anyone would consider resistance and current in an electrical circuit to be representitive of the same force - only stated differently.
1. R value is commonly used for insulation values, such as the insulation value of a wall. The formula for aggregating R values is Rtotal=1/(1/R1 +1/R2 + 1/R3). Note that in practice when calculating the R value for a wall, for example, area must be considered - a 2" R-0 hole in the wall does not limit the wall R value to 0 (but does reduce the R value more than one might expect).
I agree 100%.
2. U value is commonly used for windows and similar components (for whatever reason, we disagree on the historical reasons for this choice). U values can be aggregated by simple addition, but again area needs to be included to give accurate results.
Again, we agree 100%. But with the caveat that U-value was developed in the 1930's and R-value in the 1970's. U-value is stand alone formula for determining thermal transference - while R-value was developed as a means to quantify thermal resistance of specific materials such as fiberglass insulation.
R-value is simply easier for the lay-person to "picture" performance (often incorrectly unfortunately) while U-value is used for actual thermal performance.
3. R=1/U, so neither R value or U value add any additional information, but one or the other may be preferred in some circumstances by some people or by convention.
And here I disagree 100% with the first part of your statement but agree 100% with the second half.
Have a great evening!
And here I disagree 100% with the first part of your statement but agree 100% with the second half.
Fair enough. I guess we will have to "agree to disagree" on that one. From an engineering viewpoint, though, neither contains more information than the other (R value vs U value), since they are simply reciprocals of each other.
To foloow up with your analogy I would offer that while R-value represents resistance to heat flow (as I have previously mentioned), U-value represents transmittance or "current flow" of thermal energy.
I'm uncomfortable with that analogy - it's sort of mixing apples and oranges. Resistance is R, measured in ohms, and is analogous to R-value. Conductance is analogous to U value, and is measured in mhos. Conductance = 1/R.
And here I agree 100% - we beat that horse dead into mud...there ain't nothin left
(Oberon) To foloow up with your analogy I would offer that while R-value represents resistance to heat flow (as I have previously mentioned), U-value represents transmittance or "current flow" of thermal energy.
(Woodturner) I'm uncomfortable with that analogy - it's sort of mixing apples and oranges. Resistance is R, measured in ohms, and is analogous to R-value. Conductance is analogous to U value, and is measured in mhos. Conductance = 1/R.
apples and oranges? You said it yourself - simply repeating what I had already said - R = resistance. U = conductance.
As you said, conductance does indeed = 1/R... just as U = 1/R
So if I follow what you have said throughout your posts, electrical resistance and electrical conductance are the same thing because they are inverse?
So if I follow what you have said throughout your posts, electrical resistance and electrical conductance are the same thing because they are inverse?
They are not the same thing, but neither one has more information than another. Maybe another analogy will help - if you have 0.5 of a pie, or half a pie, you still have the same quantity of pie. They differ only by a mathematical operation - you don't have more pie because of the math operation.
In the same way resistance and conductance, and U value and R value, differ only by a mathematical operation. Thus they one cannot have more information than the other, it is simply a different way of interpreting the information.
Edited 10/13/2007 8:39 am ET by woodturner9
Woodturner, you said to Oberon:
It might have been prudent to mention your industry affiliation earlier in this thread. One would expect that since you are in the industry we are talking against, that your position might cause your perspective to biased to that industry. We all have biases, of course - I just personally think the "emperor has no clothes" is particularly strong in the window and glass industry.
I enjoy reading your posts and I enjoy reading Oberon's posts but don't you think you've gone too far with this personal attack? Oberon had no obligation to disclose this in his posts and anyway he disclosed it voluntarily. You immediately assumed that this affiliation makes him biased -- which could easily be flipped toward you in that your engineering affiliation somehow makes you biased.
Apparently you're a scientist so keep it technical and leave the personal attacks to lawyers and others who know how to make them effectively (sorry, I couldn't help it).
Billy
It might have been prudent to mention your industry affiliation earlier in this thread. One would expect that since you are in the industry we are talking against, that your position might cause your perspective to biased to that industry.
I enjoy reading your posts and I enjoy reading Oberon's posts but don't you think you've gone too far with this personal attack?
I certainly did not intend it as a "personal attack", and I'm sorry if it seemed that way.
We all have biases and perspectives, and tend to unconsciously "spin" what we write, to some extent. My preference is to restore old windows, and my bias reflects that - I cite information that supports my view, I interpret ambiguous comments in a ways that supports my view, etc. Oberon works in the glass industry, so one would expect that employment to influence his views to some extent. That's not a judgment or a personal attack, just an observation of human nature.
Edited 10/1/2007 3:27 pm ET by woodturner9
Billy,
A sincere thanks for the support, but I never took Woodturners comment as any sort of personal attack. I truly saw it as I think he intended it - which was just as an added bit of information...
But in all seriousness, I appreciated your comments as you read the question.
Thanks
Oberon
Oberon,
I appreciate your matter-of-fact comments and discussion of both lab research and real world experience on the window threads. Thank you.
Billy
You are welcome. I am also enjoying this discussion.
Thanks Woodturner. Maybe I jumped in too quickly, and I'm not the "police" around here.
Anyway, you and Oberon have a good discussion going one here, and it's good to see the research behind the comments. Obviously there are lots of factors to consider, and it's a real challenge to design controlled experiments that account for and test the various factors.
Billy
Wow that's a lot of good info you got there. Regarding the 'great window conspiracy' comment. I'm not saying that fancy new super-expensive windows won't save more energy.
What I'm saying is that the difference in cost between rebuilding existing wood double hung windows-installing a storm window and installing fancy new triple-pane windows is so great that the HO will never ever even break even on their 'investment'. Now if I have windows and RO's that are rotted beyond reasonable repair that's a different story. But replacing serviceable wood double-hungs with fancy new windows is a non starter financially. Unless ya gotta burn gold to heat your house or something...
I am inundated with ads from window installers touting their new 'energy saving' windows but my above point is never really spoken of...
Now if I lived on a busy-noisy street triple panes might be worth it just for the noise reduction.
Daniel Neumansky
Restoring our second Victorian home this time in Alamdea CA. Check out the blog http://www.chezneumansky.blogspot.com/
Oakland CA
Crazy Homeowner-Victorian Restorer
Actually, while some folks will suggest triple pane glass for its sound deadening ability, and while triple pane may be a slight improvement over standard double pane at certain frequencies - if the center lite is a different thickness than the surrounding lites - and then given the additional density because of the extra lite; overall there is no difference in STC rating between triple and double pane provided that the overall airspace between the panes is constant between the two constructions.
In other words, consider a triple pane with two 1/4" airspaces and a dual pane with a single 1/2" airspace...both using 1/8" glass...the STC will be identical if the IGU's are the same dimensions.
Sorry, I couldn't resist!
Edited 9/29/2007 8:23 am ET by Oberon
Hi Roof Drip,
Heat Mirror has been around since the late 70's. Many companies used to carry it, but relatively few do so today. Heat mirror has had a history of problems related to the film "wrinkling" between the lites due to both interior (between the lites) heat issues as well as the significantly different rates of expansion and contraction between the glass and the film. In addition, Heat Mirror has had a history of seal failure due to the same issues.
Southwall Technologies, the maker of the Heat Mirror system, has claimed that they have fixed these issues in recent years, but I know that a good many window companies are still paying claims based on using this product and it does not have a particulary "good name" in the window/glass industry.
I am not an installer, so I will avoid the installation questions to the experts in that area.
Insulated frames have slightly better R-value performance than do hollow frames. But, even small gaps in the insulation negates much of that advantage. I would not even consider trying to DIY insulating frames in your window for a number of technological reasons - and like was said in a previous post - there goes the warranty.
We had "Heat Mirror" glass in our Four Seasons Sunroom, built in '90; less than 10 years later, we had $60K of glass replaced because all the units were failing. Four Seasons covered about 1/2, plus the labour
Phill Giles
The Unionville Woodwright
Sounds to me like you know more than the window tin men that are around here. If I were you, I would buy the windows yourself and put them in. A decent vinyl 36 x 54 runs around 175, add for low e 20, add for grids between glass 25, add for someone slse to wrap the frames with a brake 30 each. I've put over a thousand vinyl replacement windows in, its really dumb work. Simonton makes a decent slope sill window that is reasonable in price, slope sill is the way to go, much more rigid and less mess in the sill.
I faced the same dilemma you did in 1998 - 1953 brick house with old double hungs with storms that had been painted to match the trim -- place looked awful and I did not want to be paining the windows every 7 years and have the heat loss.
I took out everything brick to brick except the interior trim, stop bead, and interior sill/stool. I built a frame - 3 sides - top and left and right - bottom did not get the frame (it was all wrapped in Alum coil stock, caulked well, and where I could I stuffed as much fiberglass insulation in as I could - did not consider foam) as the window needed to sit up a half inch for expansion and the sloping exterior brick sill moved the water away. I used Andersen's -- they were $325 with fake interior muttons and a screen. I could do 2 a day by myself - 39 windows overall.
Mike Smith says a brick to brick window replacement is about $1200 a few years back.
What we got was maintenance free solution, reduced energy bills and immediately, the road noise was negligible - we live on a busy street and that was a real plus. Lastly, we got a house that just looks a lot better than it did -- windows were really beat up and had been painted several times and the painting of the Alum storms was lacking -- We really like our choice. Arguments are strong to keep the old single pane and storms -- I just do not like the look and the recurring maintence.
Arguments are strong to keep the old single pane and storms -- I just do not like the look and the recurring maintence.
Not sure what about the look you don't prefer - sounds like you would have gotten a fairly similar look.
If you are referring to the storm windows, there are "invisible storm windows" available that are, well, essentially invisible - so you don't have to get the traditional wood storm window look.
Regarding maintenance, it would not be unusual for the maintenance on vinyl windows to be as much or more than wood windows. The key is proper maintenance. A properly maintained, painted wood window should last 10 to 15 years between paintings - about the same as the life of a vinyl window. Personally, I think painting is easier than replacing a window.
Part of the problem with wood windows is that people paint them too often, and paint them improperly. The moving surfaces (e.g. margins of the sashes, jambs, etc) should not be painted at all, and the painted surfaces should only need to be painted every 10 to 15 years.