we're replacing all of our windows with aluminum now!

No, No, No! I wish I was reading TH when this original post came out. I am not going to personally attack John the original author but I question his understanding of building energy usage. His analysis of amount of material is fine though. I do residential energy effiency and remodeling for a living. The problem I have with the post is partially covered by the last commenter to the original post. The amount of energy that can be saved by new vinyl windows is small. Getting new windows for energy efficiency alone is a HUGE disappointment in actual savings. DON'T EVER DO IT ONLY to save energy unless you have a Super-Insulated house already and you are out of ways to increase efficiency. This means your walls should be R-30 and your roof R-60 (climate dependent) and you have had a knowledgeable professional conduct a blower door test of the building to quantify and locate the air leaks. Windows only lose 10% of a typical houses energy (by air leaks and through the glass combined). If you have old windows that can be closed and storms likewise, you have an effective R-2. If you put in standard Low-E, argon filled double pane replacement windows with a rating of R-3, you just spent hundreds of dollars to increase your insulating value by a pathetic R-1! You will now save maybe $4/year per window. So, depending on whether you did it yourself or not and the cost of the windows, the payback ranges from 20 to 200 years! Even at 20 years that is double or triple the payback on getting better insulation and air tightening done; or getting a higher efficiency heating(cooling) system.

I put in all types of windows, but what I put in and when is case dependent. Try to aim for Super Windows. I have triple pane windows (two low-e coatings and argon gas spaces) that give me R-8! I get nearly triple the insulating values (I know,R-Values aren't a linear relationship though) and the cost wasn't even double the cost. And yes my house was already super-insulated (orig. built in 1920). You CAN NOT GET THEM IN VINYL. Mine are fiberglass that can be painted inside and out for nice color schemes of old victorians. There are other reasons people get windows: looks, lead paint, operability etc. Sometimes vinyl makes sense, but please lets raise the bar more than an increase of R-1 when possible. If you can wait for replacement windows to be able to afford a better model (material and R-valued) you will come out ahead anyway. I have designed houses that all these extra costs in windows and insulation have been paid for by reduced costs by eliminating expensive heating systems. It was more way more efficient for no more money.

Last note: vinyl frames are flimsy, bend and warp easily, expand and contract a ton relative to the glass and the wood/brick opening you are putting them in. Frequently the air-tightness is compromised immediately and you have a drafty window that is sometimes hard to close and lock. The way cheap vinyl replacement windows are usually put in, only a bead of caulk prevents water from rotting out the sill and wall. Sooner or later, that caulk fails (often due to the huge expansion and contraction ratio) and you may not even know your building is rotting away until the problem is huge. Someone tell me how premature rot and mold problems are environmentally sound.

Very interesting, Jeff. Thank you very much for writing that. I learned a few things...

I understand the cost would be the major factor in deciding what materials to use, but my comment is that PVC has such a high environmental "cost", that it shouldn't be used at all. It seems as though it would rarely reach a level of utility where the cost of production is less than the users benefit. Let's stop taking the short cuts and begin with the use of sustainable materials, otherwise it will be a long time before we are really heading in the right direction. It is possible to build a window yourself!

I've had many an inner city apartment where I'd wake up on a cold winter's morning to find small SNOW DRIFTS coming in from window cracks. On windy days the draft could blow out candles on the bed table. Landlords go with the cheapest alternative. Raise the cost bar of cost too far and they leave it like it is. We need to be more empathetic to the poor who have to choose between paying the heating bill, eating, rent, or living on the street.

Your analysis may be applicable to the middle class home under certain circumstances but that is not where my argument was centered.

Incidentally, I replaced all the windows in my home and chose vinyl because it was thousands of dollars cheaper in capital cost than wood or fiberglass. After 8 separate bids and quite a bit of research I became convinced that the quality and methods of window replacement are as important to efficiency as the window design and OEM performance specs. This is consistent seemingly with your statements. However, poor installation can put a structure at risk regardless of what the window is made of.

Please show your references for the thermal coefficient of expansion for fiber glass vs all vinyl windows. I doubt there is the significant difference you infer.

Have a look at the chemistry of polyester resin and organic peroxide manufacture before you conclude that one is so superior to the other.

Finally, I'd like to mention that since the new windows were in (three years ago) our home is more comfortable by far, we no longer have any spiders or beetles (a constant problem wit the old warped and leaky wooden ones) and the therms consumed have been reduced signficantly.

Well, it makes sense that the benefits of changing the windows (and at what price) will depend heavily on the person's budget and on the state of his/her current windows.

The BBC ran an article on PVC windows about a year ago. The highlights of the article.

1. PVC windows have a maximum life of 20 years. Wood can last 100+ if properly maintained.

2. The cost both financial and ecological for replacement PVC windows is far higher than the exist wood single pane windows.

Like Jeff said. If your existing wood windows are in good shape then don't replace them.

Very interesting info. I had Home Depot come out two months ago and give me an estimate for vinyl replacements. it came in above my budget but now i need to consider if i even need to do my windows. the house is 35 years old with single pane glass and storm windows. They aren't too bad but aren't the best either.

Don't trust everything you read in the newspaper, even if it is BBC! The number for design life cited (20 years) is flat wrong. My own home has 35 year old vinyl siding and showing no signs at all of failure -- it was properly mounted of course. Ofttimes people confuse warranty with design life and these are very very different. A reasonable design life estimate for a vinyl window would be 60 year plus.

Joe, you might want to consider interior storm windows for your home. Several places sell them online, or you can make your own with some ingenuity.

For homes with single pane windows, this can make a big difference in energy use for a lot less than paying to replace them. And many people can't replace their single pane windows without getting in trouble with the historical society...

We had our original wood windows "repaired" a few year back. We have an older home, and keeping the look of the original windows was important to us.

We went with a company that comes in and (a) removes the glass from your window and replaces it with double pane insulated glass. You lose the outside wood on the cross-hatching (but they match the style and stick new wood on the outside of the glass), but the inside is the original cross-hatch wood, (b) they remove the counter-weight and fill that area with insulation, (c) replace the window lock and put new rubber insulation where the windows meet up and meet the frame, etc.

They did a really nice job, and we were happy to keep most of our original window.

Since it is technically a "repair" and not a "replacement", they do not have to charge sales tax... at least, not in our state.

Okay, if you are getting snow drifts inside, obviously storm windows do not exist (or don't close) and the window sash leaks alot. In that case there is a much bigger opportunity to save money and add to comfort and new windows are warranted. Next comes the cost decision of upgrading or not. I work on lots of historical homes that I would never put vinyl in for aesthetic reasons alone. Some homeowners are determined to get new windows and often can only afford vinyl. If I think this is better than not doing it at all then I swallow hard and at least ensure they are installed well, as far as long term water-tightness and insulating/airsealing the jamb. See this water leak study:
www.jlconline.com/jlcupdate/2003/0311/3.html

By the way, I have done blower door tests on houses that only got new windows (that I put in ,very well sealed even) where the total building air leakage was reduced by very little (3%). Imagine if they were installed in a typically slapdash fashion. Occasionally, I see bigger improvements but that is when the windows have no storms and are in horrendous shape.

The calculus is different with rental property. Many owners will only do the cheapest or nothing at all. If I am a tenant, I at least put plastic on the windows to keep the snow and breeze out! Or I don't move there at all if I am paying the heat bill. This discussion hardly applies to landlords that don't pay for heat, since 99% will never make a business decision based on environmental concerns due to vinyl production. Housing authorities and public entities are different and have been known to put in fiberglass windows since they know they will own the property for many years and will have to contend with the short life expectancy (operational durability) of vinyl. I can sometimes sell landlords on the durability of fiberglass.

As for the performance of different materials, fiberglass window frame makers do it because they know their product is superior, otherwise they would not fight an uphill battle. I rely on the US Green Building Council's reports and some literature from various fiberglass companies. Check out this link, I assume the info is reasonably believable since it jives with other sources I have seen: www.inlinefiberglass.com/whyfiberglass.htm

In any case, purchasing windows should be part of a larger energy strategy for any building and is rarely the first thing that should be done. Once you get to the point where you have done everything else possible to a building, the windows are a small problem (10% on average) that I urge people to live with a bit longer in order to save enough extra money to do the right thing.

I work for a company that makes and sells vinyl-clad conservatories and skylights. They feature windows framed entirely in vinyl. We do not guarantee them beyond 10 years, because it is not expected to last over 20. We also sell hardwood conservatories, and confidently tell our customers that the hardwood will outlast the vinyl several times over.

Beyond the nastiness of vinyl manufacturing, I would never buy vinyl for my house, because it's quite simply crap quality. The look and feel of NEW vinyl windows can't hold a candle to timber or metal. I can't imagine how bad it gets as the plastic sags and gets brittle from sun exposure. It also cracks and splits like crazy. We are contantly having to replace parts that are broken during installation. Salesmen won't tell you that when you buy it.

Which is better, aluminum or vinyl? Or some combination?
http://www.rooflanterns.com/