I appreciate your comment and I understand that this is complex and not a black and white issue. In your opinion would 1 point of u factor improvement be a substantial change?

As far as it applies to how we charge for it, it is a very worthwhile option and great bang for the buck in terms of an efficiency upgrade.

Any improvement in performance is worthwhile at the right price. Is a 1 point improvement worth $100 per window? Probably not if all else is equal, but foam filling is generally reasonably priced. Wow is right on in characterizing it as good bang for the buck to gain a point or two

I definitely endorse foam filled frames for a few reasons. first off, it insulates your frame. Even though most windows are multi chambered which do provide a little insulation, foam filling really does a great job at preventing heat transfer through the frame. Foam also adds some structural integrity as well.

For these reasons alone, along with making a window more energy efficient, i will always choose a window with foam.

Of course someone selling a brand that doesnt offer foam will tell you its a gimmick but thats simply a lie. in fact Foam can increase your energy performance by 1-2 points. This is especially important since energy star is revising their criteria for energy star ratings next year. A window will have to have a Ufactor of at least .28 or ,27 ( i forget which).

Foam works.

A difference of .01 or .02 in U factor is negligible. The energy savings per year would be pennies per window, not dollars. Until these windows are tested after a year, after 5 years, after 10 years of operation in real world conditions, the numbers are pretty worthless. Here's a good calculator where you can compare energy use using different u values. Just total up your window area and use that as your "greenhouse" area.

http://www.littlegreenhouse.com/heat-calc.shtml

Ksc36

You are very misinformed and that website is ridiculous.

A solid window that is engineered and designed well will maintain its performance for years, a cheaply made window will not. In fact, a cheaply designed window may he somewhat energy efficient for a while but eventually any performance rendered will be diminished over a rather short period of time.

Do you have anything to back up that propaganda or is that the salesman BS coming out? Remember, you are arguing about windows with an R value of 3.33 (u- .30) vs 3.57 (u- .28), or an r- .24 difference. Yes point 24. That's about equal to a coat of paint...

Ksc

Its always guys like you that hurt the industry by purposely steering your customers to cheap products your building supplier stocks rather than using the most energy efficient products. I know the drill, push the cheap stuff so you have a much better chance at getting the job and lie to your customers about the benefits of the better products.

The discussion here isn't cheap products, it's the benefits of negligible decreases in u value for an additional charge based on mythical energy savings. I can see why a low level window salesman would find the energy calculator "ridiculous", as it goes against all his training at Grifter University. I don't need to lie to anyone as the numbers don't lie, only window salesman do.

On the subject of insulation, I haven't seen it used in fiberglass window frames I've been researching, is there a reason for that?

Interesting conversation, and some valid points ksc. There are a few things that I think should be pointed out on this topic:

-I don't believe that anyone has stated that one or two points of u factor will save a boatload of money on energy. In fact, u factor is only one component that should be looked at. SHGC is very important as well, as is air leakage. I only looked at that calulator briefly, but I'm not sure how accurate it can be without taking SHGC into consideration, as it is would be in residential heat loss calculations. I did not see anywhere that it takes shgc into account.

-Cumulative improvements in multiple areas (IE: u factor, etc) can add up to have a more substantial effect. Couple points of u factor here, better shgc, tighter assembly over a houseful of windows can and does make a difference.

-Condensation resistance is another issue that can be affected by a very small change in u factor.

-There is no evidence to suggest that there would be any substantial decrease in the thermal performance of a quality window over time. Perhaps you could provide some sort of evidence to back up a statement implying otherwise? To say that these ratings are "worthless" is a pretty strong statement, and goes against all logic.

-In addition to a few points of u factor mitigating energy loss, performance ratings often go hand in hand with product quality, particularly when it comes to vinyl windows. Looking at a product that gets a very average .30 u factor for instance vs one that achieves say a .26 will often indicate a superior product. When one examines the other ratings such as shgc, ai, dp, vt, etc, this will generally be confirmed as such. High quality windows generally perform well in all of those areas.

Back to the original question, and MOST IMPORTANTLY, whether it is foam filling or any other product option, there should be a cost vs benefit analysis done to determine whether it is a worthwhile option. Anyone that says foam filling should be chosen at any cost probably has some nefarious motivation, as does someone that says it shouldn't. In fact, this whole conversation can actually probably go right into the debate of whether it is a wise investment to even replace windows at all, to which the answer is "it depends". If you expect them to pay for themselves in energy savings, the answer for most folks is no. That said, once you consider the added property value (most reports put ROI in the 60%+ range), comfort, quality of life (easy cleaning, attractiveness, etc), it can actually be a pretty worthwhile investment, particularly if other areas of the home like attic insulation and air sealing have already been taken care of. The real question is, what is the motivation for this attack?

Christine Anne,

Fiberglass isn't used in window frames (as an insulation option) because it is pretty much worthless. Foam will have a higher R-Value per inch (as installed) and is much easier to get in an uniform manner that will work as intended.

+1 to HomeSealed's comments.

I don't see where anyone was claiming it was going to save big dollars.

At the end of the day, you want to get the most efficient window that you can afford and fits your design criteria. Foam in the frames is a nice option (if it is part of the window design) because it helps thermally break the frame/sash from the exterior and usually raises the CR (Condensation Resistance) number in the process. The closer the surface temp of the window can be to the interior temps, the less likely you are to form condensation.

ksc36,

You can't look at the U-Factor comparison (and conversion to R-Value) as a linear relationship. What you need to look at is the reduction of weak points in the wall assembly.

Example:
If you have a 2x6 wall (assuming R-19 nominal and not factoring in the framing r-value) and look at the impact on average R-Value of the wall between two windows, it can be more stark than you think.

Lets assume 75% walls and 25% windows for an average home.

Average R-Value of the total wall with a windows of a U-Factor of 0.30 = 8.74
Average R-Value of the total wall with a windows of a U-Factor of 0.27 = 9.35

Total impact on average R-Value (Total wall with windows and walls) = 7% improvement.

Nothing to shake a stick at.

I think she was asking why foam insulation is not used in FG windows, not why FG insulation is not used in vinyl windows... :D

To answer, it probably does not offer a substantial improvement in performance, at least not enough where the manufacturers think that they will be able to sell it effectively and still make a profit.

"I think she was asking why foam insulation is not used in FG windows, not why FG insulation is not used in vinyl windows... :D

To answer, it probably does not offer a substantial improvement in performance, at least not enough where the manufacturers think that they will be able to sell it effectively and still make a profit."

Yes, sorry for the confusion. Thanks HomeSealed.

That's what I meant (i.e. fiberglass insulation in frames) in my post above.

It doesn't work because it can't be installed as it should be (i.e. non-compressed, full fill).

Thanks WoW, now I understand what you meant.

If the frames are fusion welded, wouldn't it melt the foam during the process.

“If the frames are fusion welded, wouldn't it melt the foam during the process.”

definiely NOT !

The foam does melt where it contacts the welding iron, but only where it touches the iron as as the sections are brought together. This does not impact the R-Value of the foam anywhere else.