Column Poses Questions about What is “Warm-Edge”
As always, I look forward to reading Door and Window Maker! I do have a comment on the article, “What Puts The ‘Warm’ Into Warm-Edge? (see January-February DWM, page 12).
There are some questions to be asked that effect how to use and interpret the excellent data.
1. The list did not include the INEX spacer. It did not specify which type of Super Spacer was used—high or low profile, silicon based or other material. It also did not include thermally broken acrylic spacers. I assume it did not include the higher performing Vilda steel alloy material used in a new product from GED or other steel spacers.
2. I don’t personally have the expertise to say that how the spacers were used in regard to choice of, amount of and location of sealants for each spacer type is what is recommended by each spacer manufacturer. Some of this data was actually included with the chart which is commendable, even if it did not go far enough to assure me that each manufacturer had the opportunity to specify how their product would be
3. The article ignores other aspects of field performance and manufacturability that could effect spacer performance. To many manufacturers, a difference of U factor from .34 to .304 may not justify these other factors.
In Canada, we have a system that can directly be translated into expense on heating costs. It is called an Energy Rating. I believe this was also developed by Enermodal, the same company that did Richard Warren’s testing.
I am told that a difference of .05 U factor changes the energy rating of a window by 6.2 points. Now, a difference of 1 point per square foot on an ER rating may save approximately $.04 (U.S. dollars) a year for the homeowner. (This varies depending on many factors including geographic location, type of heating fuel and the condition of the heating system, so I am taking a cost that could reflect a decent system in a northern environment.) The above difference from the best to worst spacer in one category was .036U so, it would have a difference of 4.464ER and be worth $.22 a year per square foot of window.
If a reasonable home has as much as 200 square feet of windows then the potential savings on fuel between spacer could be about $45 dollars a year. This is, however going from aluminum to the best-rated spacer on the chart.
If you compare Intercept as the bottom warm edge on the chart, the difference is only .019 U factor using the same approach as above, the difference in potential savings is about $19 in the colder climates.
On that basis, I believe that issues of durability in the field and manufacturability that effects cost and quality should never be ignored when evaluating choice of spacer by a manufacturer.
vice president of marketing
Vinyl Window Designs Ltd.
Clarifying Column Critiques
Editor’s Note: DWM asked column author Richard Warren to respond to the above letter.
Lewin makes some good points regarding the article. To clarify some of his questions, please note the following:
Examples included in the article are based on spacers broadly used in the industry, particularly those that, at a minimum, pass North American certification standards. TruSeal searched certified product listings from both the Insulating Glass Certification Council (IGCC) and the Insulating Glass Manufacturers Association of Canada (now the Insulating Glass Manufacturers Association) and was unable to locate listings for either INEX spacers or Intercept spacers using Vilda stainless steel. The IGCC Certified Products Directory, dated August 2003, did not include references to INEX (Plastic Spacer–PL) being certified by any parties. In addition, this directory does not include separate listings for the Vilda steel Intercept construction.
In regard to Super Spacer, we used the silicone foam version for the modeling and would agree that if the thinner profile were used it would make some difference.
Our company supports any manufacturer’s choice to pick the most efficient spacer system for their operation and agrees that some compromise in effective U-value is acceptable. However, many state codes, as well as Canadian energy codes, determine acceptability via maximum U-values (or minimum ER). In many cases a change of 0.01 U-value can determine whether a window meets code or not. Most manufacturers are looking for options to meet these requirements while also producing windows cost effectively and efficiently to maintain their competitive advantage. It seems probable that, over time, these standards are going to become more aggressive and that adoption will increase as consumer awareness increases.
In regard to the real cost of energy and its relationship to U-value, we went to the Efficient Windows Collaborative website (www.efficientwindows.org) and modeled a typical home in Buffalo, N.Y. — a typical cold climate site. The cost savings of a U-value change from 0.49 to 0.36 with comparable solar heat gain coefficients was approximately $80 per year for the home. This may be greater than the 0.05 difference, but the savings seem significant enough to justify some interest by consumers. We do agree that realizing savings relative to production efficiencies and costs is a delicate balance, but everyone wants first to be able to sell a
window. Providing energy efficient products allows TruSeal to differentiate itself in the marketplace.
technical services representative
TruSeal Technologies Inc.
Look at Glazing Choices
In the recent issue of DWM, I was disappointed to see that Mr. Fitch’s article of “Improving Efficiency Through Glazing Choices” (see March Door & Window Maker, page 12) turned out to be a self-motivated push for ISRU’s (which I believe his company has a connection with) and not a proper article dealing with glazing choices for the window and door market. He pushed his product and slammed the silicone market at the same time. He didn’t deal with tapes or other options available to the window and door market. Fitch should do more homework on glazing choices and then take out an ad like all of the other sealant firms and pay for it instead of abusing his privilege of writing an article in a major publication. He should be made to re-do it but with ALL of the facts presented this time.
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