Letters

Clarification for Baxter's article

The one thing constant in the roofing industry is change—new product introductions and refinements and adjustments of existing products and systems occur daily. We at G-P Gypsum Corp. appreciate your publication's role in keeping the industry current about these changes.

The articles in your publication by Dick Baxter, president of CRS Inc., Monroe, N.C., always are informative and based on real job observations. In the January article, "Taking a closer look," page 32, Baxter writes about the improvements we made to our glass-mat roof board, Dens-Deck.® Because of the product's unique characteristics, which differ from other roof boards, your readers may want additional clarification regarding the issues Baxter raises.

First, G-P Gypsum markets Dens-Deck, as it has for more than 15 years, with either a silicone or nonsilicone core. Both cores fully meet ASTM C1177, "Standard Specification for Glass Mat Gypsum Substrate for Use as Sheathing," for moisture absorption. Both are patented and perform equally well. The marketplace can be assured that regardless of which core formulation it receives, Dens-Deck always will meet ASTM C1177 requirements and outperform any other roof board available in the widest variety of applications.

Second, Dens-Deck is an ideal product for high sun-load environments. Since its introduction in 1987, Dens-Deck has been installed in all types of climatic conditions—from dry cold to intense heat and humidity. During the course of those 15 years, G-P Gypsum never has encountered a documented case of the product's degradation under any membrane—whether it is black or white—even in high sun-load conditions. In fact, we are so sure Dens-Deck will perform under these conditions that we warrant the board against degradation for the life of the membrane warranty.

Third, Baxter suggests gypsum is susceptible to degradation from calcination when exposed to temperatures common to torching and/or typical asphalt application. Only a small amount of water vapor is released through calcination when these application methods are used. And this has no adverse effect on a roof system's performance because gypsum is naturally rehydrated as soon as temperatures return to ambient levels.

These facts are supported by Dens-Deck's performance for more than 15 years in hundreds of millions of feet of applications. And that is why G-P Gypsum warrants Dens-Deck against degradation caused by exposure to temperatures common to torching and/or typical asphalt applications.

Calcination of gypsum has been pegged as an "evil stepchild." Actually, calcination is the miracle of nature that makes gypsum the best, most fire-retardant product available for protecting commercial buildings. Calcination allows roof systems containing Dens-Deck to achieve the most comprehensive fire ratings in the industry—even at steep slopes. That said, calcination probably should be categorized as a "super hero."

Again, we appreciate everything your publication and, particularly, Baxter do to help roofing professionals stay abreast of our very technical industry. As always, we look forward to your next issue.

Reinhard Schneider
G-P Gypsum Corp.
Atlanta

Following is Baxter's response to the letter:

"Thank you for the clarification and your willingness to investigate ‘potential' problems."

Information about Stevens' membranes

In the article "Do TPOs comply?" February issue, page 84, Mark Graham, NRCA's associate executive director of technical services, included a chart showing the code listings that some TPO manufacturers had attained for their products. In the chart, Graham did not include the ICBO Evaluation Service Inc. (ICBO ES) report Stevens Roofing Systems has had for several years. Stevens Roofing Systems' ICBO ES report number is ER-4193. It is an active report listed under JPS Elastomerics, Stevens Roofing Systems' parent company.

Because this article also served as a topic of discussion during technical presentations at NRCA's annual convention in San Antonio, this same information was missing from the slide that was shown to a large audience of contractors, consultants, manufacturers and other industry professionals.

I hope you will research the subject matter of your articles and seminars more thoroughly in the future so important information used to compare products is not omitted.

Thomas E. Gallivan
Stevens Roofing Systems
Holyoke, Mass.

Following is Graham's response to the letter:

"I collected the information contained in the article regarding TPO membrane manufacturers' evaluation reports through conversations with each TPO manufacturer. In the case of Stevens Roofing Systems, I contacted you on Nov. 2, 2001, to inquire whether your company had any evaluation reports and, if so, the specific evaluation report number(s). You referred me to Peter Bonavita, with whom I spoke the next day, and he only provided me information regarding your National Evaluation Service (NES) Report No. NER-599. Neither you nor Bonavita mentioned your ICBO ES report.

"ICBO ES ER-4193 provides a basis for a code official's acceptance of JPS Elastomerics' Hi-Tuff Hypalon® (CSM) and Hi-Tuff EP (TPO) single-ply roof systems for compliance with the Uniform Building Code, 1994 Edition, subject to the limitations listed in the report.

"NES NER-599, to which the article refers, provides a basis for a code official's acceptance of Stevens' EP (TPO) roof systems for compliance with the Uniform Building Code, 1997 Edition; BOCA National Building Code/1999; Standard Building Code, 1999 Edition; and International Building Code, 2000 Edition, subject to the limitations listed in the report.

"Thank you for providing me and Professional Roofing's readers with corrected information regarding the evaluation reports for Stevens Roofing Systems' TPO membrane products."

ARMA disagrees with ventilation article

We at the Asphalt Roofing Manufacturers Association (ARMA) wish to express our opinion and provide insight regarding the article "What's the value of ventilation?" March issue, page 20.

The article's author, Carl Cash, principal with Simpson, Gumpertz & Heger Inc., Arlington, Mass., presents the results of a computer simulation of many variables to predict the life of shingles. He focuses on the mean temperature (assumed mean over a year) as directly relating to shingle performance. Mean temperature over a year takes into account night, winter and many other conditions that affect the temperature on a roof. Others have found that mean temperature does not accurately indicate rooftop temperature or product performance.

Roofing material performance is related to the highest temperature a material experiences and length of time a material is exposed at these high temperatures. Attic ventilation affects the highest temperature and length of time shingles are exposed to these high temperatures. A lack of ventilation can increase the time shingles experience the highest temperature by hours per day and increase the temperature on the roof by 6 degrees Fahrenheit to 15 degrees Fahrenheit. At peak temperatures on a roof, this range can make a significant difference. [Calculating] mean temperatures does not take into consideration these differences. Shingle performance also is related to granule adhesion, reinforcement strength, color and other factors.

Although Cash has an interesting theory, we suggest that, similar to a lot of computer modeling, his theory does not appropriately consider natural data. It, therefore, discounts an important factor—attic ventilation in the life of a roof system.

Russell K. Snyder
ARMA
Washington, D.C.

Following is Cash's response to the letter:

"Average temperature is a combination of time and temperature, and changing the maximum temperature will change the average. The fact remains that geographic location, color and roof direction have a greater influence on temperature than any degree of ventilation. If it is appropriate to deny warranties because of a lack of ventilation, it would be more appropriate to deny warranties on roof systems installed in southern climates, roof systems that face directions other than north and all dark-colored roof systems."

Reader clarifies FM approval information

NRCA Associate Executive Director of Technical Services Mark Graham's article, "FM Research approves NRCA details," March issue, page 64, is inaccurate or, at best, misleading.

Factory Mutual (FM) Research does not only approve edge details but also manufacturers of those edges. FM Research has confirmed it has approved NRCA details only when fabricated by one NRCA member, Al Melanson Co. Inc., Keene, N.H.

At this time, other contractors fabricating NRCA details are not producing FM Research-approved products any more than if they copied an FM Research-approved product manufactured by our company, Metal-Era Inc., or W.P. Hickman Systems Inc., Solon, Ohio.

There are many edge details that, when properly fabricated, could achieve FM Research approval ratings. Likewise, there are many contractors who have the ability and quality standards to properly fabricate those details. Unfortunately, there are many that do not.

It is for this reason FM Research approves not only the detail but also the manufacturer and conducts regular audits of that manufacturer to ensure the quality level is maintained.

It is good NRCA recognizes the importance of having a tested and quantified edge, and I hope NRCA members will use tested edge metal whether they fabricate it themselves or purchase it from a manufacturer.

However, it should be made clear that simply bending edge metal per NRCA details will not produce an FM-approved product. For Graham to lead anyone to believe otherwise is a disservice to NRCA-contractor members and the roofing industry.

Robert D. LeClare
Metal-Era Inc.
Waukesha, Wis.

Following is Graham's response to the letter:

"Thank you for clarifying what appears to be an inference that can be made after reading my article. You are correct in indicating NRCA's FM Research approval is not a blanket approval for any sheet-metal fabricator to use the detail configurations described in The NRCA Roofing and Waterproofing Manual, Fifth Edition, and represent them to be FM Research-approved.

"In obtaining NRCA's FM Research approval and its similar approval listing from Intertek Testing Services/Warnock Hersey (ITS), Middleton, Wis., NRCA made arrangements with FM and ITS to allow NRCA members to be sublisted under NRCA's approval listings upon NRCA's authorization and meeting FM's and/or ITS' requirements. This type of sublisting arrangement is necessary because NRCA does not intend to fabricate edge metal flashings; NRCA has conducted the research and testing necessary to obtain the approval listings and is offering sublisting opportunities to interested NRCA members.

"The sublisting process involves payment of fees to NRCA and FM and/or ITS and execution of sublisting agreements with the applicable organizations. NRCA requires an initial setup fee and execution of a sublisting agreement between the NRCA member sheet-metal fabricator and NRCA. Then, NRCA authorizes FM and/or ITS to begin their sublisting processes with the sheet-metal fabricator. FM's and ITS' sublisting processes generally require payment of fees, development of factory audit manual reports, inspections of the sheet-metal fabricator's shop, execution of sublisting agreements, use of FM and/or ITS labels on all listed edge metal flashings, and periodic follow-up inspections to ensure continued compliance.

"The fees an NRCA-contractor member pays for obtaining a sublisting under NRCA approval listings typically are substantially lower than the costs the member would incur if it were to go to FM, ITS or another approval agency to obtain a similar listing on its own.

"As of press time, only Al Melanson has completed the sublisting process and is sublisted under NRCA's FM and ITS approval listings. A number of other NRCA-contractor members are in the process of obtaining their sublistings under NRCA's approval listings.

"If other NRCA members are interested in becoming sublisted under NRCA's approval listings, they should contact me at (847) 299-9070, Ext. 211, or mgraham@nrca.net.

"I hope this helps clarify NRCA's FM and ITS approval listings and how they can apply to NRCA members."

Correction: In "The Prop 65 Predicament," March issue, page 8, it incorrectly stated that asphalt has been added to the National Institute for Occupational Safety and Health's list of carcinogens. The article should have stated that some of the chemicals that compose asphalt have been added to the list. Professional Roofing regrets any confusion this may have caused.