Letters

Comments about fire testing

I read "Report on fire testing" by Mark Graham, NRCA's associate executive director of technical services, in the March issue, page 24.

I have a few clarifications and comments.

The October 2001 fire testing commissioned by the Midwest Roofing Contractors Association (MRCA) included the following roof systems: built-up, modified bitumen with granulated cap sheet, PVC, TPO and EPDM. All PVC roof systems tested passed the spread-of-flame testing of less than 6 feet to achieve a Class A-rated system. The other roof systems were constructed using the same test, test equipment and test personnel, and more than 50 percent of the systems tested failed.

Based on the 2001 test results, MRCA determined there was no need to further test PVC and modified bitumen roof systems.

The idea of testing new and aged (exposed) roof systems and verifying the fire performance and change in fire performance is to be applauded. Roofing contractors are in the undesirable position of installing roof systems that meet building codes. They rely on manufacturers to produce products that meet building codes. Fire performance of a roof is a life and safety issue first and foremost and, secondarily, a factor in property protection.

The fire performance of all roof systems (membranes and insulation) changes with typical rooftop exposure. Basically, products that require fire-retardant additives to pass initial testing will lose some of their fire resistances over time. It also is expected that products with surfacing (mineral granules) require maintenance to maintain their fire ratings. Some roof systems, such as PVC, are inherently fire-resistant and actually can improve over time.

Maybe the test is flawed, but some systems passed and others did not. If the test is flawed, it should be fixed fast.

As stated previously, PVC roof systems passed the original testing. There is no evidence that a noncombustible cover board is needed for mechanically attached PVC roof systems. We request NRCA and Graham recognize a noncombustible cover board is not needed for all mechanically attached single-ply roof systems.

In my company's experience, a noncombustible cover board will reduce the effect of the insulation substrate. It may do little to affect the spread of flame on the actual single-ply membrane. Are MRCA and NRCA concerned about the insulation or membrane?

Brian J. Whelan
Sarnafil Inc.
Canton, Mass.

Following is Graham's response:

I thank Whelan for taking the time to share his thoughts and concerns with me and the readers of Professional Roofing.

My column provides a brief summary of the joint MRCA/NRCA report, "Fire Testing of Membrane Roof Systems," that was issued to January. Although the column appears under my name, the report and its conclusions and recommendations are that of MRCA and NRCA.

In his letter, Whelan raises questions regarding the report's recommendation for the use of cover boards. On this topic, there are several relevant points.

During MRCA's early fire testing, it discovered the presence of a suitable cover board had an effect on exterior fire performance of many single-ply membrane roof systems. In several instances, similar single-ply membrane roof systems were tested with and without noncombustible cover boards and the roof systems with the cover boards exhibited significantly better fire performance. Before this finding, MRCA and NRCA were not aware of the extent of the role cover boards had in exterior fire performance testing.

Since 1988, NRCA has recommended the use of cover boards over polyisocyanurate, polyurethane and phenolic rigid board insulation where hot-applied bituminous membranes are installed. In 2000, with the publication of NRCA Technical Bulletin 2000-3, "Use of cover boards over polyisocyanurate roof insulation," NRCA expanded its earlier recommendation to include recommending the use of suitable cover boards as a part of all low-slope membrane roof assemblies, including thermoset and thermoplastic single-ply membrane roof assemblies in ballasted, mechanically attached and fully adhered configurations.

In a letter NRCA received from Underwriters Laboratories (UL) Inc. while MRCA and NRCA were developing the report, UL indicates, "It's been our experience that Classified systems using appropriate cover boards typically yield better external fire performance than those systems without a cover board."

Based on these points, MRCA and NRCA made the recommendation included in the report that designers should include suitable noncombustible cover boards in their designs for all newly installed mechanically attached single-ply roof assemblies. Both MRCA and NRCA stand by the recommendations contained in the report.

In considering the recommendations contained in the report, it should be realized UL listings or FM approvals are specific requirements intended to achieve minimum fire-resistance requirements as prescribed by building codes. The recommendations contained in the MRCA/NRCA report are guidelines that likely are more conservative than the codes' minimum requirements.

Concern about energy efficiency

As the immediate past chairman of ASHRAE 90.1 "Energy Standard for Buildings Except Low-Rise Residential Buildings," and an independent consulting engineer, please allow me to offer some comments about "Saving energy with the right roofs," February issue, page 34.

The article makes it appear tax deductions for improved roofing under the new 2005 Energy Policy Act can be attractive. The act has provisions for federal tax deductions of up to $1.80 per square foot when the energy cost, not consumption, is reduced by 50 percent or more when compared with meeting the requirements of ASHRAE 90.1-2001. Although improved roofing certainly can result in lower energy use, the benchmark for the tax deductions is ASHRAE 90.1, so roof system performance must substantially exceed the benchmark to qualify. Exceeding the benchmark may not be technically or economically feasible even with tax deductions.

The cost per additional inch of insulation is the same as the initial inches, but the energy saved follows the law of diminishing returns. Greater insulation thickness can mean more space, detailing and fastening issues.

The ASHRAE 90.1 provisions for cool roofs only apply in the warmest climates, and then, they simply allow lesser amounts of insulation. Moreover, with higher levels of insulation, the benefits of cool roofing are correspondingly diminished. And the energy act does not "reaffirm the validity of various research findings related to energy efficiency of roof systems." In addition, the article should have made it clear the energy act provides tax deductions, not tax credits, and to the extent that deductions are taken, comparable reductions in the tax basis for the building must be made. Finally, compliance with ASHRAE 90.1 is not required by the International Energy Conservation Code; it is simply one option, and that option rarely is used.

Giving the impression that more insulation in roofs always saves energy is not technically correct: There are some commercial and industrial applications where more roof insulation increases energy consumption. This occurs in buildings with long hours of operation and higher than usual internal heat gains from people and equipment. During the many mild-temperature hours, more insulation traps the internally generated heat in the building, requiring more cooling energy than less insulation, which would have allowed that heat to escape. Little or no heat must be bought in these buildings, because the internally generated heat is all that is needed for comfort.

I hope the SpecRight program will provide technically correct results for all applications in all locations. If the results in the article are any indication, more work is necessary before NRCA can responsibly promote the program. In addition, using the same insulation levels throughout an entire building is not always in the best interest of the building owner. For example, the roof in a nonair-conditioned gymnasium in an air-conditioned school should not have the same insulation as in the rest of the building. Roofing contractors and consultants do not need any more reasons for disputes when their energy analyses fail to match reality.

Lawrence G. Spielvogel, P.E.
Lawrence G. Spielvogel Inc.
King of Prussia, Pa.

Following is Professional Roofing's response to the article:

The SpecRight Program is intended to inform building owners about the complexities of roof system design, and NRCA certainly agrees proper roof system design involves more than just adding insulation. For more information about the SpecRight Program, log on to www.specright.net.

COMMENTS

Be the first to comment. Please log in to leave a comment.