Letters

Edge metal article resounds with reader

Congratulations to Professional Roofing magazine and Lisa McIlvoy, special projects manager for W.P. Hickman, Asheville, N.C., for a well-written article. I subscribe to the notion of the proverbial chain being only as strong as its weakest link. That's probably why "Small components, big effects," November 2008 issue, page 36, spoke so clearly to me.

In her article, McIlvoy provides great background and textbook information about edge metal. As a former instructional designer for a single-ply manufacturer, I've developed methods for what I call "harnessing thought": taking knowledge and conveying it in a manner acceptable and appropriate to an intended audience. I feel McIlvoy accomplished just that.

The industry is just now beginning to leverage Internet technology as a viable means of delivering training. The crew members installing those seemingly miniscule components are the ones who will benefit most from articles such as this, NRCA University's Roofing 101 and other roofing-related online programs.

Just as roof systems depend on even the tiniest components for success, so, too, does the entire roofing industry. The biggest factor in our success will prove to be timely, adequate training.

Ashu Faruki
RoofLogic
Toronto

In defense of cool roofs

I am writing in response to "A matter of opinion," October 2008 issue, page 32, written by Thomas W. Hutchinson, principal of Hutchinson Design Group Ltd., Barrington, Ill.

Hutchinson raises a lot of good points. I could not agree with him more about the need for using two layers of insulation regardless of the type and color of roof system selected. Far too often, we see a certain R-value specified without insistence on two layers of insulation. We see many projects where the two layers specified are value-engineered out to one thick layer. We also share the same concern as Hutchinson with respect to moisture entering roof systems from pouring and curing of concrete flooring.

But with all due respect, Hutchinson's opinion of cool roofing is a bit tainted. Hutchinson should have pointed out he is the paid technical adviser of the EPDM Roofing Association (ERA). Hutchinson talks about cool roofing as though it were new. Reflective roofing has been used successfully for decades. Billions of square feet of certain types of reflective roofing materials have been used in all areas of North America for more than 30 years. With 40 years of experience producing light-colored roofing materials worldwide, we are unaware of the anecdotal side effects of "deflecting the sun's rays" that Hutchinson reports. If there were chronic problems, we would know of them by now.

What Hutchinson fails to mention or have an opinion about is membrane vapor permeability. Vapor permeability will affect the ability of vapor moisture within any roof to evaporate. Not all cool roofs work the same way in this respect.

Actual field studies indicate light-colored PVC roof membranes have a proven track record with no evidence of vapor moisture being a problem. These studies are Field Investigation and Laboratory Testing of Exposed Vinyl Roof Systems, presented at CIB World Building Congress in Toronto in 2004, and Durability of PVC Roofing Membranes—A Field Study After More Than 30 Years of Exposure, presented at the International Conference on Building Envelope Systems and Technology in Sidney in 2004.

Brian Whelan
Sika Sarnafil
Canton, Mass.

Hutchinson responds: I would like to thank Whelan for taking time to read and comment on my article. His confirmation and agreement that two layers of insulation are a best-practices issue highlights my suggestion that the roofing industry needs to come together to achieve mandated changes in the codes and green industry to facilitate more sustainable roof systems.

Additionally, the design community, building owners and facility managers need to be enlightened about the potential increased energy savings that result from two layers of insulation with staggered joints. Double-layered insulation installations with staggered joints also reduce the air flow from the interior to below a roof membrane, which can result in condensation below mechanically fastened roof covers. Both construction-generated moisture and in situ moisture drive need to be considered more often by the design and building communities.

As Whelan points out, I currently serve as ERA's technical consultant, much like the National Research Council Canada served Sika Sarnafil in the Field Investigation and Laboratory Testing of Exposed Vinyl Roof Systems research and paper Whelan references. Had I penned the article on behalf of ERA rather than as an independent architect and roof consultant who has had empirical experience with a number of cool roof projects of concern, I would have indicated that affiliation.

With the promulgation of reflective roof coverings, the concerns associated with them regarding the sun's reflected rays have risen; the concerns are well-documented and making their way through the court system. Congratulations to Sika Sarnafil if it has been able to dodge this mine field.

It is true Sika Sarnafil PVC membranes have what appears to be one of the highest water vapor permeance transmissions of single-ply membranes when tested in accordance with ASTM E96, "Standard Test Methods for Water Vapor Transmission of Materials," at approximately 73.4 F.

Although this permeance may assist in the ability of vapor moisture below a membrane, which may help in some situations, it would not appreciably reduce the potential for condensation and resultant ice from forming on the underside of a membrane in the conditions being observed in Midwest winters: metal roof decks, single-layer insulation and mechanically fastened roof coverings when interior relative humidity levels are greater than the equilibrium relative humidity based on exterior temperatures, generally around 10 F. The permeance is reduced under such temperatures. Many reported and observed concerns are on large warehouse facilities where design and long-term performance are an issue.

I am familiar with the papers and studies Whelan mentions, as well as their authors. The studies reflect a history of sustainable roof system design. The roof systems studied were robust and bore little resemblance to the roof systems with which condensation is a concern (they had vapor retarders, were over office facilities with low interior relative humidities and used multiple layers of insulation with some roof systems being fully adhered—of which the condensation concerns are greatly reduced).

Sika Sarnafil has a reputation for possessing a specific market share and highly knowledgeable technical staff who take the time to design redundant and technically superior roof systems over some other commodity cool roof systems being offered. Shouldn't the entire industry be striving for such excellence? I would suggest to those interested in long-term performance, which is the essence of sustainability, that they take the time to read the papers Whelan notes and see the result of acknowledging the importance of designing all the components of the roof system.

Support for visual monitoring

NRCA associate Executive Director of Technical Services Mark S. Graham generally explicates his concerns with a gem of wisdom essential to successful roof system application. In "Experiences with FM Global guidelines," December 2008 issue, page 20, it was the gem of all tenets of rooftop advice.

My 30 years of experience as an architect, roof system designer and author of specifications for roofing success have indicated without exception that, as Graham states, the only "effective means of ensuring the quality of low-slope roof system application is by the continuous visual monitoring of the application process at the time of roof system installation."

The stress and pressure of applying hot asphalt to keeping a roof dry and building secure to meeting scheduling requirements diverts superintendents' attention from application. My specifications require a superintendent who does not use tools and is restricted to supervision. Even with the best contractors and trained personnel, a constant vigil must be maintained.

Harold Seckinger
Architect
Homosassa, Fla.