Questions about venting base sheets
In response to Helene Hardy Pierce's (Wayne, N.J.-based GAF Materials Corp.'s director of contractor services) article "Speaking up for venting base sheets," November 2002 issue, page 30, I am confused.
Is Pierce referring to GAF's Stratavent® Eliminator,™ a perforated base sheet that uses hot asphalt to flow through holes to adhere it to the polyisocyanurate board, or a base sheet that is mechanically fastened or spot-mopped?
If it is a perforated base sheet, shouldn't close attention be given to the facer used on the polyisocyanurate because the asphalt that flows through the facer and adheres to polyisocyanurate would be the weakest link during high winds?
When using a perforated base sheet, would this application pass FM Global's calorimeter test for interior fire? In my opinion, it would not.
When a perforated base sheet is applied and must precede the hot asphalt, is it possible to apply when wind is blowing at 10 mph to 15 mph? Would it be possible to apply the perforated base sheet far ahead of the hot asphalt application?
If the perforated base sheet were not adhered, would a roofing worker's sticky shoes or mechanical equipment with sticky tires adversely affect the application of the finished built-up roof system?
I don't mean to shoot holes in Pierce's article (no pun intended), but I would appreciate answers to my questions.
Ridgefield Park, N.J.
Following is Pierce's reply to the letter:
"Thank you for your letter.
"I was not referring to a specific base sheet and, in fact, described several application methods. The appropriate application method depends on the type of venting base sheet, substrate and roof system being installed, as well as a manufacturer's recommendations regarding the use of its base sheet.
"Regarding your questions about perforated venting base sheets, wind-uplift resistance and calorimeter testing have proved inferences of inferior wind and fire performance completely are unfounded. A quick perusal of FM Global's Approval Guide will confirm this, which is contrary to your opinion.
"The application of any roof system in windy conditions presents the need to take precautions, and a product's manufacturer should be consulted for recommendations. The most recent guidelines for the installation of Stratavent Eliminator Perforated Base Sheet can be found in GAF's Contractor Services Technical Bulletin C-78.
"Roofing professionals should investigate the applicability and suitability of all options available to them."
Comments about ventilation
I would like to comment on "What is energy-efficient?" December 2002 issue, page 24. The overview and points Mike DuCharme, EPDM marketing manager for Carlisle SynTec Inc., Carlisle, Pa., made are valid; however, they only apply to non-vented low-slope roof assemblies.
As a manufacturer of steep-slope metal roof systems, we are struggling to get out our message that most steep-slope roof systems are used with vented attics. If an assembly is ventilated properly, any heat that is not reflected or emitted and migrates into the attic is released, which provides for efficient energy use in the building.
The three model building codes still in use in the United States do not mandate the use of ventilation and leave the issue to the discretion of local building officials. The new International Building Code includes requirements for ventilation of attics and cathedral ceiling assemblies for steep-slope roof systems.
Once ventilation standards become adopted as they have been in Canada for many years, roof coverings will last longer; homes will be more comfortable and energy-efficient; and the benefits of higher reflectivity and emissivity of a roof covering will be minimal.
As an industry, I believe we need to direct our efforts to promote the benefits of ventilating steep-slope roof systems, especially with the recent liability regarding mold issues.
Dura-loc Roofing Systems Ltd. and American Roofing Industries Corp.
Courtland, Ontario, Canada, and Antioch, Calif.