RCap Plus utilizes ground and packed granules, and these granules ensure more coverage in the membrane per square. Malarkey grinds the asphalt granules at its South Gate, Calif., manufacturing facility.
The solar reflectivity and limited heat absorption of the RCap Plus cap sheet are key design features of the product. RCap Plus meets CEC Title 24, Part 6 standards and has an initial Solar Reflectance Index (SRI) rating of 87. As part of a roof system, RCap Plus may help decrease energy costs used to cool the building and extend roof service life.
Whether you’re re-roofing a historic building that needs to maintain its aesthetics or you’re working on a new roof construction that has to make a statement, there are many instances in which a building owner would want his or her roof to generate a specific architectural appeal. The most difficult part of this is balancing durability and beauty with cost. Roof systems today have evolved to solve this conundrum. Now, copper and silver synthetic PVC membranes are being used to achieve the desired appearance of a metal standing-seam roof at a fraction of the cost without sacrificing performance.
Alternatives to Metal Roof Systems
Copper and silver synthetic membranes are great cost-effective alternatives to metal roofs. As flexible synthetic systems, these roof membranes are economical and easy to install by conforming to complex geometries.
Certain synthetic PVC roof membranes on the market today are offered in a variety of colors, some of which can mimic the look of metal roofing. While these roof membranes offer the proven long-term performance of flexible polyvinyl chloride (PVC), they provide the metal appearance via the addition of pigments that can chalk or fade as the pigmented membrane ages, therefore losing the desired aesthetic feature.
Conversely, SOPREMA SENTINEL Copper and Silver Art PVC membranes incorporate copper or aluminum metallic powder into the PVC formulation, producing an enhanced metallic look. Unlike pigmented membranes, SENTINEL Copper Art provides the same weathering capabilities as traditional standing seam copper—the SENTINEL Copper Art will patina as a traditional copper roof would. Silver Art is unique because the color will not fade due to the addition of metallic powder, and its surface layer is factory embedded with an acrylic shield treatment to resist dirt pickup and chalking. Copper Art and Silver Art membranes provide the long-lasting aesthetic appearance and waterproofing abilities of a metal roof.
Applications for Copper and Silver Membranes
Copper and silver roof membranes are often used on buildings where aesthetics are important. Historic buildings, churches, schools, government buildings and army bases are a few examples of where this type of roof membrane has been installed. These buildings may require a particular appearance or designers may simply wish to update the appearance or provide some panache. Mansards or other areas of visible existing light-gauge metal roof systems may be present on these buildings and flexible copper and silver roof membranes may be used as an alternative aesthetic solution.For example, since 2007, the slate roof of the Snyder-Phillips residence hall at Michigan State University had been leaking. The university needed to replace the existing slate roofing system with a new system that would meet the aesthetic requirements of the historic building. SOPREMA SENTINEL Copper Art was installed as a cap sheet to provide the desired appearance and the required long-term performance.
In addition, the Glenside Public Library had an existing standing-seam roof that was tied-in to a low-slope ethylene propylene diene monomer (EPDM) roof. The tie-in between the two materials was problematic and continuously leaked. The library wanted to preserve the standing-seam appearance, but the noise created by wind and rain on the metal roof was a concern.
SOPREMA SENTINEL Silver Art was selected because it could provide the desired look while eliminating the tie-in issues between the steep- and low-slope roofing materials. SENTINEL Silver Art met the library’s leak-free and architectural needs, plus the roofing contractor liked that the SENTINEL membrane was easy to install and looked great upon completion. In addition to its aesthetic appeal, SENTINEL Silver Art also offered the benefit of significant noise reduction when compared to the former metal roof system.
Roofing Technology Advancements
As roofing technology advances, the options for creating a desired aesthetic have evolved. SENTINEL PVC Copper and Silver Art are high-performance roof membranes that provide the appearance of metal with the flexible, long-term performance of PVC, without the weight, expense or complexity of a traditional metal roof.
I have a water phobia. When I was very young I fell into a pool and nearly drowned. Consequently, I never learned to swim out of sheer fear. Despite my attempts to avoid it, water continues to haunt me. (See an article I wrote about my Chicago condo’s construction defects for some background.) It’s ironic I now live along the nation’s southernmost glacial lake. I love the view from our home, but the lake’s recreational opportunities are lost on me.
To further substantiate my negative feelings toward water, 2015 was an especially wet year for the Midwest. In mid-December, my Iowa town received 5 inches of rain in a day and a half. Our basement—where my office is located—flooded (for the second time since August). My husband bought the house (which he planned to make his lifelong bachelor pad) knowing the basement might leak during heavy-rain events. He never planned to have anything down there. Then I came along.
As this issue was coming together—around the same time our basement was soaked—I read a line in “Tech Point” that really resonated with me: “… water is construction’s worst enemy, so when it goes where it shouldn’t, it’s causing damage—seen or unseen.” I shared that line, which was written by Armand T. Christopher Jr., AIA, with my husband. The next week we hired a basement waterproofing contractor to solve our ongoing water problems.
Christopher’s story likely will resonate with you, as well. He and his team had recently installed a PVC roof system on a high-profile government building in central New Jersey. Six months after the install, a three-day nor’easter exposed numerous leaks in the building, which the client thought were coming from the new roof. The ensuing “detective work” Christopher’s team completed was tedious but uncovered the cause of the leaks and made Christopher and his colleagues heroes.
Christopher points out a nice feature of the roof’s thermoplastic cap sheet is areas where water had pooled within the roof system were dried and resealed with heat-welded target patches. Thomas W. Hutchinson, AIA, FRCI, RRC, CSI, RRP, builds upon this idea in his “From the Hutchinson Files” article. Hutchinson notes today’s “new age” roofs may not require removing all system components during reroofing. Instead, it may be in the customer’s best interest to consider restoration; roof-cover removal, enhanced with additional insulation; using the existing roof membrane as a vapor retarder; or membrane removal before installation of a new roof cover.
My husband and I seem to have found the best solution to our basement water problems. Although we’re not looking forward to the construction ahead, we are excited about all the things we can do with a dry basement. Right now, we’re envisioning a mini spa in which we can relax after a stressful workday—another welcome upgrade my husband never imagined for his “bachelor pad”.
I responded by immediately going to the building. I was accompanied by the roofing system manufacturer. As the client led us around the building, water was dripping through suspended ceilings all over, which gave us the sinking (almost apocalyptic) feeling you hope to never know. However, when we went up to examine the roof, much to our surprise, there was no blow off; no seams torn; in fact, no apparent defects at all. Our thermoplastic cap sheet looked perfect on the surface.
What we did find, however, was large amounts of water trapped between this cap sheet and the 90-mil bituminous base sheet underneath. This was creating large water-filled blisters on the roof that looked like an old waterbed as you walked up to and around them. No matter how hard we looked we just couldn’t find defects in the membrane surface or at any of the flashing connections or terminations that could be causing this. There was, however, a likely suspect looming adjacent to and above our roofs. The building experiencing the roof leaks has one whole face that is an aluminum-framed glass curtainwall. It extends up above the roof lines, slopes up (from the vertical) forming a peaked skylight, which then slopes back toward these roofs that were holding water. On the upper roof, sawtoothed skylights of the same construction were dripping water when we first arrived. This gave the only clue to where the “smoking gun” may lie.
Water was dripping from the saw- toothed skylights into a planter in the 4-story atrium. The client said that was typical with all hard rains. Armed with this clue, and no other apparent explanation for such a large amount of water intrusion, the owner engaged us to find out what indeed was the root cause of this problem.In a couple days, the dripping subsided and most of the water blisters had dissipated or at least were reduced and stabilized. In the interim, I assembled a team consisting of a roofing restoration contractor (this is not a rip and tear production contractor but one especially geared to finding problems and making associated repairs), skylight restoration contractor and testing agency capable of building spray racks onsite to deliver water wherever it’s needed. With this team, I embarked on a systematic investigation that would make any “detective” proud.
First, we plugged the roof drains and let water pool on the roof until the en- tire surface was wet. Meanwhile, “spot-ters” inside the building were looking for any sign of water intrusion using lights above the dropped ceilings. When this showed nothing, we began constructing spray racks and running water for set intervals on every adjacent surface rising above and surrounding the lowest roof in question. We first sprayed the exposed base flashings, then rose up to the counterflashing, then further up the wall, then to the sill of the windows above, etc. Then we would move laterally to a new position and start again.
This proved painstakingly tedious, but we knew that making the building leak was not enough; we had to move slowly and systematically to be able to isolate the location to determine what exactly was leaking and why. It is important when applying water this way to start low and only after a set period move upward, so when water does evidence itself as a leak, you know from what elevation it came.
After an entire day of spraying the rising walls surrounding the first (low) roof area, we could not replicate a leak. Somewhat frustrated—and rapidly burning the testing budget—we began the second day focusing on the adjacent peaked skylight, which is more than 75- feet long.Again, we started low, where our base flashing tied into the knee-wall at the base of the skylight, below the aluminum-framed sill. Still no leaks. Late in the day, when we were finally up to the glass level, we sprayed water from the ridge and let it run right down the glass onto our roof below. Finally, we found some leaking occurring at a skylight flashing to wall connection. OK, that was reasonable to anticipate and easy to correct.
For nearly two years in this magazine, I have been discussing the various components that make up a roof system: roof deck, substrate boards, vapor/air retarder, insulation and cover boards (see “More from Hutch”, page 3). Although each component delivers its own unique benefit to the system, they are intended to work together. When designing a roofing system, components cannot be evaluated solely on their own and consideration must be taken for a holistic view of the system; all components must work together synergistically for sustainable performance. Unfortunately, I often have seen that when components are not designed to work within the system unintended consequences occur, such as a premature roof system failure. A roof system’s strength is only as good as its weakest link. The roof cover is the last component in the design of a durable, sustainable roof system—defined previously as being of long-term performance, which is the essence of sustainability.The roof cover for this article is defined as the waterproofing membrane outboard of the roof deck and all other roof-system components. It protects the system components from the effects of climate, rooftop use, foot traffic, bird and insect infestation, and animal husbandry. Without it, there is no roof, no protection and no safety. When mankind moved from cave dwellings to the open, the first thing early humans learned to construct was basic roof-cover protection. Thus, roof covers have been in existence since man’s earliest built environment.
WHAT CONSTITUTES AN APPROPRIATE ROOF COVER?
There is no one roof cover that is appropriate for all conditions and climates. It cannot be codified or prescribed, as many are trying to do, and cannot be randomly selected. I, and numerous other consultants, earn a good living investigating roof failures that result from inappropriate roof-cover and system component selection.
There are several criteria for roof-cover selection, such as:
- Compatibility with selected adhesives and the substrate below.
- Climate and geographic factors: seacoast, open plains, hills, mountains, snow, ice, hail, rainfall intensity, as well as micro-climates.
- Compatibility with the effluent coming out of rooftop exhausts.
- Local building-code requirements, such as R-value, fire and wind requirements.
- Local contractors knowledgeable and experienced in its installation.
- Roof use: Will it be just a roof or have some other use, such as supporting daily foot traffic to examine ammonia lines or have fork lifts driven over it?
- Building geometry: Can the selected roof cover be installed with success or does the building’s configuration work against you?
- Building occupancy, relative humidity, interior temperature management, building envelope system, interior building pressure management.
- Building structural systems that support the enclosure.
- Interfaces with the adjacent building systems.
- Environmental, energy conservation and related local code/jurisdictional factors.
- Delivering on the expectations of the building owner: Is it a LEED building? Does he/she want to go above and beyond roof insulation thermal-value requirements to achieve even better energy savings? Is he/she going to sell the building in the near future?
There are many types of roof-cover options for the designer. Wood, stone, asphalt, tile, metal, reed, thatch, skins, mud and concrete are all roof covers used around the world in steep-slope applications. This article will examine the low-slope materials.
The dominant roof covers in the low-slope roof market are:
- Roof sheets joined via tape and adhesive
- Installed: mechanically fastened, fully adhered or ballasted
- Roof sheets joined via heat welding
- Installed: mechanically fastened, fully adhered or plate-bonded (often referred to as the “RhinoBond System”)
- Installed in hot asphalt, cold adhesive or torch application
Thermoplastic: TPO or PVC
Asphaltic: modified bitumen
EPDM (ETHYLENE PROPYLENE DIENE MONOMER)
EPDM is produced in three thicknesses— 45, 60 and 90 mil—with and without reinforcing. It can be procured with a fleece backing in traditional black or with a white laminate on top. The lap seams are typically bonded with seam tape and primer.
EPDM has a 40-year history of performance; I have 30-year-old EPDM roof systems that I have designed that are still in place and still performing. Available in large sheets—up to 50-feet wide and 200-feet long—with factory-applied seam tape, installation can be very efficient. Fleece-back membrane and 90-mil product have superior hail and puncture resistance. Historical concerns with EPDM lap-seam failure revolved around liquid- applied splice adhesive; with seam tape technology this concern is virtually moot. Non-reinforced ballasted and mechanically fastened EPDM roof membrane can be recycled.
EPDM can be installed as a ballasted, mechanically fastened or fully adhered system (see photos 1, 2 and 3). In my opinion, ballasted systems offer the greatest sustainability and energy-conservation potential. The majority of systems being installed today are fully adhered. Ballast lost its popularity when wind codes raised the concern of ballast coming off the roof in high-wind events. However, Clinton, Ohio-based RICOWI has observed through inspection that ballasted roofs performed well even in hurricane-prone locations when properly designed (see ANSI-SPRI RP4).
PHOTOS: HUTCHINSON DESIGN GROUP LTD