RhinoBond Roof Systems

Log Out | Topics | Search Moderators | Register | Edit Profile

Author Message Stephen Wilson Senior Member Username: swilson Post Number: 10 Registered: 02-2019 Posted on Monday, July 26, 2021 - 02:49 pm:    Hi all, Does anyone out there have experience with induction-welded mechanically fastened TPO roof systems (a.k.a, RhinoBond or InvisiWeld)? We have had these come up as VE proposals for fully-adhered systems on several projects recently, but our firm has not used them until recently. Does anyone have any long-term experience with the performance of these systems? Thanks, Steve ken hercenberg Senior Member Username: khercenberg Post Number: 1388 Registered: 12-2006 Posted on Tuesday, July 27, 2021 - 11:22 am:    I know several roof consultants who accept RhinoBond type systems but most do not unless compelled to do so. I usually see it on industrial roofs that are maintained, not on commercial buildings or on critical structures such as health care or data centers. Bottom line from my experience is that mechanical fasteners do 2 things well: 1. They transfer temperature, creating thermal bridges. 2. They eventually work themselves loose due to wind pressures, expansion and contraction, and building movement. One other thing fasteners tend to do when fastening through all board layers below the membrane, especially when gang fastening, is potentially tear through membranes when stepped on or when toolboxes are set down. Depending on deck and membrane types my personal preference is typically to adhere everything from the deck up. You can find good system information on roofnav.com even for projects that aren't FM insured or consider checking DORA. George A. Everding, FCSI, CCS, CCCA, AIA Senior Member Username: geverding Post Number: 926 Registered: 11-2004 Posted on Tuesday, July 27, 2021 - 03:59 pm:    Interesting Ken. I started my career a big fan of mechanically fastened roofing, and ended it a proponent of adhered, as you suggest. Adhesives have gotten so good, not only in roof systems but in many other assemblies, over the last five decades that we have a great deal of comfort in them now, don't we? ken hercenberg Senior Member Username: khercenberg Post Number: 1389 Registered: 12-2006 Posted on Tuesday, July 27, 2021 - 04:13 pm:    So true George. Awhile back I would never have believed that would be my point of view. I guess old dogs can learn after all! Paul Sweet (Unregistered Guest) Unregistered guest Posted on Tuesday, July 27, 2021 - 04:36 pm:    Mechanical fasteners were probably the best way to fasten single ply roofs back when 3" of insulation was a lot and adhesives were hit-or-miss. Another thing they can do is penetrate electrical conduits installed too close to the deck, before the NEC started requiring conduits to be 1 1/2" below the deck. David J. Wyatt, CDT Senior Member Username: david_j_wyatt_cdt Post Number: 337 Registered: 03-2011 Posted on Tuesday, July 27, 2021 - 04:58 pm:    Prior to studying for the IIBEC (formerly RCI) Registered Roof Observer (RRO) exam, my conceptions about adhered vs mechanically-fastened systems were largely confined to how well each attachment method kept the membrane on the building. In the interim, I have learned that building thermal performance and indoor air quality can be affected as well. When wind, HVAC equipment, or stack effect cause low pressure outside the envelope or high pressure within the envelope, mechanically-fastened membranes can billow. This allows moisture-laden air to migrate into the insulation layers, often causing condensation, reduction in thermal efficiency, and an environment for potential mold growth. This is especially a problem in my climate zone (5). It can be prevented when a suitable vapor retarder is appropriately placed in the system, however, vapor retarders are often overlooked in the pursuit of a lower cost roof. I have always favored always adhered systems. As my eyes have been opened to the aforementioned problems with mechanically-fastened systems, I have come to favor adhered systems even more. But, in spite of our well-considered preferences, we are often faced with cost-reducing proposals with the added pressure of having to make up our minds in a hurry. My advice to design teams now is to be prepared for that likelihood by counter-proposing inclusion of a vapor retarder - which often requires a substrate board – in mechanically-fastened systems when vapor intrusion caused by billowing is likely. The inclusion of these safeguards usually offsets any potential money savings. I am not opposed to saving money. Most of the owners I work with have had to earn what they have and I respect that. It’s just that money savings where roofs are concerned usually diminish value and life cycle performance. I wish owners were as concerned about saving money on interior finishes as they are on their roofs. One more thing… a newly-minted RRO like me is not suddenly an expert on roof performance. But I do ask a lot more irritating questions than I used to! Ed Storer Senior Member Username: ed_storer Post Number: 96 Registered: 05-2009 Posted on Tuesday, July 27, 2021 - 08:55 pm:    My mentor at the outset of my career in specifications was fond of saying, "The roof is not the place to save money." The company's "standard roof spec" was a 4-ply coal tar membrane, gravel surfaced, on fiberglass roof insulation and a 2-ply asphalt vapor retarder. He would follow up by saying that the firm had never gone to court for a roofing failure once they went to the "standard spec". Coal tar is no longer in the game, but "The roof is not the place to save money" is still sage advice. I strongly prefer adhered roofs. Ed Storer, CSI Member Emeritus Stephen Wilson Senior Member Username: swilson Post Number: 11 Registered: 02-2019 Posted on Wednesday, July 28, 2021 - 08:11 am:    Thanks, all. I think one of the questions on our end is whether or not the RhinoBond system is a significant improvement over a traditional mechanically fastened system. In theory it seems better since you are not penetrating the membrane with the fastener, but you are still not solving the potential issues of thermal bridging and potential billowing problems. Phil Babinec Senior Member Username: pbabinec Post Number: 40 Registered: 09-2004 Posted on Wednesday, July 28, 2021 - 10:06 am:    Stephen Wilson Senior Member Username: swilson Post Number: 12 Registered: 02-2019 Posted on Wednesday, July 28, 2021 - 10:16 am:    Thanks, Phil... that photo says it all. I'm assuming that is a RhinoBond roof (vs. typical mechanically fastened)? Definitely passing that on to the project architect. ken hercenberg Senior Member Username: khercenberg Post Number: 1390 Registered: 12-2006 Posted on Wednesday, July 28, 2021 - 10:28 am:    I love this forum! Greta Eckhardt Senior Member Username: gretaeckhardt Post Number: 125 Registered: 08-2013 Posted on Wednesday, July 28, 2021 - 10:37 am:    Regarding David Wyatt's recommendation for including a "vapor retarder" I will say that I always specified a vapor retarder membrane on an appropriate substrate because that is generally the best layer to tie into the building enclosure's air barrier system. This also required working with the drafters to make sure the connections were shown. ken hercenberg Senior Member Username: khercenberg Post Number: 1391 Registered: 12-2006 Posted on Wednesday, July 28, 2021 - 10:47 am:    Greta, while vapor retarders serve a very useful purpose in northern areas they can wreak havoc on roofing systems when not needed. I just heard about a roof system over a freezer room where a vapor retarder on the roof deck is believed to have been part of the cause of icicle stalactites forming below the deck. Stephen Wilson Senior Member Username: swilson Post Number: 13 Registered: 02-2019 Posted on Wednesday, July 28, 2021 - 10:54 am:    I would definitely like to more on that situation, Ken. We usually provide vapor retarders to avoid situations like that--i.e., keep the vapor from getting into the insulation layers, condensing, and dripping back through the insulation fasteners. But then again freezer rooms are a whole different climatic ball game! FYI, I work mostly in Climate Zone 5. ken hercenberg Senior Member Username: khercenberg Post Number: 1392 Registered: 12-2006 Posted on Wednesday, July 28, 2021 - 11:08 am:    This was climate zone 4. The presumption is that every time the freezer door opens it allows warm, moist air into the freezer so the vapor drive is actually from the interior upwards. At least that's today's assumption. I'll let you know if I hear any updates. David J. Wyatt, CDT Senior Member Username: david_j_wyatt_cdt Post Number: 338 Registered: 03-2011 Posted on Wednesday, July 28, 2021 - 12:51 pm:    Another important design consideration with mechanically-fastened roof systems is the unusual uplift loads they impose on the roof deck. The structural engineer should be consulted before any agreement is made to change from an adhered system to a mechanically-fastened system. Once again, the additional cost of increasing the yield strength of a deck assembly can negate any savings the owner might hope to gain by changing the membrane attachment method. Mark Gilligan could explain this aspect far better than I. John Bunzick Senior Member Username: bunzick Post Number: 1855 Registered: 03-2002 Posted on Wednesday, July 28, 2021 - 01:50 pm:    The last time I specified a roofing system (admittedly a while now), I spec'd a thin mechanically-attached sheathing to the roof deck, followed by vapor retarder, insulation and membrane all adhered. This avoids the thermal short circuits and billowing, but not the problems with fasteners penetrating the underside of the deck. Though not roofing, I will agree with the sentiments about adhering stuff. In the mid-aughts, I was faced with some rehab window work requiring new flashing. It just wasn't practicable to mechanically attach them, and I was uncomfortable with any "caulk in place" idea. Then I found out that the metal panel siding of Disney Hall in LA was attached with VHB two-sided tape. That turned out to be the ideal solution. It took the design team a little bit to get over the idea that I wanted to use double-stick tape - they're thinking cellophane tape or something. The bond of this material starts low, but increases over a day or so to the point where you really can't remove it, but at the initial installation you are able to pull it off and reposition it. I was really impressed. John Bunzick Senior Member Username: bunzick Post Number: 1856 Registered: 03-2002 Posted on Wednesday, July 28, 2021 - 01:51 pm:    David, wouldn't the uplift loads of the roof be the same regardless of how the membrane is attached? Either way, those loads are going to the deck. I think FM Global designs recognize roof deck attachment as part of the uplift load resistance pathway. David J. Wyatt, CDT Senior Member Username: david_j_wyatt_cdt Post Number: 339 Registered: 03-2011 Posted on Wednesday, July 28, 2021 - 02:48 pm:    John, the way I interpret the information, the uplift point loading associated with a mechanically-fastened system can cause problems that adhered systems don't. Here is an excerpt from the NRCA Roofing Manual: Membrane Roofing Systems, Chapter 2 - Roof Decks: "Most conventional steel deck panels are fabricated from steel with a minimum yield strength of 33 ksi or Grade 33 steel. However, for new construction projects that require FM Approvals’ rating greater than 1-90 or when a mechanically attached membrane’s fastener row spacings exceed 6 feet, FM Global requires a steel roof deck to be fabricated with wide ribs from minimum 22-gauge, high-yield strength Grade 80 steel and have a maximum span of 6 feet." As I mentioned before, a structural engineer, such as Mark Gilligan, might be able to shed more light on this. Phil Kabza Senior Member Username: phil_kabza Post Number: 690 Registered: 12-2002 Posted on Wednesday, July 28, 2021 - 04:12 pm:    We recently specified an induction-welded SPM roof on a multistory office facility on the south side of St. Croix, where the design wind speed of 180 mph is considered too low by our experienced architect client. The region's most experienced roofing contractor requested the system, stating that their experience with Harvey, Maria, and Irma was that these roofs stayed on. I figure folks who are on a first name basis with hurricanes are good ones to consult. Phil Kabza FCSI CCS AIA SpecGuy Specifications Consultants www.SpecGuy.com phil@specguy.com John Bunzick Senior Member Username: bunzick Post Number: 1857 Registered: 03-2002 Posted on Wednesday, July 28, 2021 - 04:55 pm:    David, that makes sense. The concern seems to be fastener pull out. Increased fastener spacing would increase the load on each fastener, hence tougher steel to hold the threads. Phil, I assume the roof you refer to was adhered? Mark Gilligan SE, Senior Member Username: mark_gilligan Post Number: 955 Registered: 10-2007 Posted on Thursday, July 29, 2021 - 02:35 pm:    My experience has been in California, maybe this is different in high wind regions. The engineer should consider wind uplift loads but in most cases this is not a real concern for the building sheathing and the roof structure. Thus detailed calculations of wind uplift forces may not always be calculated.. Architects are not in the habit of asking the structural engineer about wind uplift loads. I cannot recall being asked by an architect about wind uplift loads. If the interior air pressure is positive and the structure and insulation is sufficiently porous this can result in additional uplift forces on the roofing which in turn must be resisted by the mechanical fasteners. gravel and pavers can mitigate these uplift forces. Open buildings and overhangs are subject to higher uplift forces. Michael Chusid, RA FCSI CCS Senior Member Username: michael_chusid Post Number: 615 Registered: 10-2003 Posted on Thursday, July 29, 2021 - 03:16 pm:    To John's comments about adhesives in construction: I used to be wary too. Until I took a look at the engineering of glass curtainwalls that use silicone adhesives for structural connections. The trick is surface preparation and working within tolerances. Michael Chusid, RA FCSI CCS 1-818-219-4937 www.chusid.com www.buildingproduct.guru Mark Gilligan SE, Senior Member Username: mark_gilligan Post Number: 956 Registered: 10-2007 Posted on Thursday, July 29, 2021 - 04:38 pm:    My experience has been in California, maybe this is different in high wind regions. The engineer should consider wind uplift loads but in most cases this is not a real concern for the building sheathing and the roof structure. Thus detailed calculations of wind uplift forces may not always be calculated.. Architects are not in the habit of asking the structural engineer about wind uplift loads. I cannot recall being asked by an architect about wind uplift loads. If the interior air pressure is positive and the structure and insulation is sufficiently porous this can result in additional uplift forces on the roofing which in turn must be resisted by the mechanical fasteners. gravel and pavers can mitigate these uplift forces. Open buildings and overhangs are subject to higher uplift forces.