Case Study Reveals Key Lessons in Roof Design

Photo 1. In order to manufacture materials inside the facility, humidity had to be added to the space in the form of hanging moisture dispensaries. This increased the relative humidity to 90 percent with interior temperatures reaching 90 degrees. Images: Hutchinson Design Group Ltd.

The client said, “The roof leaks in the dead of winter.” Interesting when the exterior ambient temperature is below zero. The client’s firm had purchased the metal building several years earlier and water had come in every winter. A key piece of evidence was that the original building was used for storage. The new entity purchased the building for manufacturing. Not just manufacturing, but manufacturing of medical-grade textiles that require the use of humidity to reduce static electricity. Not just humidity, but 90 percent relative humidity (RH), where visible water is sprayed into the air. (See Photo 1.) Interior temperatures routinely reached 90 degrees. Now, let’s see: 90 degrees with 90 percent RH inside, zero degrees outside, and 6 inches of vinyl face batt insulation compressed at the purlins with aged, open lap seams. Not good. The mission, if I chose to accept it, was to eliminate the leaking on a roof that was watertight.

Proposed Solutions

During my first meeting with the client, I was provided with proposals from roofing contractors and, sad to say, several roof consultants. Proposed solutions ranged from coating the metal, to flute filler and cover board with a mechanically attached thermoplastic membrane, to flute filler, 2 inches of insulation and adhered thermoplastic. None of the proposals identified the interior’s relative humidity and heat as a concern, and thus these issues were not addressed. So, a good part of the morning was spent educating the client as to why none of the proposed solutions would work. Imagine spending big bucks on a roof solution that would have only exacerbated that situation.

Photo 2. Rising humidity passed breaches in the vinyl vapor barrier in the insulation and condensed on the underside of the metal roof panels. The water would then drip down on to the insulation, and eventually the vapor retarder seams would open and water would pour in.

The existing building was a metal building by Kirby (similar to a Butler Building if that helps). The roof was a trapezoidal seam metal roof panel 24 inches wide on a low slope to an offset ridge. The panel runs from ridge to eave were 200 feet to the north and 100 feet to the south. The roof drained to a gutter on the north and lower metal roof on the south. The east and west roof edges were standard metal building rake metal. The walls were vertical metal siding with exposed screws. The roof and metal wall panels were set over vinyl faced insulation draped over purlins. While there was exhausting of the interior air — typically used in the summer — and some provisions for adding exterior air in the winter and summer, there was no overall mechanical control of the interior.

The Key Issue

While a freezer building has extreme energy low trying with every ounce of its being to pull hot humid air in, this structure has extreme energy high trying to “get out.” The warm, humid air is seeking every crack, split in the insulation facer, and open lap seam to move toward equalization. This warm, humid air was making its way to the underside of the metal roof panels, condensing, and running down the underside of the panel until it dropped off.

Figure 1. Typical Roof System Section

After time, the accumulation of the water in the batt insulation created a large belly until the adjacent lap seam broke and large amounts of water came cascading down. Soiled product had to be discarded. With rolls 5 feet wide and a 6 feet diameter, the losses could be substantial. Water on the floor was also a safety issue. Additionally, when this damage occurred the insulation layer now had an opening which sucked in even more interior air; the condensation increased and water dripping to the floor was an even bigger problem. This was occurring in numerous conditions, with the greatest accumulation of water in the insulation near the ridge. (See Photo 2.)

Determining the Solution

Prior to delving into a potential solution, a parti, or overall concept of architectural design, had to be developed. In this case I decided that the metal roof would become the vapor retarder for the new roof. Simple enough. If the metal roof is to become the new vapor retarder, the key was to keep it warm enough so that even if it came in contact with the interior air, it would not result in condensation. We did this by determining the dew point for several insulation scenarios and found that with the batt insulation still in place and 90 percent RH with a temperature of 90 degrees inside, with an exterior design temperature of minus 10 degrees, 6 inches of insulation above the 2.5-inch flute filler was required.

Photo 3. For budget reasons, the liquid flashing seal of the trapezoidal seams was eliminated. As the metal roof had to act as the vapor retarder, a self-adhered membrane was installed first over the trapezoidal seam and fit into the articulated seam with “finger” rollers, and then placed over the center of the panels and fit around the panel striations.

All roof system designs need to be thought of holistically, as the success depends on the sum of all the components working together. So, let’s start with the roof panel and structural system. Designers of metal buildings are notorious for minimizing each and every structural member to lower costs. A structural check found that the existing structure was able to handle the weight of a new roof system. Prior to proceeding, a mechanical fastener pull-out test was performed by Pro-Fastening Systems of Buffalo Grove, Illinois, an Olympic Distributor (need a special or standard anchor, these guys have it). The tests showed that the 22-gauge metal panel was able to engage the buttress thread screw.

To be effective, a vapor retarder needs to be airtight — or for you purists, have extremely low or no permeability at all — and this metal roof had to function as a vapor retarder. The steel roof panel itself is impermeable, but the seams, though mechanically locked, have the potential under interior pressure to allow air to pass through. The seams had to be sealed. The mechanical fasteners penetrating the metal roof panel needed to be sealed as well. The roof transitions at the vertical rake walls, gutter and low roof also needed to be sealed. After looking at the standing seams, it was decided that they could not be assumed to be airtight, so we selected to seal them with a liquid flashing. As the mechanical fasteners would penetrate the panel, a bituminous self-adhering and hopefully self-sealing vapor retarder was placed on the panel. (See Figure 1 and Photo 3.) Transverse laps, removing the ridge cap and infilling the opening were all addressed. The rakes presented unique challenges which took some good thinking on how to seal. Ultimately, it was decided that a combination of removing the rake metal and installing a prefabricated roof curb and membrane vapor retarder would do the trick. (See Figure 2.)

Figure 2. Rake Edge Detail

My initial thought was to begin the thermal layer with a layer of expanded polystyrene (EPS) on the deck designed to fit the trapezoidal seam profile. This left a void at the seams, so the void between the seam and EPS was sealed with spray foam insulation. (See Photo 4.) The insulation was then mechanically fastened. The thickness of the EPS was 3/8 of an inch greater in height than the standing seam to compensate for varying seam heights. Over the EPS, one layer of 2.6-inch fiberglass-coated faced, 25 psi polyisocyanurate insulation was designed to be mechanically fastened to the roof panel. The top layer of insulation was a 2.6-inch fiberglass-coated faced, 25 psi polyisocyanurate insulation, which was designed to be set in full spatter cover flexible polyurethane foam adhesive. A cover board with the receiver facer to which the membrane would be attached was designed to be set in a full coverage of splatter applied polyurethane insulation. (See Photo 5.)

Photo 4. The EPS was cut to fit the panel profile. The joint at the seam was sealed with spray foam insulation.

As the installation was to take place in late fall and during the winter, adhesive use was determined to be challenging if not impossible, so the roof cover selected was a 90-mil Carlisle FleeceBACK black EPDM. The fleece on the membrane would engage with a unique hook and loop facer and reduced by 95 percent the amount of adhesive required. (See Photo 6.) Six-inch seam taped end lap seams with self-adhering cover strips were designed, while the butt seams were also double sealed with 6-inch and 12-inch cover strips.

The rake edge was designed to be sealed at the top of the metal panels and raised with an insulated metal curb. (See Photos 7 and 8.) The wall panels’ reverse batten seams and bowed inward panel were designed to be sealed with a foam closure set in sealant. The architectural sheet metal on the rakes was a four-piece system of fascia and coping. The roof edge gutter was enlarged and reinforced to hold up to solid ice.

Construction

Photo 5. Once the EPS “flute filler” was in place, two layers of 2.6-inch coated fiberglass insulation were mechanically fastened into the standing seam panels. The high-density cover board was then installed in spray foam adhesive.

The project was bid out and AR Commercial of Aurora, Illinois, was selected. Work on the project began in October 2018 and was completed in April 2019. (See Photo 9.) Like any project, various miscellaneous items not anticipated arose, such as extreme cold early in the fall that precipitated the decision to mechanically attach the insulation in lieu of cold adhesive application. I also forgot about the residual water in the existing batt insulation. While we designed for 90 percent RH and temperatures of 90 degrees, we didn’t anticipate the 100 percent RH condition where the soaked batt insulation was located, which resulted in condensation occurring during the deep freeze. You’re never too old to learn something new. The batts were cut open, dried and all is good.

Sometimes you need a good roof over your head to keep you dry, even when it doesn’t rain.

Photo 6. The FleeceBACK 90-mil EPDM sheets were aligned, rolled out, broomed in and rolled.
Photo 7. Following the removal of the existing rake metal, the roof vapor retarder was extended down and over the existing construction and onto the metal roof panel. The contractor came up with an innovative two-piece roof edge curb that allowed for ease of installation.
Photo 8. Following the installation of the interior curb side, which was accomplished with a jig for continuous alignment, the curb was insulated and the exterior cap piece installed.
Photo 9. The finished roof prevented condensation from occurring even when the ambient temperature dropped to minus 28 degrees with wind chills near minus 50 degrees.

About the author: Thomas W. Hutchinson, AIA, FRCI, RRC, CRP, CSI, is a principal of Hutchinson Design Group Ltd. in Barrington, Illinois. For more information, visit www.hutchinsondesigngroup.com.

Boral Roofing Partners With BIMsmith to Create BIM Content for its Roofing Products

Boral Roofing LLC has partnered with BIMsmith to produce Building Information Modelling (BIM) content for its roofing products.

The data-rich digital models produced by the partnership are significant for enabling architects and building professionals to now incorporate Boral Roofing’s clay and concrete tile roofing products directly into their design projects. Each product file is compatible with the industry standard in building design software, Autodesk Revit, making the integration of Boral Roofing into a building project fast and easy for building professionals. Furthermore, the product files include all the data, specifications, and cut sheets that architects and designers need in one place, saving them valuable time and effort in their day-to-day workflow.

In addition to providing standalone BIM content, Boral Roofing has also made its clay and concrete roof tile solutions available on the BIMsmith Forge application, a free cloud tool that allows building professionals to design roofing assemblies layer by layer using real, accurate product data. This integration allows users to build a roofing assembly utilizing any of Boral Roofing’s product lines and add it to their projects in just minutes.

“Boral has long sought to provide roofing solutions with superior performance, durability, energy efficiency, and curb appeal,” said Shannon Delgado, marketing manager at Boral Roofing. “We are excited that the availability of Boral Roofing BIM content through BIMsmith will further aid the architects and designers who commit themselves to these standards of excellence every day.”

“Boral Roofing offers a rare depth of solutions and customization that make them an invaluable resource to the building design process,” said Benjamin Glunz, CEO of BIMsmith. “We are excited to welcome their industry-leading product lines to the BIMsmith platform.”

Boral Roofing’s BIM content can be found at https://market.bimsmith.com/boral. The company’s roofing products may likewise be utilized on the BIMsmith Forge application at https://bimsmith.com.

For more information, visit www.BoralRoof.com.

Ashland Reveals New Corporate Identity and Organizational Culture

Ashland took another step in its plan for the future, revealing its “Always Solving” corporate identity and unveiling the organizational culture that will continue to differentiate the company as it continues its mission.

“We’ve been on a journey since announcing plans to separate Valvoline and Ashland into two standalone companies,” says Bill Wulfsohn, Ashland chairman and chief executive officer. “Today, both companies are positioned for bright futures.”

Along with his leadership team, Wulfsohn developed a strategy which empowers each of Ashland’s chemical businesses to develop its own strategic approach as to where to compete and how to win in their marketplace. Each will employ its own core competencies in problem-solving that brings value to customers. Together as one global team, Ashland will build an organization focused on innovation, operations, and capital deployment. Its foundation will continue to be built on operations. Ashland will continue fostering growth through innovations and sales opportunities, and continue capturing value delivered to customers while driving cost competitiveness.

The most public facing element of the evolution of Ashland, is its new corporate identity – Always Solving – which reflects the company’s positioning and people across diverse industries as broad as pharmaceuticals to automotive, personal care to paints, adhesives to biofunctionals, and more.

“Now is the time for Ashland to communicate the nature of who we are and what sets our employees apart. We’re a company of solvers who develop solutions to complex problems in applied chemistry, pushing the boundaries of what’s possible, and advancing the competitiveness of our customers across industries,” states Carolmarie Brown, Ashland director global marketing and business communications.

The positioning illustrates how Ashland acts as a partner to its customers, providing solutions that bring value to its business partners. In particular, the company is focused on innovations for growing market positions in segments such as pharmaceuticals, personal care and paints and coatings.

Today and moving forward, Ashland embodies how its people are distinguished by their ability to apply specialized chemistry with a disciplined approach that increases the efficacy, refines the usability, adds to the allure, ensures the integrity, and improves the profitability of their customers’ products and applications. Each of these qualities are manifested in different ways for different industries, and together, its people around the globe are always solving, to improve customers’ products. “In Ashland we bring together different backgrounds, different disciplines, different points of view, and we operate as one team with a sense of purpose,” said Luis Fernandez-Moreno, senior vice president of Ashland and president of the Chemicals Group.

Along with its strategy and identity is the articulation and implementation of a collective Ashland Way, its corporate culture, which is “to respect, protect, and advance the people we work with, companies we serve, shareholders who invest in our future, communities we’re a part of, and the planet we share.”

The Ashland Way will drive business growth and shape an organization of which employees will want to be a part. Values of safety, integrity, partnership and passion will guide behavior each day.

“We have a common understanding of how we operate, think, manage, encourage and act in order to build an organization and improve the world through solutions based on the application of specialty ingredients and materials,” Wulfsohn says.

Ashland has a focus on operations and has been committed to doing business with integrity and respect for all people and the world. The company has made formal commitments to improve the environmental, health, safety and security performance for facilities, processes and products throughout the entire operating system. Forty-six Ashland sites have received Responsible Care certification, including three facilities earlier this year.