Understanding and Installing Insulated Metal Panels

IMP installation

IMP installation typically occurs once the steel frame is in place. The more common vertical installation allows for faster close-in for interior trade work. Photos: Metl-Span

Insulated metal panels, or IMPs, incorporate a composite design with foam insulation sandwiched between a metal face and liner. IMPs form an all-in-one-system, with a single component serving as the exterior rainscreen, air and moisture barrier, and thermal insulation. Panels can be installed vertically or horizontally, are ideal for all climates, and can be coated with a number of high-performance coating systems that offer minimal maintenance and dynamic aesthetic options.

The Benefits of IMPs

At the crux of the IMP system is thermal performance in the form of polyurethane insulation. Panel thicknesses generally range from 2 to 6 inches, with the widest panels often reserved for cold storage or food processing applications. IMPs provide roughly three times the insulation value of field-assembled glass fiber systems, and panel thickness and coating options can be tailored to meet most R-value requirements.

IMPs offer a sealed interior panel face to create a continuous weather barrier, and the materials used are not conducive to water retention. Metal—typically galvanized steel, stainless steel or aluminum—coupled with closed-cell insulation creates an envelope solution impervious to vapor diffusion. Closed-cell insulation has a much denser and more compact structure than most other insulation materials creating an advantage in air and vapor barrier designs.

Time, budget and design can all be looming expectations for any building project. A valuable characteristic of IMPs is their ability to keep you on time and on budget while providing design flexibility to meet even the toughest building codes. The unique single-source composition of insulated metal panels allows for a single team to accomplish quick and complete enclosure of the building so interior trades can begin. This expedites the timeline and streamlines the budget by eliminating the need for additional teams to complete the exterior envelope and insulation.

Minimizing Moisture

The seams function both as barrier and pressure-equalized joint, providing long-term protection that requires minimal maintenance. Multiple component systems often rely on the accurate and consistent placement of sealant and may also require periodic maintenance. In addition, with IMPS a vented horizontal joint is designed for pressure equalization, and, even in the presence of an imperfect air barrier, the pressure-equalized joinery maintains the system’s performance integrity. With multi component systems, imperfections can lead to moisture infiltration.

The real damage occurs when water enters through a wall and into a building becoming entrapped—which leads to corrosion, mold, rot, or delaminating. Unlike IMPs, some multi-component wall systems include a variety of different assembly materials that may hold water, like glass fiber or paper-faced gypsum. When those materials get wet, they can retain water, which can result in mold and degradation.

Installation

Typically, IMP installation is handled by crews of 2-4 people. Very little equipment is needed other than standard construction tools including hand drills, band and circular saws, sealant guns, and other materials. The panels can be installed via the ground or from a lift, and materials can be staged on interior floors or on the ground level. Panel installation typically occurs once the steel frame is in place and prior to interior fit out. The more common vertical installation allows for faster close-in for interior trade work.

Metl-Span CFR insulated metal standing seam roof panels

Metl-Span CFR insulated metal standing seam roof panels combine durable interior and exterior faces with exceptional thermal performance. Photos: Metl-Span

IMPs are often installed using concealed clips and fasteners that are attached to the structural supports (16 gauge minimum wall thickness tubes or stud framing). The panels are typically installed bottom to top and left to right, directly over the steel framing. No exterior gypsum or weather barriers are required, as these panels act as the building’s weather barriers.

The product’s high strength-to-weight ratio allows for longer installation spans and reduced structural costs. The metal skins act as the flange of a beam, resisting bending stress, while the foam core acts as the web of the beam, resisting shear stress. This important aspect also contributes to a long product life cycle.

Design Flexibility

IMPs offer a unique combination of aesthetic design options, including mitered panel edges, and a vast array of profiles, textures and reveal configurations. Flat wall profiles are ideally suited for designers seeking a monolithic architectural façade without sacrificing performance elements. The beautiful, flush panels have become a mainstay in projects in a number of high-end architectural markets.

The 35,000-square-foot AgroChem manufacturing facility in Saratoga Springs, N.Y.

The 35,000-square-foot AgroChem manufacturing facility in Saratoga Springs, N.Y., showcases vertically installed Metl-Span CF36 insulated metal panels. Photos: Metl-Span

Striated or ribbed wall profiles are more common in commercial and industrial applications. The products offer bold vertical lines for a distinctive blend of modern and utilitarian design, while continuing flawless symmetry from facade to facade, or room to room on exposed interior faces. Ribbed panels also work in tandem with natural lighting to create impactful designs. Different textures, such as embossed or simulated stucco finish, add dimensional nuance and contrast to projects of all shapes and sizes.

IMPs are offered in an unlimited palette of standard and custom colors to meet any aesthetic requirement, as well as energy-efficient solar reflectivity standards. Panels are typically painted with a polyvinylidene fluoride (PVDF) coating with optional pearlescent and metallic effects, and can even simulate expensive wood grains and natural metals. PVDF finishes offer exceptional performance characteristics that can be tailored to meet most any project needs, including saltwater environments and extreme weather conditions.

Roof Configurations

For all the above reasons, IMPs have also become a popular building product for roofing applications. Insulated metal standing seam roof panels provide the desired aesthetic of traditional single-skin metal standing seem roofs with added thermal performance. Standing seam roof panels feature a raised lip at the panel joinery, which not only enhances overall weather resistance but provides the desired clean, sleek sightlines.

IMP installation

IMP installation typically occurs once the steel frame is in place. The more common vertical installation allows for faster close-in for interior trade work Photos: Metl-Span

The systems typically feature field-seamed, concealed fasteners that are not exposed to the elements. Just like their wall panel counterparts, insulated metal standing seam roof panels are available in a variety of thicknesses and exterior finishes.

Another popular insulated metal roof application showcases overlapping profile panels. The product’s overlapping, through-fastened joinery allows for quick installation in roof applications, resulting in reduced labor costs and faster close-in.

Finally, insulated metal roof deck panel systems combine the standard steel deck, insulation, and substrate necessary for single-ply membranes or non-structural standing seam roof coverings. The multi-faceted advantages of this system include longer spans between supports, superior deflection resistance, and a working platform during installation.

Insulated metal wall and roof panels offer an exceptional level of value when compared to traditional multi-component wall systems. The product’s unique single-component construction combines outstanding performance with simple and quick installation, a diverse array of aesthetic options, and the quality assurance of a single provider.

Definition of Resilience: Hospital Provides a Lesson in Preparing for Weather Events

Staten Island University Hospital escaped major damage during Hurricane Sandy. The city of New York allocated $28 million to fund the hospital’s resiliency plan, and the state contributed an additional $12 million.

Staten Island University Hospital escaped major damage during Hurricane Sandy. The city of New York allocated $28 million to fund the hospital’s resiliency plan, and the state contributed an additional $12 million.

Almost five years ago, Hurricane Sandy bore down on New York City with winds that reached gusts of 100 miles an hour and a storm surge 16 feet above normal that flooded huge parts of the city. Entire neighborhoods lost electricity for several days, the Stock Exchange closed during and immediately after the storm, and scuba divers were called in to assess damage in parts of the city’s submerged subway system.

Staten Island, one of New York’s five boroughs, was heavily damaged. Its position in New York Harbor, at the intersection of the coastlines of Long Island and New Jersey, leaves the island particularly exposed to storm surge during extreme weather events. A geologist from Woods Hole Oceanographic Institution in Massachusetts described Staten Island as being, “at the end of, basically, a big funnel between New Jersey and New York.”

Staten Island University Hospital almost miraculously escaped major damage, despite flood waters coming within inches of it doors. The hospital stayed open during and after Hurricane Sandy, continuing to provide vital services despite the storm. The hospital is home to the largest emergency room on Staten Island, and houses more than one third of the borough’s in-patient beds. New York Mayor DeBlasio has called the hospital, “a truly decisive healthcare facility—even more so in times of crisis.”

While both hospital and city officials were relieved that the facility had escaped Sandy largely unharmed, the lesson that Sandy delivered was taken to heart: major mitigation efforts were needed if the hospital expected to survive similar storms in the future. With this in mind, the city of New York allocated $28 million to fund the hospital’s resiliency plan, with the state kicking in an additional $12 million.

The money is being spent on three major projects to better prepare the hospital for future storms: the elevation of critical building power and mechanical systems, the installation of sanitary holding tanks and backflow prevention, and the installation of major wind resiliency and roofing improvements. 

Resilient Design

The Staten Island experience, and the plan to upgrade its ability to withstand major weather events, is hardly unique. Nationwide, resilient design has become a major focus of the construction community.

Hurricane Sandy certainly intensified the sense of urgency surrounding the need for resilience. But well before that, Hurricane Katrina, in 2005, provided a tragic case study on the fragility of seemingly stable structures, as the storm brought a small, poor southern city to the brink of chaos and devastated entire neighborhoods. While these two hurricanes drew national and international attention, communities throughout the country have also been dealing with frequent, erratic and intense weather events that disrupted daily life, resulting in economic losses and, all too often, the loss of human life. These emergencies may include catastrophic natural disasters, such as hurricanes, earthquakes, sinkholes, fires, floods, tornadoes, hailstorms, and volcanic activity. They also refer to man-made events such as acts of terrorism, release of radioactive materials or other toxic waste, wildfires and hazardous material spills.

The focus, to a certain degree, is on upgrading structures that have been damaged in natural disasters. But even more, architects and building owners are focusing on building resilience into the fabric of a structure to mitigate the impact of future devastating weather events. And, as with the Staten Island Hospital, the roof is getting new attention as an important component of a truly resilient structure.

The resilience of the roofing system is a critical component in helping a building withstand a storm and rebound quickly. In addition, a robust roofing system can help maintain a habitable temperature in a building in case of loss of power. Photo: Hutchinson Design Group.

The resilience of the roofing system is a critical component in helping a building withstand a storm and rebound quickly. In addition, a robust roofing system can help maintain a habitable temperature in a building in case of loss of power. Photo: Hutchinson Design Group.

So, what is resilience, how is it defined, and why is it important to buildings in differing climates facing unique weather events? The Department of Homeland Security defines resilience as “the ability to adapt to changing conditions and withstand and rapidly recover from disruption due to emergencies.” The key words here are “adapt” and “rapidly recover.” In other words, resilience is measured in a structure’s ability to quickly return to normal after a damaging event. And the resilience of the roofing system, an essential element in protecting the integrity of a building, is a critical component in rebounding quickly. In addition, a robust roofing system can provide a critical evacuation path in an emergency, and can help maintain a habitable temperature in a building in case of loss of power.

According to a Resilience Task Force convened by the EPDM Roofing Association (ERA), two factors determine the resiliency of a roofing system: durable components and a robust design. Durable components are characterized by:
Outstanding weathering characteristics in all climates (UV resistance, and the ability to withstand extreme heat and cold).

  • Ease of maintenance and repair.
  • Excellent impact resistance.
  • Ability to withstand moderate movement cycles without fatigue.
  • Good fire resistance (low combustibility) and basic chemical resistance.
  • A robust design that will enhance the resiliency of a roofing system should incorporate:

  • Redundancy in the form of a backup system and/or waterproofing layer.
  • The ability to resist extreme weather events, climate change or change in building use.
  • Excellent wind uplift resistance, but most importantly multiple cycling to the limits of its adhesion.
  • Easily repaired with common tools and readily accessible materials.
  • More Information on Resilient Roofing

    The Resilience Task Force, working with the ERA staff, is also responding to the heightened interest in and concern over the resilience of the built environment by launching EpdmTheResilientRoof.org. The new website adds context to the information about EPDM products by providing a clearinghouse of sources about resilience, as well as an up-to-date roster of recent articles, blog posts, statements of professional organizations and other pertinent information about resilience.

    “This new website takes our commitment to the construction industry and to our customers to a new level. Our mission is to provide up-to-date science-based information about our products. Resilience is an emerging need, and we want to be the go-to source for architects, specifiers, building owners and contractors who want to ensure that their construction can withstand extreme events,” said Mike DuCharme, Chairman of ERA.

    EPDM roofs can be easily repaired and restored without the use of sophisticated, complicated equipment. Photo: Hutchinson Design Group.

    EPDM roofs can be easily repaired and restored without the use of sophisticated, complicated equipment. Photo: Hutchinson Design Group.

    EPDM and Resiliency

    The Resilience Task Force also conducted extensive fact finding to itemize the specific attributes of EPDM membrane that make it a uniquely valuable component of a resilient of a roofing system:

  • EPDM is a thermoset material with an inherit ability to recover and return to its original shape and performance after a severe weather event.
  • EPDM has been used in numerous projects in various geographic areas from the hottest climate in the Middle East to the freezing temperatures in Antarctica and Siberia.
  • After decades of exposures to extreme environmental conditions, EPDM membrane continues to exhibit a great ability to retain the physical properties and performances of ASTM specification standards.
  • EPDM is the only commercially available membrane that performs in an unreinforced state, making it very forgiving to large amounts of movement without damage and potentially more cycles before fatiguing.
  • EPDM offers excellent impact resistance to hail, particularly when aged.
  • EPDM is resistant to extreme UV exposure and heat.
  • EPDM far exceeded the test protocol ASTM D573 which requires materials to pass four weeks at 240 degrees Fahrenheit. EPDM black or white membranes passed 68 weeks at these high temperatures.
  • Exposed EPDM roof systems have been in service now for 50-plus years with little or no surface degradation.
  • EPDM is versatile.
  • EPDM can be configured in many roofing assemblies, including below-grade and between-slab applications.
  • EPDM is compatible with a broad range of construction materials/interfaces/conditions, making it a good choice for areas that may encounter unique challenges.
  • EPDM can be exposed to moisture and intense sunlight or totally immersed in salty water.
  • EPDM can easily be installed, repaired and restored following simple procedures without the use of sophisticated, complicated equipment.
  • EPDM can be repaired during power outages.
  • For further information about the need for resilience, and the appropriate use of EPDM in resilient structures, visit EPDMTheResilientRoof.com.

    Virginia Tech Study Measures the Impact of Membranes on the Surrounding Environment

    Equipment tripods are set up to hold air temperature and EMT temperature sensors.

    Equipment tripods are set up to hold air temperature and EMT temperature sensors.

    For much of the past decade, the debate over when and where to install reflective roofing has been guided by two basic assumptions: first, since white roofs reflect heat and reduce air conditioning costs, they should be used in hot climates. Second, since black membranes absorb heat, they should be used in cool-to-colder climates to reduce heating costs. This reasoning has been broadly accepted and even adopted in one of the most influential industry standards, ASHRAE 90.1, which requires reflective roofing on commercial projects in the warm-weather portions of the United States, Climate Zones 1–3.

    But as reflective membranes have become more widely used, there has been a growing awareness that the choice of roof color is not simply a matter of black or white. Questions continue to be debated not only about the performance and durability of the different types of membranes, but on the impact of other key components of the roof system, including insulation and proper ventilation. The issue of possible condensation in cooler or even cold climates is garnering more attention. Given these emerging concerns, the roofing community is beginning to ask for more detailed, science-based information about the impact of reflective roofing.

    One recent area of inquiry is centering on the impact of “the thermal effects of roof color on the neighboring built environment.” In other words, when heat is reflected off of a roofing surface, how does it affect the equipment and any other structures on that roof, and how might the reflected heat be impacting the walls and windows of neighboring buildings? Put another way, where does the reflected heat go?

    THE STUDY

    To help answer those questions, the Center for High Performance Environments at Virginia Tech, supported by the RCI Foundation and with building materials donated by Carlisle Construction Materials, designed and implemented a study to compare temperatures on the surface and in the air above black EPDM and white TPO membranes. In addition, the study compared temperatures on opaque and glazed wall surfaces adjacent to the black EPDM and white TPO, and at electrical metallic tubing (EMT) above them.

    Specifically, the Virginia Tech study was designed to answer the following questions:

    • What is the effect of roof membrane reflectivity on air temperatures at various heights above the roof surface?
    • What is the effect of roof membrane reflectivity on temperatures of EMT at various heights above the roof surface?
    • What is the effect of roof membrane reflectivity on temperatures of opaque wall surfaces adjacent and perpendicular to them?
    • What is the effect of roof membrane reflectivity on temperatures of glazed wall surfaces adjacent and perpendicular to the roof surface?

    To initiate the study, the Virginia Tech team needed to find an existing roof structure with the appropriate neighboring surfaces. They found a perfect location for the research right in their own backyard. The roof of the Virginia-Maryland College of Veterinary Medicine at Virginia Tech was selected as the site of the experiment because it had both opaque and glazed wall areas adjacent to a low-slope roof. In addition, it featured safe roof access.

    In order to carry out the study, 1.5 mm of reinforced white TPO and 1.5 mm of non-reinforced black EPDM from the same manufacturer were positioned on the roof site. A 12-by-6-meter overlay of each membrane was installed adjacent to the opaque wall and a 6-by-6-meter overlay of each was installed next to the glazed wall. At each “location of interest”—on the EPDM, on the TPO, and next to the opaque and glazed walls—the researchers installed temperature sensors. These sensors were placed at four heights (8, 14, 23, and 86 centimeters), and additional sensors were embedded on the roof surface itself in the TPO and EPDM. Using these sensors, temperatures were recorded on bright, sunny days with little or no wind. The researchers controlled for as many variables as possible, taking temperature readings from the sensors on and above the EPDM and TPO on the same days, at the same time, and under the same atmospheric conditions.

    The roof of the Virginia-Maryland College of Veterinary Medicine at Virginia Tech is the site of the experiment because it has opaque and glazed wall areas adjacent to a low-slope roof.

    The roof of the Virginia-Maryland College of Veterinary Medicine at Virginia Tech is the site of the experiment because it has opaque and glazed wall areas adjacent to a low-slope roof.

    THE RESULTS

    The output from the sensors showed that at the surface of the roof, the black membrane was significantly hotter than the white membrane, and remained hotter at the measuring points of 8 cm and 14 cm (just over 3 inches and 5.5 inches, respectively). However, the air temperature differences at the sensors 23 centimeters (about 9 inches) and 86 centimeters (just under three feet) above the surface of the roof were not statistically significant. In other words, at the site the air temperature just above the white roof was cooler, but beginning at about 9 inches above the roof surface, there was no difference in the temperature above the white and black membranes.

    On the precast concrete panel adjacent to the TPO and EPDM, temperatures were warmer next to the TPO than adjacent to the EPDM, leading the study authors to hypothesize that the TPO reflected more heat energy onto the wall than did the EPDM. Exterior glazing surface temperatures were found to be approximately 2 degrees Celsius hotter adjacent to the TPO overlay as compared to the EPDM overlay.

    Elizabeth Grant led the team that designed and implemented the study. She says her findings show that you need to take the entire environment into account when designing a roof system. “You need to think about what’s happening on top of the roof,” she says. “Is it adjacent to a wall? Is it adjacent to windows? Is it going to reflect heat into those spaces?”

    Samir Ibrahim, director of design services at Carlisle SynTec, believes the study results will help frame additional research. “These findings are an important reminder that the full impact of reflective roofing on a building and on surrounding buildings is not fully understood,” he says. “Additional research and joint studies, covering different climatic conditions, are certainly warranted to broaden the knowledge and understanding of the true impact on the built-environment.”

    Two Commercial Installations Are Honored with ARMA’s QARC Awards

    Advanced Roofing Inc. installed two new roofs at a luxury retired-living community in Palm Beach Gardens. These projects were Silver Award winners in ARMA’s 2016 QARC Awards.

    Advanced Roofing Inc. installed two new roofs at a luxury retired-living community in Palm Beach Gardens. These projects were Silver Award winners in ARMA’s 2016 QARC Awards.

    Commercial roofs are the workhorses of a building system. They endure wind, rain, hail and foot traffic while serving as an important line of defense between the outside world and a building’s occupants. If inhabitants never consider the roof over their heads, it means the roof system is doing its job well.

    The Washington, D.C.-based Asphalt Roofing Manufacturers Association (ARMA) showcases these hardworking but rarely celebrated systems in its annual Quality Asphalt Roofing Case- study (QARC) Awards program. Each year, the organization seeks the top asphalt roofing projects in North America that demonstrate durability and high performance, as well as beauty. The QARC awards honor a Gold, Silver and Bronze winning project that illustrates the benefits of asphalt roofing.

    The Silver Winner of ARMA’s 2016 QARC Awards is a prime example of what a commercial roofing system must stand up to while remaining water-resistant and durable. Advanced Roofing Inc. (ARI), which has service areas throughout much of Florida, was hired to install two new roofs at a luxury retired-living community in Palm Beach Gardens. These reroofs were completed in 2015 and were submitted to ARMA’s awards program.

    The two buildings in this community were originally built in the 1990s and were found to have numerous issues that demanded immediate attention when new management reviewed the property. The area’s hot climate requires many air-conditioning units on the roof that frequently have to be serviced. This aspect of a commercial roof can be overlooked by building owners but has a significant impact on its service life and performance. Because HVAC units and related equipment are heavy and may require frequent maintenance that brings extensive foot traffic, they can cause a roof system to deteriorate faster than normal. That was the case with the existing roofs in this living community.

    Toward the end of the roofs’ service lives, temporary fixes, like patching and coatings, were made. These regular repairs only increased the operational budget while the core issues remained unresolved. According to Jessica Kornahrens, project manager at ARI, “The existing roofing system was at risk of a failure that could potentially close the building and leave its elderly residents without a home.”

    ARI was hired by the new building owner and property manager to tear off the existing roofs of these two buildings and install an asphalt roofing system on each. Because of the significant durability required by the new roofs, the roofing contractor chose a high-performance three-ply modified bitumen asphalt roofing system.

    The two buildings in the retirement facility were still occupied during the reroof project, creating an additional challenge during installation, but the work came in on schedule and within budget.

    The two buildings in the retirement facility were still occupied during the reroof project, creating an additional challenge during installation, but the work came in on schedule and within budget.


    “We knew that this type of redundant, multi-layered system would protect these buildings long-term despite the high foot traffic and heavy equipment they have to stand up to while also meeting the project budget,” Kornahrens says. “This particular system also has a Miami-Dade Notice of Acceptance with testing and approvals for Florida’s high-velocity hurricane zone.”

    Between foot traffic and harsh weather, the contractors knew this asphalt roofing system was up to the task.

    Challenging Installation

    Before they could begin the project, ARI had to first stop the existing leaks in the first 45,900-square-foot building and the second 51,000-square-foot building, followed by a tear-off of the roof system down to the light- weight concrete. ARI fastened the modified anchor sheet with twin-lock fasteners directly into the lightweight insulated concrete deck and then torch applied an interply and fire-retardant granulated cap sheet.

    Photos: Smith Aerial Photography

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    Avoid Problems with Skylights through Proper Installation

    As trendy as they are for green building and demonstrably beneficial for energy savings
    through daylighting, skylights are sometimes viewed with a certain trepidation by roofing
    contractors. After all, skylights are essentially holes in the roof with the potential to compromise roofing workers’ handiwork by providing unintended leakage paths.

    Proper installation is essential to realizing designed-in leak-free performance and can vary by type of roofing involved and the type of skylight. It is recommended to always refer to and use the skylight manufacturer’s instructions that are specific to the roof system being installed. Of course, applicable code requirements supersede any instructions to the contrary.

     A commercial skylight provides more daylight and improves an indoor recreational setting. PHOTO: Structures Unlimited

    A commercial skylight provides more daylight and improves an indoor recreational setting. PHOTO: Structures Unlimited

    AAMA 1607-14, “Installation Guidelines for Unit Skylights”, which is an industry consensus guideline published by the Schaumburg, Ill.-based American Architectural Manufacturers Association, intended for use when manufacturer instructions are absent or incomplete, provides basic step- by-step installation instructions for 19 different ways to integrate various roofing materials, underlayment, flashing and skylight-mounting configurations to preserve the drainage plane. This must be the overriding intent of any installation protocols.

    Note that some roofing contractors warrant their work against leakage, and skylight installation should not compromise or void such warranties. When in doubt, independent installers should confer with the roofing contractor.

    INSTALLATION SUPPLIES

    Proper installation begins with selection and use of the proper supplies—notably sealants, fasteners and flashing.

    SEALANT SELECTION
    If sealants are recommended by the manufacturer, follow the manufacturer’s specifications. When the manufacturer is silent about the use of sealants and the installation guidelines dictate their use, the following recommendations should be observed:

    • Compatibility—The sealant must not adversely react with or weaken the material it contacts.
    • Adhesion—The sealant must have good long-term adhesion. Surface preparation, cleaning procedures and, in some cases, primers are recommended by the sealant manufacturer.
    • Service Temperature—If the installation location involves elevated ambient temperatures, the sealant should exhibit corresponding service temperature performance.
    • Durability—The sealant must be capable of maintaining the required flexibility and integrity over time.
    • Application—Proper bead size and other application details should be followed to ensure a well-performing joint. Improper use of sealants can dam water pathways, so an important rule of thumb is not to block any weep holes that may be in the skylight system.

    Typically, sealant or roofing cement is applied around the perimeter of the rough opening (deck mount) or the flange of self-flashing units or the top edge of a mounting frame. However, some skylights are designed with integral flashing flanges to be installed without the need for sealants.

    It is also possible to utilize rolled roofing membranes as a substitute for sealants or plastic roofing cement.

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    A Michigan Contractor Is Challenged to Recreate a Roof’s 40-year-old Mural

    Kevin Clausen has faced a lot of challenges during his 30 years at Great Lakes Systems, a Jenison, Mich.-based construction company specializing in single-ply commercial roofs. But when he received a call several years ago from a Kent County official about an unusual upcoming project, Clausen knew he might be taking on a challenge unlike any other.

    Artist Alexander Calder created the 127-square-foot red, black and white mural painted on the roof of the Kent County Administration building.

    Artist Alexander Calder created the 127-square-foot red, black and white mural painted on the roof of the Kent County Administration building.

    Kent County is home to Grand Rapids, Mich. To understand the challenge that Clausen was about to face, it’s important to understand a little Grand Rapids history. In the late 1960s, swept along by the tide of enthusiasm for urban renewal, the city demolished 120 buildings in its aging downtown core and built a new City Hall and County Administration building, surrounded by a concrete plaza. The new government buildings were designed by architects who were shaped by mid-century ideas of good urban design: sleek, boxy single-use structures, easily accessed by automobile and, therefore, providing ample parking. Pedestrians were something of an afterthought.

    At about the same time, the National Endowment for the Arts initiated its Art in Public Places Program. There was general agreement in Grand Rapids that the broad plaza in front of the new buildings seemed empty and generally lacked visual interest. The city applied for a grant to support the funding of a monumental sculpture to serve as a focal point for its new plaza and selected renowned sculptor Alexander Calder for the commission. Two years later, Calder’s sculpture—bright red, 43- feet tall, 54-feet long, 30-feet wide, weighing 42 tons—took its place on the central plaza. It was named “La Grande Vitesse”, which roughly translates into “Grand Rapids”. For obvious reasons, the broad plaza has been called Calder Plaza—and has been the focus of controversy ever since.

    The Calder sculpture at ground level on the plaza inspired another important work of art in the area. The flat, unadorned roof of the administration building adjacent to the plaza was drawing attention for the wrong reasons. It was easily viewed from the nearby taller buildings, including the new City Hall, and several city administrators thought some sort of added visual element was necessary for the space. Calder again was pressed into service and designed a large mural for the roof of the administration building. When it was completed in 1974, the 127-square-foot red, black and white mural painted on the roof of the Kent County Administration building was the largest Calder painting in the world.

    A DURABLE ROOF

    Fast-forward three decades and the aging modified bitumen roofing membrane, which supported the Calder mural, had weathered badly and was in need of repair or replacement. The challenge? How to repair the roof and still preserve the Calder mural. Given the deteriorated condition of the roofing membrane, a complete tear-off was required. Basically, the task at hand was to replace the canvas of a painting and recreate the painting, maintaining its original appearance.

    Great Lakes Systems, Jenison, Mich., was challenged to recreate the Calder mural on a new EPDM roof after tearing off the modified bitumen roof on which the mural was originally painted.

    Great Lakes Systems, Jenison, Mich., was challenged to recreate the Calder mural on a new EPDM roof after tearing off the modified bitumen roof on which the mural was originally painted.

    The team at Great Lakes Systems has a long track record of doing work for Kent County, including the jail, juvenile facility and several libraries. Therefore, county leaders turned to Great Lakes Systems when they realized they need- ed a creative solution to repair their unique roof. Clausen says the county wanted to preserve the mural, but a long-lasting, durable roof was a top priority. “They definitely wanted a high-quality roof,” he says.

    The project faced other constraints, in addition to the painted surface. The administration building is located in a prominent spot in the middle of downtown Grand Rapids, near the museum dedicated to former President Gerald Ford and adjacent to two major expressways. No interruption of normal activities could be allowed—either on the plaza or in the building supporting the Calder mural. And—perhaps most challenging—Great Lakes Systems was given three weeks to complete the project before the inaugural ArtPrize competition would take over much of downtown Grand Rapids. That meant the team would have two weeks for the roof installation, leaving one week to repaint the mural. This was less than half the time usually required for a comparable project.

    For Clausen, one part of the project was easy. He had used EPDM membrane on a variety of prior projects for county buildings, and county officials had been pleased with the results, especially the balance of cost-effective installation and long service life. “We looked at other membranes, given the nature of the project, but we always came back to EPDM, given its 30-year plus lifespan,” Clausen notes. “If we have to paint again, that’s OK, but we don’t want to reroof.”

    For this project, fully adhered EPDM, as well as insulation ad- hered to the concrete deck, offered two important benefits: a painting surface that would be appropriate for the repainted mural and minimal noise (compared to a mechanically attached system) so that work in the building below could continue as normal.

    Great Lakes Systems used 60-mil EPDM to replace the aging modified bitumen system. The 18,500-square-foot roof was backed by two layers of 2-inch polyiso insulation, and the EPDM membrane was covered with an acrylic top coat to provide a smooth surface for the new painting. The top coat matched the three colors of the mural—red, black and white. The red was a custom tinted acrylic paint deemed to be compatible with the EPDM membrane and the black and white acrylic top coat provided by the EPDM manufacturer.

    Great Lakes Systems took aerial photos of the existing roof, created a grid of the roof and—scaling the design from the photos—recreated the mural exactly, a sort of large-scale paint- by-number approach.

    Great Lakes Systems took aerial photos of the existing roof, created a grid of the roof and—scaling the design from the photos—recreated the mural exactly, a sort of large-scale paint- by-number approach.

    A BEAUTIFUL ROOF

    The Great Lakes Systems’ team applied a creative approach to recreate the mural, adhering carefully to the original design. Because the county used the same colors on its street signs as in the original mural, color codes were available to allow the team to access colors that were identical to those specified by Calder.

    Great Lakes Systems took aerial photos of the existing roof, created a grid of the roof and—scaling the design from the photos—recreated the mural exactly, a sort of large-scale paint-by-number approach. The most intricate part of the painting was the layout. Although some free-hand painting had to be done along several jagged edges, the team painstakingly followed the scaled grid and applied chalk lines to outline the original design on the repaired roof. Roller applications were used at the border of the chalk lines to define individual spaces and mark the stopping and starting points for the different colors. Following this “outlining” work, the large areas were sprayed to complete the painting process. The three-man painting crew finished the job with several days to spare, helped along with very good weather.

    The roofing project was an informal jump-start toward reimagining uses for Calder Plaza. This past summer, Grand Rapids residents were given the opportunity to voice their preferences for new landscaping for the plaza, provide input for activities that would attract more families and children, and generally make the space more pedestrian friendly. The new proposals are generating excitement and enthusiasm in Grand Rapids. As the new plans become reality, the citizens of Grand Rapids can be assured the Calder mural and the roof supporting it will be doing their part to add beauty and shelter to Calder Plaza and its buildings for decades to come.

    Roof Materials

    60-mil EPDM: Firestone Building Products Co.
    2-inch Polyiso Insulation: Firestone Building Products
    Black and White Acrylic Top Coat: Firestone Building Products

    PHOTOS: Great Lakes Systems

    Contemporary Materials Are Used to Preserve a Historically Significant 1889 House

    In my capacity as a historic preservation contractor and consultant, I am often afforded the opportunity to become involved in exciting and challenging projects. Recently, my firm was awarded the contract to restore the clay tile roof turrets at Boston’s Longy School of Music’s Zabriskie House. Now part of Bard College, Longy School’s Zabriskie House is actually the historic Edwin H. Abbot House with a sympathetically designed addition built in the 1980s. The deteriorated condition of the original house’s turrets, as well as lead-coated copper gutter linings and masonry dormers, had attracted the attention of the Cambridge Historic Commission, and a commitment to the proper restoration of these systems was struck between the commission, building owner and a private donor.

    The hipped roof turret on the building’s primary façade was in need of serious attention.

    The hipped roof turret on the building’s primary façade was in need of serious attention.

    BUILDING HISTORY

    Before I can specify historically appropriate treatments, I need to don my consultant’s cap and dig into the history of a building to best understand its evolution. Developing the background story will typically answer questions and fill in the blanks when examining traditional building systems. An 1890 newspaper clipping held by the Cambridge Historic Commission re- ports that “[t]he stately home of Mr. Abbot, with its walled-in grounds, on the site of the old Arsenal, promises to be the most costly private dwelling in the city.” An examination of records held by the Massachusetts Historical Commission and from the Library of Congress’ Historic American Buildings Survey reveals that the firm of Longfellow, Alden & Harlow designed the Richardsonian Romanesque portion of the building and that Norcross Brothers Contractors and Builders was the builder of record.

    Alexander Wadsworth Longfellow Jr. (of Longfellow, Alden & Harlow) was the nephew of the famous poet Henry Wadsworth Longfellow and an important figure in U.S. architectural history. After graduating from Harvard University in 1876, he studied architecture at the Massachusetts Institute of Technology and the École des Beaux-Arts in Paris, after which he worked as a senior draftsman in Henry Hobson Richardson’s office. After Richardson’s death in 1886, Longfellow partnered with Frank Ellis Alden and Alfred Branch Harlow to found the firm of Longfellow, Alden & Harlow. With offices in Boston and Pittsburgh, the firm designed many important buildings, including the Carnegie Library in Pittsburgh and the City Hall in Cambridge.

    Norcross Brothers Contractors and Builders was a prominent 19th century American construction company, especially noted for its work, mostly in stone, for the architectural firms of Henry Hobson Richardson and McKim, Mead & White. Much of the value of the Norcross Brothers to architectural firms derived from Orlando Norcross’ engineering skill. Although largely self- taught, he had developed the skills needed to solve the vast engineering problems brought to him by his clients. For example, the size of the dome at the Rhode Island Capitol was expanded very late in the design process, perhaps even after construction had begun, so that it would be larger than the one just completed by Cass Gilbert for the Minnesota Capitol. Norcross was able to execute the new design.

    BUILDING STYLE

    The Edwin Abbot House is an interesting interpretation of the Richardsonian Romanesque style. Whereas the great majority of such buildings feature rusticated, pink Milford granite in an ashlar pattern, trimmed with East Longmeadow brownstone, Longfellow created a unique spin for Mr. Abbot. Although the building is trimmed with brownstone, the field of the walls features coursed Weymouth granite of slightly varying heights. The motif of orange, brown and golden hues of the stone is continued in the brick wall surrounding the property.

    Scaffolding was erected that would make the otherwise dangerous, heavy nature of the work safe and manageable.

    Scaffolding was erected that would make the otherwise dangerous, heavy nature of the work safe and manageable.

    The roof is covered in a flat, square orange-red clay tile. Richardsonian Romanesque buildings are almost exclusively roofed in clay tile; Monson black slate; Granville, N.Y., red slate; or some combination thereof. It should be noted that because their need for stone was outpacing the supply, Norcross Brothers eventually acquired its own quarries in Connecticut, Georgia, Maine, Massachusetts and New York.

    The roof framing system of steel and terra-cotta blocks is relatively rare but makes perfect sense when considered in context with the latest flooring technologies of the era. A network of steel beams was bolted together to form the rafters, hips and ridges of the frame. Across each is welded rows of double angle irons (or inverted T beams). Within these channels, in beds of Portland cement, the terra-cotta block was laid. The tile was then fastened directly to the blocks with steel nails. Because of the ferrous nature of the fasteners, the normal passage of moisture vapor caused the nails to rust and expand slightly, anchoring them securely in place. Whether this element of the design was intentional or simply fortunate happenstance, the result made for a long-lasting roof.

    What doesn’t last forever in traditional slate and clay tile roofing systems is the sheet-metal flashing assemblies. Over the years, there must have been numerous failures, which led to the decision to remove the clay tiles from the broad fields of the roof and replace them with red asphalt shingles in the 1980s. Confronted with the dilemma of securing the shingles to the terra-cotta substrate, a decision was made to sheathe the roof with plywood. Holes were punched through the blocks and toggles used to fasten the plywood to the roof. In an area where the asphalt shingles were removed, more than 50 percent of the plywood exhibited varying degrees of rot caused by the normal passage of vapor from the interior spaces.

    Fortunately, the turrets had survived the renovations from 30 years before. A conical turret in the rear and an eight-sided hip-roofed turret on the north side needed only repairs which, while extensive, did not require addressing issues with the substrate. The 16-sided turret on the primary façade of the building was in poor condition. Over the years, prior “repairs” included the use of non-matching tiles, red roofing cement, tar, caulk and even red slate. A scaffold was erected to allow safe, unfettered access to the entire turret and the process of removing the tile began. Care was taken to conserve as many tiles as possible for use in repairing the previously described turrets.

    As the clay-tile roof covering was removed, the materials of the substrate were revealed and conditions were assessed.

    As the clay-tile roof covering was removed, the materials of the substrate were revealed and conditions were assessed.

    The substrate was examined closely and, save for thousands of tiny craters created by the original nails, found to be sound. A new system had to be devised that could be attached to the terra-cotta blocks and allow for the replacement tiles to be securely fastened, as well as resist the damaging forces of escaping moisture vapor. Cement board, comprised of 90 percent Portland cement and ground sand, was fastened to the blocks with ceramic-coated masonry screws. The entire turret was then covered with a self-adhering membrane. The replacement tiles were carefully matched and sourced from a salvage deal- er in Illinois and secured with stain- less-steel fasteners. The flat tiles, no longer manufactured new, are referred to as “Cambridge” tiles for their prevalence on the roofs of great homes and institutional buildings in and around Cambridge.

    CONTEMPORARY UPDATES

    Although I typically advocate for the retainage of all historic fabric when preserving and restoring traditional building systems, there are exceptions. In the case of the Abbot House roof, we encountered “modern” technologies that pointed us toward contemporary means and methods. Rusting steel nails in the terra-cotta block were brilliant for initial installation but seemed ill conceived for a second-go-round. Instead, using non-ferrous fasteners and a new substrate that is impervious to moisture infiltration will guarantee the turret’s new service life for the next 125 years or more.

    ROOF MATERIALS

    Self-adhering Membrane: Grace Ice & Water Shield
    Masonry Anchors: Tapcon
    Cement Board: James Hardie
    Stainless-steel Roofing Nails: Grip Rite
    Replacement Tiles: Renaissance Roofing Inc.

    PHOTOS: Ward Hamilton

    Better Understand Why the Combination of Moisture and Concrete Roof Decks Is Troublesome

    The primary function of a well-built and well-designed roofing system is to prevent water from moving through into the building below it. Yet, as the Rosemont, Ill.-based National Roofing Contractors Association has observed, an increasing number of “good roofs” installed on concrete roof decks have failed in recent years. Blistering, de-bonding and substrate buckling have occurred with no reports of water leakage. Upon investigation, the roofing materials and substrates are found to be wet and deteriorated.

    Wagner Meters offers moisture-detection meters for concrete. The meters are designed to save time and money on a project or job site.

    Wagner Meters offers moisture-detection meters for concrete. The meters are designed to save time and money on a project or job site.

    Why is this? One potential cause is trapped moisture; there are numerous potential sources of trapped moisture in a structure. Let’s examine the moisture source embedded within the concrete roof deck.

    WHY DOES THIS MOISTURE BECOME TRAPPED?

    It often starts with the schedule. In construction, time is money, and faster completion means lower cost to the general contractor and owner. Many construction schedules include the installation of the roof on the critical path because the interior building components and finishes cannot be completed until the roof has been installed. Therefore, to keep the project on schedule, roofers are pressured to install the roof soon after the roof deck has been poured. Adding to the pressure are contracts written so the general contractor receives a mile- stone payment once the roof has been installed and the building has been topped out.

    Historically, roofers wait a minimum of 28 days after the roof deck is poured before starting to install a new roof. This is the concrete industry’s standard time for curing the concrete before testing and evaluating the concrete’s compressive strength. Twenty-eight days has no relation to the dryness of a concrete slab. Regardless, after 28 days the roofer may come under pres- sure from the general contractor to install the roof membrane. The concrete slab’s surface may pass the historic “hot asphalt” or the ASTM D4263 Standard “plastic sheet” test, but the apparently dry surface can be deceptive. Curing is not the same as drying, and significant amounts of water remain within a 28-day-old concrete deck. Depending on the ambient conditions, slab thickness and mixture proportions, the interior of the slab will likely have a relative humidity (RH) well over 90 percent at 28 days.

    FROM WHERE DOES THE WATER COME?

    Upon placing the concrete slab, the batch water goes to several uses. Portland cement reacts with water through the hydration process, creating the glue that holds concrete together. The remaining water held in capillary pores can be lost through evaporation, but evaporation is a slow, diffusion-based process. The diffusion rate of concrete is governed by the size and volume of capillary pores which, in turn, are controlled by the water/cement (w/cm) ratio. The total volume of water that will be lost is controlled by the degree of hydration, which is primarily related to curing and w/cm.

    A 4-inch-thick concrete slab releases about 1 quart of water for each square foot of surface area. If a roof membrane is installed before this water escapes the slab, it can become trapped and collect beneath the roof system. The water does not damage the concrete, but it can migrate into the roofing system—and that’s when problems begin to occur. For instance, moisture that moves into the roofing system can:

    • Reduce thermal performance of the insulation.
    • Cause the insulation, cover board, adhesive or fasteners to lose strength, making the roofing system susceptible to uplift or damage from wind, hail or even foot traffic.
    • Lead to dimensional changes in the substrate, causing buckling and eventually damaging the roof membrane.
    • Allow mold growth.

    A number of factors compound the problem. In buildings where a metal deck is installed, moisture cannot exit the slab through its bottom surface. Instead, the moisture is forced to exit the slab by moving upward. Eliminating one drying surface almost doubles the length of drying time of a concrete slab. The small slots cut in ventilated metal decking have little effect on reducing this drying time.

    Ambient conditions also affect the drying rate of a concrete slab since it readily absorbs and retains moisture. Additional moisture may enter an unprotected roof slab from snow cover, rain or dew. Even overcast days will slow the rate of drying.

    A MODERN-DAY PROBLEM

    Before the introduction of today’s low-VOC roofing materials, historic roof systems didn’t experience as many of these moisture issues. Typically, they were in- stalled onto concrete decks on a continuous layer of hot asphalt adhesive that bonded the insulation to the deck. This low-permeable adhesive acted as a vapor retarder and limited the rate of moisture migrating from the concrete into the roofing assembly. As a result, historic roof systems were somewhat isolated from moisture coming from the concrete slab.

    Many of today’s single-ply roof membranes are not installed with a vapor retarder. Moisture is able to migrate from the concrete slab into the roof materials. Modern insulation boards are often faced with moisture-sensitive paper facers and adhered to substrates with moisture-sensitive adhesives. These moisture-sensitive paper facers and adhesives are causing many of the problems.

    Rene Dupuis of Middleton, Wis.- based Structural Research Inc. recently presented a paper to the Chicago Roofing Contractors Association on the subject. Some of his findings include the following:

    • Due to air-quality requirements, government regulations curtailed the use of solvent-based adhesives because they are high in VOCs. Consequently, manufacturers changed to water-based adhesives because they are lower in VOCs, have low odor, are easy to apply and pro- vide more coverage.
    • There can be several drawbacks to water-based bonding adhesives. One is that they may be moisture sensitive. Moisture and alkaline salts migrating into roof systems from concrete decks can trigger a negative reaction with some water-based adhesives. This reaction can cause the adhesives to revert to a liquid, or it may alter or delay the curing of some foam-based adhesives. Some adhesive manufacturers have recognized these problems and have be- gun reformulating their adhesives to address these drawbacks.
    • Negative reactions also occur when moisture-sensitive paper facers come into contact with moisture. This reaction typically results in decay, mold growth and loss of cohesive strength. Moisture in the roof system may also cause gypsum and wood-fiber-based cover boards to lose cohesive strength.

    Dupuis noted moisture from any source can compromise adhered roof systems with wind uplift when attached to paper insulation or gypsum board. He also said facer research clearly shows paper facers suffer loss of strength as moisture content increases.

    PHOTOS: Wagner Meters

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    Attic Ventilation in Accessory Structures

    Construction Code Requirements for Proper Attic Ventilation Should Not Be Overlooked in Buildings That Don’t Contain Conditioned Space

    The 2015 International Residential Code and International Building Code, published by the International Code Council, include requirements for attic ventilation to help manage temperature and moisture that could accumulate in attic spaces. Although the code requirements are understood to apply to habitable buildings, not everyone understands how the code addresses accessory structures, like workshops, storage buildings, detached garages and other buildings. What’s the answer? The code treats all attic spaces the same, whether the space below the attic is conditioned or not. (A conditioned space is a space that is heated and/or cooled.)

    The 2015 International Residential Code and International Building Code include requirements for attic ventilation to help manage temperature and moisture that could accumulate in attic spaces. Although the code requirements are understood to apply to habitable buildings, not everyone understands the code also addresses accessory structures, like workshops, storage buildings, detached garages and other buildings.

    The 2015 International Residential Code and International Building Code include requirements for attic ventilation to help manage temperature and moisture that could accumulate in attic spaces. Although the code requirements are understood to apply to habitable buildings, not everyone understands the code also addresses accessory structures, like workshops, storage buildings, detached garages and other buildings.


    The administrative provisions of the IRC that set the scope for the code are found in Chapter 1. Section R101.2 and read:

      The provisions of the International Residential Code for One- and Two-family Dwellings shall apply to the construction, alteration, movement, enlargement, replacement, repair, equipment, use and occupancy, location, removal and demolition of detached one- and two-family dwellings and townhouses not more than three stories above grade plane in height with a separate means of egress and their accessory structures not more than three stories above grade plane in height.

    Let’s clear up any confusion about the code. The ventilated attic requirements in the 2015 IRC include the following language in Section R806.1:

      Enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters shall have cross ventilation for each separate space by ventilating openings protected against the entrance of rain or snow.

    An accessory structure is actually defined in the IRC:

      ACCESSORY STRUCTURE. A structure that is accessory to and incidental to that of the dwelling(s) and that is located on the same lot.

    The IBC also includes attic ventilation requirements that are essentially the same as the IRC. Section 101.2 of the 2015 IBC contains this text:

      The provisions of this code shall apply to the construction, alteration, relocation, enlargement, replacement, repair, equipment, use and occupancy, location, maintenance, removal and demolition of every building or structure or any appurtenances connected or attached to such buildings or structures.

    This requirement for ventilated at-tics in accessory structures in the IBC and IRC is mandatory unless the attic is part of the conditioned space and is sealed within the building envelope. Unvented, or sealed, attics allow any ducts located in the attic to be inside the conditioned space, which can have beneficial effects on energy efficiency. For accessory structures, which are typically unheated, that provision does not apply.

    It’s important to note the codes do contain detailed requirements for the design and construction of sealed at-tics to reduce the chance of moisture accumulation in the attic. These requirements have been in the codes for a relatively short time and remain the subject of continued debate at ICC as advocates of sealed attics work to improve the code language in response to concerns about performance issues from the field.

    Traditional construction methods for wood-framed buildings include ventilated attics (with insulation at the ceiling level) as a means of isolating the roof assembly from the heated and cooled space inside the building. Attic ventilation makes sense for a variety of reasons. Allowing outside air into the attic helps equalize the temperature of the attic with outdoor space. This equalization has several benefits, including lower roof deck and roof covering temperatures, which can extend the life of the deck and roof covering. However, it is not just temperature that can be equalized by a properly ventilated attic. Relative humidity differences can also be addressed by vented attics. Moisture from activity in dwelling units including single-family residences and other commercial occupancies can lead to humidity entering the attic space by diffusion or airflow. It is important to ensure moisture is removed or it can remain in the attic and lead to premature deterioration and decay of the structure and corrosion of metal components, including fasteners and connectors.

    In northern climate zones, a ventilated attic can isolate heat flow escaping from the conditioned space and reduce the chance of uneven snow melt, ice dams, and icicle formation on the roof and eaves. Ice damming can lead to all kinds of moisture problems for roof assemblies; it is bad enough that roof assemblies have to deal with moisture coming from inside the attic, but ice damming can allow water to find its way into roof covering assemblies by interrupting the normal water-shedding process. For buildings with conditioned space, the attic can isolate the roof assembly from the heat source but only if there is sufficient ceiling insulation, properly installed over the top of the wall assemblies to form a continuous envelope. Failure to ensure continuity in the thermal envelope is a recipe for disaster in parts of the country where snow can accumulate on the roof.

    Accessory buildings, like workshops, that occasionally may be heated with space heaters or other sources are less likely to have insulation to block heat flow to the roof, which can result in ice damming. Ventilating the attic can prevent this phenomenon.

    Accessory buildings, like workshops, that occasionally may be heated with space heaters or other sources are less likely to have insulation to block heat flow to the roof, which can result in ice damming. Ventilating the attic can prevent this phenomenon.


    For unheated buildings in the north, ice damming is less likely to occur, unless the structure is occasionally heated. Accessory buildings, like workshops, that might be heated from time to time with space heaters or other sources are less likely to have insulation to block heat flow to the roof. In these situations, a little heat can go a long way toward melting snow on the roof.

    While the ice damming and related performance problems are a real concern even for accessory structures, it is the removal of humidity via convective airflow in the attic space that is the benefit of ventilated attics in accessory structures. We know that moisture will find its way into buildings. Providing a way for it to escape is a necessity, especially for enclosed areas like attics.

    There are many types of accessory structures, and some will include conditioned space. Depending on the use of the structure, moisture accumulation within the building will vary. For residential dwelling units, building scientists understand the normal moisture drive arising from occupancy. Cooking, laundering and showering all contribute moisture to the interior environment.

    The IRC and IBC include requirements for the net-free vent area of intake (lower) and exhaust (upper) vents and also require the vents be installed in accordance with the vent manufacturer’s installation instructions. The amount of required vent area is reduced when a balanced system is installed; most ventilation product manufacturers recommend a balance between intake and exhaust. The IRC recommends that balanced systems include intake vents with between 50 to 60 percent of the total vent area to reduce the chance of negative pressure in the attic system, which can draw conditioned air and moisture from conditioned space within the building. This is less of an issue for non-habitable spaces from an energy-efficiency perspective, but moisture accumulation is a concern in all structures.

    PHOTOS: Lomanco Vents

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    After Years of Roof Leaks, a Laboratory That Produces Theatrical Equipment and Software Undergoes a Complex Reroofing

    Founded in 1910, Rosco Laboratories is a multi-national producer of equipment, software and products for the theatrical, film, and television industries and architectural environment. As with every aging flat roofing system, water leakage was becoming a recurring problem at Rosco’s Stamford, Conn., facility. The severity of the leakage was further exacerbated by the lack of roof drainage (only two roof drains serviced the entire building) and poor deck slope conditions (less than 1/16 inch per foot).

    The gypsum decking was cut out within the limits of the entire framing “bay” and infilled with galvanized metal decking. The longitudinal deck panel edge was seated atop the horizontal leg of the bulb-tee section (visible in the center of the photograph) and mechanically fastened using self-tapping screws. The ends were supported by the steel purlins. The underside of the decking was prepainted to match the ceiling finish. Supplemental structural support consisting of strips of 14-gauge galvanized sheet metal were attached to the bottom of each bulb-tee section contiguous to the repair to provide additional support for the adjacent gypsum roof decking segment.

    The gypsum decking was cut out within the limits of the entire framing “bay” and infilled with galvanized metal decking. The longitudinal deck panel edge was seated atop the horizontal leg of the bulb-tee section (visible in the center of the photograph) and mechanically fastened using self-tapping screws. The ends were supported by the steel purlins. The underside of the decking was prepainted to match the ceiling finish. Supplemental structural support consisting of strips of 14-gauge galvanized sheet metal were attached to the bottom of each bulb-tee section contiguous to the repair to provide additional support for the adjacent gypsum roof decking segment.


    Rosco representatives employed traditional methods to control and/or collect the moisture within the building by use of several water diverters. This technique was effective but Rosco representatives soon recognized this was not a viable long term solution as the physical integrity of the roof structure (deck) became a principal concern to the safety of the building occupants.

    The Fisher Group LLC, an Oxford, Conn.-based building envelope consulting firm was retained by Rosco in March 2009 to survey the existing site conditions and determine the need for roofing replacement. The existing roofing construction, which consisted of a conventional two-ply, smooth-surfaced BUR with aluminized coating, exhibited numerous deficiencies (most notably severe alligatoring) and was deemed unserviceable. Construction documents, including drawings and specifications and a project phasing plan were developed by Fisher Group to address the planned roof replacement.

    Bid proposals were solicited from prequalified contractors in June 2010, and F.J. Dahill Co. Inc., New Haven, Conn., was awarded the contract on the basis of lowest bid.

    Existing Conditions

    The building basically consists of a 1-story steel-framed structure constructed in the 1970s. It is a simple “box”-style configuration, which is conducive to manufacturing.

    In conjunction with design services, destructive test cuts were made by Fisher Group in several roof sections as necessary to verify the existing roofing composition, insulation substrate, moisture entrapment, and substrate/deck construction. A total of four distinct “layers” of roofing were encountered at each test cut. The existing roofing construction consisted of alternating layers of smooth- and gravel-surfaced, multi-ply felt and bitumen built-up roofing. The bitumen contained throughout the construction was fortunately asphalt-based. Succeeding layers of roofing were spot mopped or fully mopped to the preceding layer (system). The combined weight of the roofing construction was estimated to be upwards of 20 to 22 pounds per square foot when considering the moisture content. This is excessive weight.

    The roof insulation panels were set into ribbons of low-rise polyurethane foam insulation adhesive. The adhesive was applied in a continuous serpentine bead, spaced 6 inches on-center throughout the field of the roof.

    The roof insulation panels were set into ribbons of low-rise polyurethane foam insulation adhesive. The adhesive was applied in a continuous serpentine bead, spaced 6 inches on-center throughout the field of the roof.


    It is interesting to note that a minimal amount of roof insulation was present in the existing construction. Insulation was limited to a single layer of 1/2-inch-thick fiberboard. Additional insulation would need to be provided as part of the replacement roofing construction to increase the roof’s thermal performance and comply with the prescriptive requirements of the Connecticut State Energy Conservation Construction Code.

    The structural substrate, or decking, is conventional in nature, comprised of poured gypsum roof decking. The roof decking incorporates 1/2-inch gypsum formboard loose laid between steel bulb-tee supports spaced about 32 inches on-center. The poured gypsum roof decking in this instance was utilized as the structural substrate and for insulating purposes. Poured gypsum roof decking has a minimal insulating value of perhaps R-2 to R-3, which is obviously considered to be minimal by present standards.

    A representative number of bulk material samples were obtained by Fisher Group from the existing roofing construction as necessary to determine the material composition. The sampling included field membrane roofing plies, coatings and cements, and associated roof penetration and perimeter flashings. Laboratory analysis revealed that the second, third and, in some instances, fourth roofing “layers” (field membrane plies) contained varying amounts—5 to 10 percent—of asbestos (chrysotile) which would necessitate full abatement of the roofing construction.

    PHOTOS: The Fisher Group LLC

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