Retrofit MBI System for Insulating Metal Buildings

rFOIL introduces the Retrofit MBI System for insulating metal buildings. According to the company, the patented clip and pin system combined with rFOIL’s reliable insulation provides a cost-effective and energy-efficient way to insulate all types of metal buildings. The MBI Retrofit clip is installed to the bottom of the exposed roof purlins and inside the wall girts. The system allows for the addition of insulation mass. The Retrofit MBI System is lightweight, easy to handle and easy to install. With its unique attachment system, it can be quickly installed with minimal interruption to the facility’s operation.

rFoil insulation is a single or double layer of polyethylene bubbles bonded to and sandwiched between a highly reflective surface and a white polyethylene sheet. According to them manufacturer, rFOIL is recognized for its thermal performance, easy installations, versatility and environmental friendliness and offers a number of advantages over traditional insulations. Its unique construction is specially designed to reduce radiant heat gain or loss in residential, commercial, post-frame, metal frame and HVAC applications. 

For more information, visit https://www.rfoil.com.

Tapered Insulation Can Prevent Ponding on Low-Slope Roofs

The primary and most important function of a roof membrane in a low-slope roof system is to provide weatherproofing by keeping the rainwater from entering the roof assembly. Ponding water poses the greatest risk to a roofing membrane, since it not only shortens its service life, but can lead to more serious life safety concerns when loads and deflections exceed the designed conditions. This could lead to a roof collapse. From an aesthetics standpoint, areas on roofs with a prevalence for ponding are susceptible to unsightly bacterial and algae growth as well as accumulation of dirt. Given the large footprint of low-slope roofs on typical commercial buildings, managing rainwater timely and effectively is an important design consideration in new roof design as well as roof replacements on existing buildings. In addition, the model building codes include requirements for minimum drainage slope and identify ponding instability as a design consideration for rain loads.

Tapered insulation systems are an integral part of roof system design and can help reduce or eliminate the amount of ponding water on the roof when the roof deck does not provide adequate slope to drain. The popularity of tapered insulation has grown as more designers and roofing professionals understand the importance of positive drainage in good roofing practice. Because of its wide use in low-slope roofing application, tapered polyiso insulation systems offer a number of benefits in addition to providing positive drainage: high R-value, versatility and customization to accommodate project-by-project complexity as well as ease of installation. This article highlights the key considerations for tapered insulation systems.

Slope and Drainage Requirements in Building Codes

The model building codes require that commercial roofs be sloped to achieve a positive drainage of rainwater to drains, scuppers, and gutters. The term “positive roof drainage” is defined in the 2018 International Building Code (IBC) as “the drainage condition in which consideration has been made for all loading deflection of the roof deck, and additional slope has been provided to ensure drainage of the roof within 48 hours of precipitation.” The 2018 IBC indicates a minimum design 1/4:12 units slope requirement for membrane roof systems, and minimum slope of 1/8 inch per foot for coal tar pitch roofs. New construction must comply with the minimum slope requirements in IBC Section 1507. Roof replacement or roof re-cover applications of existing low-slope roof coverings that provide positive roof drainage are exempt from the minimum prescriptive1/4:12 units slope requirement.

Roof drains are part of an approved storm drainage system and function to divert water off and away from the building. Roof drainage systems in new construction must comply with provisions in Section 1502 of the 2018 IBC and Section 1106 and 1108 of the International Plumbing Code (IPC) for primary and secondary (emergency overflow) drains or scuppers. Roof replacement and re-cover applications on existing low-slope roofs that provide positive roof drainage are exempt from requirements for secondary drains or scuppers. It is important to note that secondary drainage systems or scuppers in place on existing buildings cannot be removed unless they are replaced by secondary drains or scuppers designed and installed in accordance with the IBC.

When reviewing the options available for achieving the required slope in a roof system, designers have a number of choices. According to the National Roofing Contractors Association (NRCA) (see “The NRCA Roofing Manual: Membrane Roof Systems: 2019”) the slope can be achieved by: sloping the structural framing or deck; designing a tapered insulation system; using an insulating fill that can be sloped to drain; properly designing the location of roof drains, scuppers and gutters; or a combination of the above.

Design Considerations For Tapered Insulation Systems

Proper design and installation are critical to the effective performance of tapered polyiso insulation systems, and this is true for any product or system. Tapered polyiso is manufactured in 4-foot-by-4-foot or 4-foot-by-8-foot panels that change thicknesses over the 4-foot distance from the low edge to the high edge on the opposing sides of the panel. The standard slopes for tapered insulation are 1/8 inch, 1/4 inch and 1/2 inch per foot to accommodate specific project requirements. However, tapered insulation panels with slopes as low as 1/16 inch and other alternative slopes (3/16 inch and 3/8 inch per foot) can be specially ordered to accommodate unique field conditions. The minimum manufactured thickness of tapered polyiso insulation board at its low edge is 1/2 inch and the maximum thickness at the high edge is 4-1/2 inches.

The design of the tapered insulation system will be governed by the footprint and complexity of the roof under consideration, slope of the roof deck, presence and configuration of roof drains (primary and secondary), scuppers, gutter or drip edges. In addition, roof structures, height of parapet walls, expansion joints, curbs and through-wall flashings and any other elements that may obstruct water management also needs to be considered in the design phase. The tapered insulation system will be lowest at internal drains, scuppers, gutters and drip edges, and will slope upwards away from these features.

Keeping in mind that the primary goal of a tapered insulation system is to most effectively move water to the specified drainage points. A two-way (two directional slope) or four-way (four directional slope) system are the most common designs. A two-way tapered insulation system is commonly used on roofs where multiple drains are in straight lines. In this scenario, there is a continuous low-point between the drains and it often extends to the parapet walls. Crickets are installed in between the drains and between the building or parapet walls and the drains. (See Figure 1a.)

A four-way tapered insulation system is the most effective way to move water off the roof, and this approach is highly recommended by industry professionals. In this scenario with a drain located in the center, water is drained from the higher perimeter edges on all four sides. (See Figure 1b.) Variations of two-way and four-way systems exist to accommodate complexities in the field. In addition to two-way and four-way systems, one directional slope and three directional slope tapered systems can be used to effectively move water to gutters, drip edges and scuppers.

Keeping in mind that a tapered system is more expensive than a roof system constructed with standard flat insulation only, the tapered design is often a target for “value engineering.” Value engineering can compromise the drainage intent of the design professional, architect or roof consultant for the purpose of lowering the installed cost of the roof system. Value engineering may change the specified slope or redesign the configuration of the tapered panels. In the end, the building owner may pay for a tapered insulation system that does not effectively drain water from the roof as intended by the original design. This will likely result in higher long-term costs for roof maintenance and premature roof system failure.

A typical tapered insulation system will incorporate flat polyiso board stock (referred to as “fill panels” or “tapered fill panels”) beneath continuing, repeating tapered panels. The tapered panels can be a single panel (or “one panel repeat”) system, meaning that the taper is provided by a single repeating panel in conjunction with fill panels. (See Figure 2a.) Non-typical designs can feature up to an eight-panel (or “eight panel repeat”) system with eight tapered panels making up the sloped section prior to incorporating the first fill panels. An example of “four panel repeat” system with 1-inch and 2-inch fill panels and 1/16 inch per foot slope is provided in Figure 2b.

Finally, crickets are an integral part of a tapered insulation system and are commonly used in two-way systems. Crickets can divert water toward drains and away from curbs, perimeter walls, and roof valleys. The two factors that must be considered in the design and installation of crickets are slope and configuration. The general “rule of thumb” is that for a full diamond cricket the total width should be between 1/3 to 1/2 of the total width. The wider the design of the cricket, the more you utilize the slope in the field of the roof, which improves the drainage efficiency.

Crickets typically have diamond or half-diamond shapes. (See Figures 3a and 3b.) However, kite-shaped and snub nose crickets can also be configured to accommodate specific roof designs. To keep water from remaining on the cricket surface, the design needs to have a sufficient slope (generally, twice the slope in the adjacent field of the roof). NRCA provides guidance regarding cricket geometry (see “The NRCA Roofing Manual: Membrane Roof Systems: 2019”).

Tapered insulation systems offer a cost-effective solution to achieving positive slope and improved drainage in new roof systems and roof replacement applications. An adequate rainwater management strategy that includes both proper drainage and elimination of ponding water is critical to the long-term performance and durability of a roof system. In addition, proper design, detailing, and installation of products must be an integral part of a tapered roof system design. For more information, consult with a polyiso insulation manufacturer who provide guidance, design assistance, and technical information regarding tapered insulation systems. In addition, the Polyisocyanurate Insulation Manufacturers Association (PIMA) publishes technical bulletins to help navigate the process of designing a tapered system. PIMA’s Technical Bulletin #108 on Tapered Insulation Systems can be found at www.polyiso.org/resource/resmgr/Tech_Bulletins/tb108_Mar2017.pdf.

About the author: Marcin Pazera, Ph.D., is the Technical Director for Polyisocyanurate Insulation Manufacturers Association (PIMA). He coordinates all technical-related activities at PIMA and serves as the primary technical liaison to organizations involved in the development of building standards. For more information, visit www.polyiso.org.

Improve Commercial Roof Performance With Staggered Insulation Layers

Photo: Hunter Panels

Selecting the right components for a project can dramatically improve the performance and longevity of the overall building. In a commercial roofing project, the chosen insulation and the installation technique are critical to a building’s resilience and thermal efficiency.

From a physics standpoint, energy flows from a region of high to low potential (from warm to cold). Therefore, a significant amount of heat can leave a building through an inadequately insulated roof assembly during heating season (winter) and enter a building through an inadequately insulated roof assembly during cooling season (summer). A building with an under-insulated roof assembly may require more energy to compensate for these heat gains and losses.

The benefits of installing multiple, staggered layers of rigid board insulation have been well known for years. Industry authorities, including National Roofing Contractors Association (NRCA), Oak Ridge National Laboratory (ORNL), Canadian Roofing Contractor Association (CRCA) and International Institute of Building Enclosure Consultants (IIBEC), formerly RCI, Inc., have recognized these benefits; and contractors, designers and specifiers have followed the roofing industry’s long-standing recommendation for the installation of staggered insulation layers.

Using the optimal roof insulation product also will impact performance. Polyiso insulation offers key advantages in meeting stricter building standards and improving energy efficiency. Polyiso has a high design R-value compared to XPS, EPS, and mineral wool board. Lightweight and easy to trim, polyiso can be layered to reach the desired R-values without being cumbersome to install.

Why Are Multiple, Staggered Layers of Insulation Important?

In 2015, the International Energy Conservation Code (IECC) increased the R-value requirements for the opaque thermal envelope in many climate zones across the United States. As a practical matter, most roofs will require two or more layers of insulation to meet the local energy code requirements. In the 2018 version, the IECC was updated with specific installation requirements for continuous roof insulation. The 2018 IECC explicitly calls for continuous insulation board to be installed “in not less than 2 layers and the edge joints between each layer of insulation shall be staggered” (Section C402.2.1 Roof assembly). 

Figure 1. Multiple, staggered layers of insulation can minimize air infiltration and reduce or prevent condensation in the roof system.

Staggering the joints of continuous insulation layers offer a number of benefits:

· Increased thermal performance/reduced thermal loss: The staggered joints on multiple layers of insulation offset gaps where heat could flow between adjacent boards. The staggered approach to installing insulation reduces thermal bridging in the roof assembly. A fact sheet on roof insulation published by Johns Manville (RS-7386) notes that as much as 8 percent of the thermal efficiency of insulation can be lost through the joints and exposed fasteners of installations that use only a single layer of insulation.

· Air intrusion: When conditioned air enters the building envelope, often because of pressure gradients, it carries moisture into the roofing system. This moisture will undermine optimal performance. A peer-reviewed study on air intrusion impacts in seam-fastened mechanically attached roofing systems showed that air intrusion was minimized by nearly 60 percent when the insulation joints were staggered between multiple layers of insulation. (See “Air Intrusion Impacts in Seam-Fastened, Mechanically Attached Roofing Systems,” by By Suda Molleti, PEng; Bas Baskaran, PEng; and Pascal Beaulieu, www.iibec.org.)

Additionally, by limiting the flow of air and moisture through a roof system, staggered layers of insulation in a roof assembly can reduce and/or prevent condensation. The condensed moisture if allowed to remain and accumulate in the system can damage the substrate and potentially shorten the service life of a roof. A properly insulated roof can also prevent the onset of condensation by effectively managing the dew-point within the roof assembly. 

· Resilient roof assemblies: Staggered joints can reduce the stress put on a single insulation layer and distribute that stress more evenly over multiple, thinner insulation joints. For example, in an adhered roof system, the installation of multiple layers of insulation can minimize the potential for membrane splitting. In this system, the upper layer(s) of insulation can protect the membrane from potential physical damage caused by fasteners that are used to attach the bottom layer of insulation to the roof deck.

· Ponding water: Roof slope is often created through the use of tapered insulation systems. These systems offer an opportunity to stagger the joints by offsetting insulation layers and improve overall energy performance of a system. If the added insulation layer is tapered, the slope provided can improve drainage performance of the roof. Rainwater that does not drain and remains standing, collects dirt and debris that can damage or accelerate erosion of roof covering. Integrating tapered polyiso system with staggered joints into a roof’s design will not only improve the thermal performance but also can improve drainage and thus overall longevity of the system.

· Puncture resistance: Roof cover boards are commonly installed to provide a suitable substrate for membrane attachment as well as protect the roof assembly from puncture and foot traffic. When using products like polyiso high-density roof cover boards, the joints should also be staggered with the underlying roof insulation. This ensures the benefits discussed above are preserved in systems utilizing cover boards.

Installation Best Practices Are Keys For Success

A properly designed roof system that utilizes high-performance polyiso insulation products is a strong foundation (or cover) for energy-efficient and sustainable construction. However, the designed performance can only be achieved through proper installation. Implementing industry best practices such as the installation of multiple layers with staggered joints will optimize energy efficiency of the system and will help ensure that the roof system performs during its service life.  

To learn more about the benefits and uses of polyiso insulation,please visit the Polyisocyanurate Insulation Manufacturers Association website at www.polyiso.org.

About the author: Marcin Pazera, Ph.D., is the Technical Director for Polyisocyanurate Insulation Manufacturers Association (PIMA). He coordinates all technical-related activities at PIMA and serves as the primary technical liaison to organizations involved in the development of building standards. For more information, visit www.polyiso.org.

Insulation Adhesive Canisters Enhance Rooftop Productivity

Each OlyBond500 canister set is self-contained, and comes with a 25-foot application hose, gun assembly, six mix tips, three extension tubes as well as a disposable wrench for securing the hoses to the canisters. The unique applicator “gun” includes a locking trigger designed to prevent accidental adhesive discharges on the roof. The 17-inch long extension tubes enable contractors to stand upright during application for better ergonomics and less fatigue.

“On almost a daily basis we’re hearing from contractors from across the country that OlyBond500 Canisters provide a highly labor efficient method of installing insulation adhesives,” said Adam Cincotta, adhesives business unit leader for OMG Roofing Products. “They love the fact that these systems do not require any extra or specialized equipment, rooftop power or highly skilled labor. Just connect the hoses and go!”

When compared to other canister based low-rise foaming adhesives, OlyBond500 Canisters can provide up to 20 percent more coverage and up to 35 squares per set, depending on the conditions and insulation used, according to the manufacturer. In addition, OlyBond500 Canisters enable users to spatter the adhesive for use with fleece backed membranes.

“In addition to productivity gains, canisters do not require highly skilled applicators, so contractors can assign skilled labors to work on other things rather than applying adhesive,” said Cincotta. “I expect to see more contractors adopt this strategy as the labor shortage continues.”

For more information, visit www.OMGRoofing.com.

Designing Thermally Efficient Roof Systems

Photo 1. Designing and installing thermal insulation in two layers with offset and staggered joints prevents vertical heat loss through the insulation butt joints. Images: Hutchinson Design Group Ltd.

“Energy efficiency,” “energy conservation,” and “reduction of energy use” are terms that are often used interchangeably, but do they mean the same thing? Let’s look at some definitions courtesy of Messrs. Merriam and Webster, along with my interpretation and comment:

· Energy efficiency: Preventing the wasteful use of a particular resource. (Funny thing, though — when you type in “energy efficiency” in search engines, you sometimes get the definition for “energy conservation.”

· Energy conservation: The total energy of an isolated system remains constant irrespective of whatever internal changes may take place, with energy disappearing in one form reappearing in another. (Think internal condensation due to air leaking, reducing thermal R-value of the system.)

· Reduction: The action of making a specific item (in this case energy use) smaller or less in amount. (Think cost savings.)

· Conservation: Prevention of the wasteful use of a resource.

So, looking at this article’s title, what does “designing a thermally efficient roof system” imply?

Photo 2. Rigid insulation is often cut short of penetrations, in this case the roof curb. To prevent heat loss around the perimeter of the curb, the void has been sprayed with spray polyurethane foam insulation. Open joints in the insulation have also been filled with spray foam insulation. Note too, the vapor retarder beyond the insulation.

I conducted an informal survey of architects, building managers, roof consultants and building owners in Chicago, and they revealed that the goals of a thermally efficient roof system include:

  • Ensuring energy efficiency, thus preventing the wasteful use of energy.
  • Reducing energy use, thus conserving a resource.
  • Being energy conservative so that outside forces do not reduce the energy-saving capabilities of the roof system.

Unfortunately, I would hazard a guess and say that most new roof systems being designed do not achieve energy conservation.

Why is this important? The past decade has seen the world building committee strive to ensure the energy efficiency of our built environment.

A building’s roof is often the most effective part of the envelope in conserving energy. The roof system, if designed properly, can mitigate energy loss or gain and allow the building’s mechanical systems to function properly for occupant comfort.

Photo 3. Rigid insulation is often not tight to perimeter walls or roof edges. Here the roofing crew is spraying polyurethane foam insulation into the void to seal it from air and heat transfer. Once the foam rises it will be trimmed flush with the surface of the insulation.

Energy conservation is increasingly being viewed as an important performance objective for governmental, educational, commercial and industrial construction. Interest in the conservation of energy is high and is being actively discussed at all levels of the building industry, including federal and local governments; bodies that govern codes and standards; and trade organizations.

As with many systems, it is the details that are the difference between success and failure on the roof. This article will be based on the author’s 35 years of roof system design and in-field empirical experience and will review key design elements in the detailing of energy-conserving roof systems. Best design and detail practices for roofing to achieve energy conservation will be delineated, in-field examples reviewed and details provided.  

Advocacy for Improvement

In the past decade, American codes and standard associations have increased the required thermal values every updating cycle. They have realized the importance of energy conservation and the value of an effective thermal layer at the roof plane. They have done this by prescribing thermal R-values by various climatic zones defined by the American Society of Heating and Air-Conditioning Engineers, now better known by its acronym ASHRAE. Additionally, two layers of insulation with offset joints are now prescribed in the IECC (International Energy Conservation Code). Furthermore, the American Institute of Architects (AIA) has also realized the importance of conserving energy and defined an energy conservation goal called the 2030 Challenge, in which they challenge architects, owners and builders to achieve “zero energy” consuming buildings by 2030.

These codes, standards and laudable goals have gone a long way to improving energy conservation, but they are short on the details that are needed to achieve the vision.

Energy Conservation Is More Than Insulation

Roofs are systems and act as a whole. Thus, a holistic view of the system needs to be undertaken to achieve a greater good. Roof system parameters such as the following need to be considered:

  • Air and/or vapor barriers and their transitions at walls, penetrations and various roof edges.
  • Multiple layers of insulation with offset joints.
  • Preventing open voids in the thermal layers at perimeters and penetrations.
  • Protection of the thermal layer from physical damage above and warm moist air from below.
Photo 4. The mechanical fasteners below the roof membrane used to secure the insulation conduct heat through them to the fastening plate. The resultant heat loss can be observed in heavy frost and snowfall.

Air intrusion into the roof system from the interior can have extremely detrimental consequences. In fact, Oak Ridge National Laboratory research has found that air leakage is the most important aspect in reducing energy consumption. Interior air is most often conditioned, and when it moves into a roof system, especially in the northern two-thirds of the country where the potential for condensation exists, the results can include wet insulation, deteriorating insulation facers, mold growth and rendering the roof system vulnerable to wind uplift. Preventing air intrusion into the roof system from the interior of the building needs to be considered in the design when energy efficiency is a goal. Thus, vapor retarders should be considered for many reasons, as they add quality and resiliency to the roof system (refer to my September/October 2014 Roofing article, “Vapor Retarders: You Must Prevent Air and Vapor Transport from a Building’s Interior into the Roof System”). The transition of the roof vapor/air barrier and the wall air barrier should be detailed and the contractors responsible for sealing and terminations noted on the details.

One layer of insulation results in joints that are often open or could open over time, allowing heat to move from the interior to the exterior — a thermal short. Energy high to energy low is a law of physics that can be severe. Thus, the International Code Council now prescribes two layers of insulation with offset joints. (See Photo 1.)

When rigid insulation is cut to conform around penetrations, roof edges and rooftop items, the cuts in the insulation are often rough. This results in voids, often from the top surface of the roof down to the roof deck. With the penetration at the roof deck also being rough, heat loss can be substantial. Thus, we specify and require that these gaps be filled with spray foam insulation. (See Photos 2 and 3.)

Insulation Material Characteristics and Energy Conservation

In addition to the system components’ influence on energy loss, the insulation material characteristics should also be considered. The main insulation type in the United States is polyisocyanurate. Specifiers need to know the various material characteristics in order to specify the correct material. Characteristics to consider are:

Photo 5. Heat loss through the single layer insulation and the mechanical fasteners was so great that it melted the snow, and when temperatures dropped to well below freezing, the melted snow froze. This is a great visual to understand the high loss of heat through mechanical fasteners.
  • Density: 18, 20, 22 or 25 psi; nominal or minimum.
  • Facer type: Fiber reinforced paper or coated fiberglass.
  • Dimensional stability: Will the material change with influences from moisture, heat or foot traffic.
  • Thermal R-value.

In Europe, a popular insulation is mineral wool, which is high in fire resistance, but as with polyisocyanurate, knowledge of physical characteristic is required:

  • Density: If you don’t specify the density of the insulation board, you get 18 psi nominal. Options include 18, 20 and 25 psi; the higher number is more dimensionally stable. We specify 25 psi minimum.
  • Protection required: Cover board or integral cover board.
  • Thermal R-value.

Protecting the Thermal Layer

It is not uncommon for unknowledgeable roof system designers or builders looking to reduce costs to omit or remove the cover board. The cover board, in addition to providing an enhanced surface for the roof cover adhesion, provides a protective layer on the top of the insulation, preventing physical damage to the insulation from construction activities, owner foot traffic and acts of God.

The underside of the thermal layers should be protected as well from the effects of interior building air infiltration. An effective air barrier or vapor retarder, in which all the penetrations, terminations, transitions and material laps are detailed and sealed, performs this feat. If a fire rating is required, the use of gypsum and gypsum-based boards on roof decks such as steel, wood, cementitious wood fiber can help achieve the rating required.

Insulation Attachment and Energy Efficiency

The method in which the insulation is attached to the roof deck can influence the energy-saving potential of the roof system in a major way. This fact is just not acknowledged, as I see some mechanically attached systems being described as energy efficient when they are far from it. Attaching the insulation with asphalt and/or full cover spray polyurethane adhesive can — when properly installed — provide a nearly monolithic thermal layer from roof deck to roof membrane as intended by the codes.

Figure 1. Roof details should be drawn large with all components delineated. Air and vapor retarders should be clearly shown and noted and any special instructions called out. Project-specific roof assembly details go a long way to moving toward ensuring energy conservation is achieved. Here the air and vapor retarder are highlighted and definitively delineated. Voids at perimeters are called out to be filled with spray foam and methods of attachment are noted.

Another very popular method of attaching insulation to the roof deck and each other is the use of bead polyurethane foam adhesive. The beads are typically applied at 6 inches (15.24 cm), 8 inches (20.32 cm), 9 inches (22.86 cm) or 12 inches (30.48 cm).

The insulation needs to be compressed into the beads and weighted to ensure the board does not rise up off the foam. Even when well compressed and installed, there will be a ±3/16-inch void between the compressed beads, as full compression of the adhesive is not possible. This void allows air transport, which can be very detrimental if the air is laden with moisture in cold regions. The linear void below the insulation also interrupts the vertical thermal insulation section.

The most detrimental method of insulation attachment in regard to energy loss is when the insulation is mechanically fastened with the fasteners below the roof cover. Thermal bridging takes place from the conditioned interior to the exterior along the steel fastener. This can readily be observed on roofs with heavy frost and light snowfall, as the metal stress plates below the roof cover transfer heat from the interior to the membrane, which in turn melts the frost or snow above. (See Photo 4.)

The thermal values of roofs are compromised even more when a mechanically attached roof cover is installed. The volume of mechanical fasteners increases, as does the heat loss, which is not insignificant. Singh, Gulati, Srinivasan, and Bhandari in their study “Three-Dimensional Heat Transfer Analysis of Metal Fasteners in Roofing Assemblies”found an effective drop in thermal value of up to 48 percent when mechanical fasteners are used to attach roof covers. (See Photo 5). This research would suggest that for these types of roof systems, in order to meet the code-required effective thermal R-value, the designer needs to increase the required thermal R-value by 50 percent.

Recommendations to Increase Energy Savings

Code and standard bodies as well as governments around the world all agree that energy conservation is a laudable goal. Energy loss through the roof can be substantial, and an obvious location to focus on to prevent energy loss and thus create energy savings. The thermal layer works 24 hours a day, 7 days a week, 52 weeks a year. Compromises in the thermal layer will affect the performance of the insulation and decrease energy savings for years to come. Attention to installation methods and detailing transitions at roof edges, penetrations, walls and drains needs to be given in order to optimize the energy conservation potential of the roof system.

Based on empirical field observation of roof installations and forensic investigations, the following recommendations are made to increase the energy-saving potential of roof systems.

  • Vapor and air barriers are often required or beneficial and should be specifically detailed at laps, penetrations, terminations and transitions to wall air barriers. (See Figure 1.) Call out on the drawings the contractor responsible for material termination so that this is clearly understood.
  • The thermal layer (consisting of multiple layers of insulation) needs to be continuous without breaks or voids. Seal all voids at penetrations and perimeters with closed cell polyurethane sealant.
  • Design insulation layers to be a minimum of two with offset joints.
  • Select quality insulation materials. For polyisocyanurate, that would mean coated fiberglass facers. For mineral wool, that would mean high density.
  • Attach insulation layers to the roof deck in a manner to eliminate thermal breaks. If mechanically fastening the insulation, the fasteners should be covered with another layer of insulation, cover board or both.
  • Design roof covers that do not require mechanical fasteners below the membrane as an attachment method.
  • Protect the thermal layer on top with cover boards and below with appropriate air and vapor barriers.

Saving limited fossil fuels and reducing carbon emissions is a worldwide goal. Designing and installing roof systems with a well thought out, detailed and executed thermal layer will move the building industry to a higher plane. Are you ready for the challenge?

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.

ABC Supply Co. Inc. Acquires the Assets of DRI Supply Co.

Building products distributor ABC Supply Co. Inc. has acquired the assets of DRI Supply Co., a distributor of drywall, roofing and insulation products. ABC will continue to serve customers from the three former DRI locations: 746 Church Hill Road in San Andreas, California; 2300 Cooper Ave. in Merced, California; and 5831 Highway 50 East in Carson City, Nevada.

The acquisition allows ABC Supply to enhance its service in both existing and new markets and strengthen relationships with professional contractors. Current DRI Supply associates will continue to work at the locations, ensuring customers receive seamless access to the products and services they need to run and grow their businesses.

“We’re happy to welcome the DRI Supply team to our ABC family,” said Matt Cooper, vice president of ABC Supply’s West Region. “Contractors will continue to work with the knowledgeable people they’ve come to know, trust and rely on while enjoying access to a wider selection of product options and delivery capabilities.”

For more information, visit www.abcsupply.com.

4 Common Causes of Inadequate Drainage on Low-Slope Roofs

Photo 1. Roof decks with poor slope, drains that are up slope and deck defection can result in excessive ponding. Images: Hutchinson Design Group Ltd.

The stone church in rural Portugal was constructed some 700 years ago. The roofs of the transepts are large stone slabs: 5 feet wide, 10 feet to 12 feet long, and 8 inches thick. How they even made it into place is amazing, but to those like us who think in terms of water, what is even more amazing is the carved-out drainage channels. Moving water off the roof was important to builders 700 years ago in Europe, just as it was to the builders of Machu Picchu and Angkor Wat. Along with many indigenous building methods, the movement of water off roofs and away from buildings is becoming a lost design element.

It is not uncommon to walk upon recently installed roofs and see ponding at gutters, roof drains and across the roof. There are many reasons for this degradation of roof system design, including ignorance. A lack of knowledge by designers, a “roofer or builder will figure it out” mentality, and poor installation procedures can all be to blame.

Ponding water provides visual evidence to the owner that something isn’t quite right, and in some instances, it can result in roof structure collapse. If breaches in the roof membrane exist, standing water can result in excess moisture intrusion. (See Photo 1.) Additionally, water on the roof promotes algae growth that can attack some materials. It also allows for ice to form in winter, creating life safety issues as well as external forces affecting the roof cover.

So, what can you do?

In this article we’ll look at four key conditions on the roof that I see as the most erroneously conceived and installed:

  1. The roof system’s transition to the gutters
  2. Two-way structurally sloped roof decks with roof drains above the low point
  3. Four-way structurally sloped roof decks with drains above the low point
  4. Roof drains on level roof decks with tapered insulation

Accumulated Debris at Gutters

As perhaps you know and will see within this article, there are many things that irk me; one is walking on a new roof and seeing a 3- to 4-foot wide swath of black accumulated dirt and airborne components in front of the gutter. This situation

Photo 2. Owners do not like seeing ponding in front of their gutters, especially when it’s egregious. Proper design and installation would have prevented this problem. Images: Hutchinson Design Group Ltd.

results from restricted water drainage, and it is especially noticeable on reflective roof covers. (See Photo 2.) This restriction of water drainage can be due to several possible factors, including roof edge wood blocking that is too high, insulation that is too low, and the accumulation of roofing material above the slope plane. The roof deck itself can also be set too low.

When designing roof edge gutters, there are key design elements to consider:

  • Wood blocking:In addition to being of appropriate width and anchorage, wood blocking should be sloped to drain, even with sloped roof decks with an elevation 1/4 inch to 3/8 inch below the anticipated roof insulation height. The greatest error I see with most architects is that they do not draw the detail to scale. Insulation is not of the correct thickness, the wood is too big or too small, or it is depicted as one giant block floating atop the wall with no mention of anchorage.
  • Insulation:Please read the ASTM standard for polyisocyanurate and you will learn that the ISO has an allowable dimensional change. Thus, if you specified two layers of 2.25-inch ISO to match three layers of two-by wood blocking, you might be in for a surprise. You might get to the field and see that your two layers of insulation are 3/8 of an inch below the top of the wood, and the manufacturer whom you’ve complained to will pull out the ASTM standard and say, “We are within tolerances.”
  • Material layering:When the roof membrane is taken over the wood (yes you should do this) and sealed to the wall substrate, and the gutter is set in mastic and then stripped in, the accumulated material thickness can exceed 3/8 of an inch. Not much, you say, but on a roof with a 1/4-inch-per-linear-foot slope, that can result in 18 inches of ponding right in front of the gutter. Ouch.

Design recommendations for achieving complete drainage at the roof edge with gutter include:

  • Communicate with the structural engineer.Coordinate with the structural engineer to determine the elevation of the wall (less wood blocking) with the structure and roof deck. If perimeter steel angles attached to the wall rise above the roof deck, discuss with the structural engineer turning the angle downward or changing the angle to one with a vertical leg that doesn’t rise above the roof deck. Angles that rise above the roof deck create a void when

    Photo 3. Even when using tapered insulation and on four-way sloped roof decks, it is advantageous to accentuate the slope into the drain. Here a 1/2-inch-per-foot tapered insulation sump matches up to the tapered insulation with the help if a 1/2-inch tapered edge strip. Images: Hutchinson Design Group Ltd.

    the first layer of insulation is set that is most often not sealed, resulting in a thermal short and a place where dew points can be reached and condensation can occur. If reinforcing paper facers are on the insulation, mold growth can result.

  • Properly detail the wood blocking. I prefer and recommend the use of two layers of wood blocking. First off, do not use treated wood; use untreated Douglas fir. The wood should be at a minimum 8 inches wide (preferably wider) so that the gutter flange can have nail locations back far enough to allow for 3-inch minimum overlap on the stripping-in ply.

Often it is best if the top of the wall is sealed prior to the installation of the wood to prevent air/moisture transport to the wood, and on precast, to prevent the migration of “damp” into the wood. The first layer of wood should be anchored to the structure (wall or framing). While not always required, I prefer to set anchors at 2 feet on center, staggered. This spacing prevents the warping of the wood. The second layer of wood should match the first in width. I suggest that this second layer of blocking be sloped, and placing a continuous shim along the roof side on the first layer will provide the proper slope. The shim width and thickness are dependent on the wood size, but for two-by-ten wood blocking, a shim of 1/2 inch by 1.5 inches will work well. The second layer of wood blocking should be set with joints offset from the lower layer and then screw fastened at 12 inches on center, staggered. Joints on both layers should be scarfed at 45degrees and screwed tight. On your detail, the height of the wood blocking at the interior side above the roof deck should be dimensioned. This will allow contractors to identify height concerns well before the installation of the insulation so adjustments can be made if necessary. I suggest that this distance be 1/4 inch to 3/8 inch below the top surface of the roof insulation or cover board atop the insulation. (See Figure 1.)

  • Make sure the insulation is higher than the wood blocking.We will not discuss insulation types, substrate boards (vapor barriers) and cover boards in this article; please see earlier articles on the topic. In designing the roof edge and discussing/coordinating with the structural engineer, the goal is to have the insulation system: substrate board, vapor retarder, cover board. The thickness should be 3/8 of an inch greater than the interior top corner of the wood blocking. One key item to remember is that spray-and-bead polyurethane adhesive adds 3/8 of an inch thickness per layer. Designing the insulation to be higher than the wood blocking is important, as it compensates for that allowable dimensional change mentioned above, as well as the thickness created by the layers of gutter flange and roofing. The goal is to create a condition in which water will flow over and into the gutter.

Two-Way Structurally Sloped Roof Decks

Often long, narrow roof areas are designed with a two-way structurally sloped roof deck designed to move water from the outer roof edge to a central point. Prudent designers would like the roof drains to be located at the low point of the structurally sloped roof deck. Typically, though, there is a steel beam at the low point, which prevents the installation of the roof drain at the low point. Consequently, the roof drains must be located on the plumbing drawings up slope from the low point. I have tried for years to explain to plumbing engineers that water doesn’t typically flow uphill, but to no avail, so we as the roof system designer have to fix it. How? By moving the low point.

How is this design goal accomplished?

Let’s start with our roof system design for the following example: a new construction project in Chicago (R-30 minimum) with a steel roof deck, two-way structural slope and the low point over a steel beam. The plans call for the drains to be installed 2 feet up slope, and thus they will be more than 1/2 inch above the low point.

The goal will be to move the structural low point to the drain line. With a structural slope, to meet the thermal value we are looking at two layers of 2.6-inch insulation. Run the first layer of 2.6-inch insulation throughout the roof. Then the fun begins: Draw a line down the center of the roof drains. From this centerline, come out 4 feet on each side with a 1/2-inch-per-foot tapered edge board (Q panel, for those who know). The next layer of 2.6-inch insulation abuts the taper. The tapered insulation at the drain line effectively moves the low point to the drains. (See Figure 2.)

Now that the water is being moved to a new low point, it then needs to be moved to the drains. This is accomplished by saddles. (See Figure 3.) Sounds simple enough, but 95 percent of the saddles I see are incorrect, and water ponds on them, over them and along them. This situation leaves, once again, a bad taste in the mouth of the owner, general contractor, construction manager, and architect — even though it’s the designer’s problem. So, I will now, for the first time, reveal my secret developed years ago: The taper of the saddles mustbe twicethe roof deck slope. If the deck slopes 1/4 inch per foot, the saddles must slope at 1/2 inch per foot. If the deck slopes at 3/8 inch per foot, as it often does, the saddle needs to be at 3/4 inch per foot. And, architects and designers, the slope of the saddle is to the valley line, not the drain. The width of the saddle is the key and determining the width of the saddle is my secret.

It’s a simple formula:

(Distance Between Drain)x 33% = X

2

Increase X to the next number divisible by 4

Example: If the drains are 60 feet apart, divide 60 by 2 to get 30 feet; multiply 30 feet by 33% = 9.9 feet. Increase 9.9 to the next number divisible by 4 to get the answer: 12 feet.

Thus, the saddles at the mid-point apex should extend out three full tapered insulation boards. It’s best if you dimension this width on the detail.

On large buildings, the saddle width and thickness can be quite high, so be sure to double-check the insulation height with the height of the roof edge. I could tell you about a roof where the insulation rose several inches above the perimeter height because someone didn’t draw the detail to scale, but that is a story for another time.

Roof Drains in Four-Way Slope Roof Decks

Structurally sloped roof decks can be beneficial in that they can create positive drainage flow. But with four-way structurally sloped roof decks, the drain is not necessarily at the low point of the roof. How far off the low point is dependent on the plumbing contractor. I have seen drains installed several feet upslope. The plumbing drawings should have a note to the fact that the roof drain sump pan should be installed as close to the low point as possible.

Even when the drain is installed very close to the low point, it is still high and will result in water ponding in front of the drain. Thus, the low point needs to be artificially moved to the drain.

This is accomplished with a drain sump. Best practices suggest that the roof insulation be installed in two layers. This will allow for the installation of the sump.

Using Chicago as an example, which calls for R-30 or 5.2-inches of insulation, the first layer of insulation 2.6 inches thick is installed across the roof deck, to the roof drain. It should be cut to the roof drain extension ring. Fill the void between the roof drain and the insulation with spray foam; trim to the insulation. Next the tapered insulation sump is installed. To match the next layer of insulation, we use 1/2-inch-per-foot tapered insulation. It starts at 1/2 inch and, with a 4-foot panel, rises to a thickness of 2.5 inches. Placed around the drain, the sump created is 8 feet by 8 feet. The next layer of insulation is 2.5 inches and abuts the backside of the tapered insulation.

The 1/2-inch-per-foot slope is used as it doubles the slope of the structurally sloped roof deck, which in this case has a slope of 1/4 inch per foot.

Level Roof Decks With Tapered Insulation

Whether re-roofing or new construction, getting the drainage correct on level roof decks is still a challenge for most designers. Perhaps they don’t realize decks are not level; they have camber, they deflect, they undulate, and the drains are often near columns so the drain pipe can run along it. When the drain is near a column where no deflection takes place, it can often be high.

I like to first ensure the proper drain assembly has been selected and designed by the plumbing engineer: the roof drain, reversible collar, threaded extension ring, clamping ring, cast iron dome. (For more detail, see “Roof Drain Installation Tips” on page XX of this issue.) The sump pan should be selected and designed by the plumbing engineer and provided by the roof drain manufacturer — not by the metal deck supplier. (That the industry cannot get this correct is one on my pet peeves.) Do not raise drains off the deck with threaded rods. (See my article “Concise Details and Coordination Between Trades Will Lead to a Quality Long-Term Solution for Roof Drains,” RoofingMay/June 2016). If designing in a vapor retarder, it needs to extend to the roof drain flange and be clamped by the reversible collar. The first layer of insulation should be cut to fit and extend under and to the extension ring. Any voids should be sealed with spray foam.

To compensate for all the potential deck irregularities, I like to accentuate the slope into the roof drain by increasing the taper. More often than not, this means designing a 1/2-inch-per-foot slope sump into the drain. With a 4-foot board, this results in an 8-foot-by-8-foot sump. (See Figure 4 and Photo 3.) After detailing this sump, the main roof four-way tapered insulation can be designed and the heights at the perimeter calculated and noted on the plans. Just a reminder that the code-required thermal value needs to be attained four feet from the drain. So, for Chicago we detail to achieve R-30 at the backside of the tapered sump.

Final Thoughts

A new roof installation that results in ponding water at the drainage point is an unfortunate occurrence. Owners can be upset: “What is that?” “I didn’t pay to have water retained at the drains!” “Who is coming up and cleaning all this stuff off my roof?” Ponding water can be a standard of care issue for designers and result in damages. Learning to properly design rooftop drainage is not difficult, but it requires some thinking and some rooftop experience. Getting up on the roof during installations will help you visualize the needs to achieve proper drainage.

Making sure the roof system drains properly requires discussions with the structural engineers for new construction. I also find it helpful to have the plumbing contractor at pre-con meetings to review the interrelationship of the roofing and drains.

Getting water off the roof as quickly as possible has been a key priority for centuries — no matter the roof cover material. If the builders using stone can achieve complete and full drainage, then I challenge you to achieve it with the materials we use today.

Accella Performance Materials Announces New Vice President

Accella Performance Materials, a Carlisle Company, has promoted Joe Negrey to Vice President and General Manager of its Spray Polyurethane Foam (SPF) Insulation business unit. Negrey will oversee all business operations—helping to advance Accella’s commitment to bringing energy-saving, cost-efficient SPF technology to the North American and global markets.

A veteran within the polymers space, Negrey has more than two decades of process engineering, product development, sales, marketing and manufacturing experience in the polyurethane systems industry. Prior to assuming this current role, Negrey served as Vice President of Accella’s Tire Fill division where, under his leadership, the brand’s foam fill product business for the Off-the-Road tire industry grew to become the recognized international category leader.

Negrey has also served in various other capacities within the Accella brand family, and held positions as Operations Manager, Director of Operations, and Vice President of Operations. His strengths lie in his visionary leadership and strategic planning capability—and excellent team management approach. Negrey holds a bachelor’s degree in Industrial Technology from California Polytechnic State University.

For more information, visit www.accellacorp.com.

Contractor Conquers Tough Weather, Tight Schedule

The roof on the new Goodman Logistics Center (the building on the right) encompasses more than 1 million square feet. The roof system installation met an aggressive timeline that spanned the winter months. Photo: Goodman Carlisle LLC

Goodman, an international commercial and industrial property group, approached Donald B. Smith Inc. of DBS Roofing in November 2017 to support the roofing of the company’s new Logistics Center in central Pennsylvania.

Founded in 1948, DBS Roofing is a second-generation, privately held company whose principles of quality and workmanship have earned the team countless awards. Among those honors include the Firestone Master Contractor recognition, the Baltimore Builder’s Exchange “Craftsman of the Year Award” and numerous industry publication recognitions for notable projects.

The Logistics Center roof was 1,010,000 square feet and was established on a very aggressive timeline that spanned through the tough Northeast winter months. The initial specifications of the job called for a mechanically fastened TPO roof system, which was going to be challenging with the size and timeline of the project. Additionally, the condensation levels in central Pennsylvania are not ideal for mechanically fastened solutions, as it would require applying a vapor barrier and foam around all perimeters, exceeding the original budget and schedule.

To save time and keep the project moving forward during the unfavorable winter conditions, DBS Roofing elected to use one of the company’s favorite “box world” solutions — Firestone Building Products (FSBP) UltraPly TPO SA with Secure Bond Technology.

Photo: Goodman Carlisle LLC

The TPO roofing system is comprised of a self-adhering membrane with factory applied, pressure sensitive adhesive and technology designed to ensure uniform adhesion coverage across the entire membrane. According to the manufacturer, the system can be installed in weather as cold as 20 degrees Fahrenheit.

“Commercial roofing in central Pennsylvania can be very challenging during the winter season, but Firestone UltraPly TPO SA allows our business to continue working through those conditions and prosper,” says Donnie Sanders, president of construction, DBS Roofing. “Being able to apply the Firestone TPO SA at 20 degrees resulted in a successful year for us.”

The Goodman Logistics Center roofing project began on November 1, 2017 and was completed on time March 1, 2018.

TEAM

Roofing Contractor: Donald B. Smith Roofing Inc., Hanover, Pennsylvania, www.dbsroofing.com
General Contractor: ARCO Design/Build Northeast, King Of Prussia, Pennsylvania, http://arcodbi.com

MATERIALS

Membrane: UltraPly TPO SA with Secure Bond Technology, Firestone Building Products, www.firestonebpco.com
Insulation: 2.5-inch ISO, Firestone Building Products

New Facility Keeps Popular Brewery Hopping

Tree House Brewing opened its new 51,200-square-foot brewery in Charlton, Massachusetts in July of 2017. Photos: Sika Sarnafil

Standing in line for hours for one case of canned beer might seem foolish to some people, but to fans of Tree House Brewing — which was recently named one of the country’s Top 15 Craft Breweries by Forbes magazine — it is well worth it. Tree House Brewing began humbly enough in 2011 in a barn in Brimfield, Massachusetts. And yes, there was a tree house on the property.

Since then, the brewery has grown so much in popularity that it required a bigger facility.  So in July of 2017, Tree House opened a 51,200-square-foot brewery on 68 acres in Charlton, Massachusetts. On opening day, the new facility consistently had 1,000 customers waiting for hours to purchase Tree House’s ales, IPAs and stouts. Many of the patrons traveled from out of state and some arrived at 6 a.m., six hours before the doors opened.

It’s been said that the key to Tree House Brewing’s success is meticulous attention to details such as temperatures, additives and the water used in the brewing. It only made sense that the same attention to detail would be utilized when selecting a roofing system for the new facility.

Meeting the Bar

The roof that Tree House Brewing selected to cover its new brewery is Sika Roofing’s Sarnafil EnergySmart PVC membrane installed with the Sarnafil RhinoBond System. “We like Sarnafil because it is easy to use, easy to specify and an industry leader,” says Peter Webster, designer/project manager at Austin Design in Brattleboro, Vermont. “The light colored, reflective roof also offers energy savings, and our past experience with the Sarnafil roof shows it is a great product.”

The roof system for the new brewery features Sika Roofing’s Sarnafil EnergySmart PVC membrane, which was installed using the Sarnafil RhinoBond System. Photos: Sika Sarnafil

The fact that the Sarnafil system is easy to install was an important factor, considering the time crunch of the project. “This was a ‘hurry up’ project — we weren’t done with the design when the steel structure went up,” Webster explains.

The Sarnafil RhinoBond System uses advanced induction welding technology to bond the membrane directly to specially coated plates used to secure the insulation to the deck, all without penetrating the roofing membrane.

In addition, the Sarnafil RhinoBond System can be used in temperatures as low as zero degrees Fahrenheit (-18°C), making it an ideal application method for winter projects.

“Much of the installation was during the winter,” states Robert Luukko, president of Kidd-Luukko Corporation in Worcester, Massachusetts, the roofing contractor on the project.

Photos: Sika Sarnafil

“Not only did Kidd-Luukko have to deal with cold temperatures, but the site is on top of a hill so there were high winds,” says Frank Quigley, president and owner of F.D. Quigley & Associates of Wilbraham, Massachusetts, the construction manager on the job. And of course, since it was winter they needed to make the building watertight as quickly as possible.

“Fortunately, Kidd-Luukko was able to seal the building before we were hit by some big snowstorms in February,” Webster says.

Other challenges included installing a 42-foot by 8-foot skylight and working around gables where the low roof wrapped around the corners. “Kidd-Luukko employees were very professional, well managed and well organized,” Quigley states. “I’d be happy to use them again.”

“Can-Do” Attitude

“Bob Luukko and his team had a ‘can-do’ attitude that really helped move the project along,” Webster comments. In fact, Kidd-Luukko was able to complete the installation ahead of the allotted eight-month time frame, Luukko notes, adding that teamwork was key. “We had weekly meetings with a great group of guys involved with the project where we would discuss how we were going to come in on time and on budget with this installation,” he says. Sika Roofing representatives also played a role in meeting the deadline. “We had multiple visits from the Sika technician, which really kept the project moving forward,” Luukko remarks.

After a vapor barrier was applied on the metal deck, crews installed polyiso insulation, tapered insulation and a high-density cover board before the membrane was attached. Photos: Sika Sarnafil

Today, both the roof and the brewery are doing great. “We’ve had no problems with the roof at all,” Webster says. Luukko adds, “This project went so well that we are receiving a lot of interest in installing Sarnafil roofs on other projects.”

At the new facility, Tree House Brewing will be able to produce 40,000 barrels a year — compared to 12,000 barrels at their former facility in Monson, Massachusetts — and they plan to eventually expand the capacity to 180,000 barrels a year. That’s news that should make thirsty Tree House beer fans very, very happy.

TEAM

Architect: Austin Design, Brattleboro, Vermont, www.austindesign.biz
Construction Manager: F.D. Quigley & Associates, Wilbraham, Massachusetts, www.fdquig.com
Roofing Contractor: Kidd-Luukko Corporation, Worcester, Massachusetts, www.kidd-luukko.com

MATERIALS

Roof Membrane: Sarnafil 60 Mil EnergySmart White PVC membrane, Sika Sarnafil, https://usa.sarnafil.sika.com
Insulation: Sarnatherm Poly-Iso Insulation and Sarnatherm Coated Glass Tapered Insulation, Sika Sarnafil
Roof Board: Sarnatherm High Density Poly-Iso roof board with coated glass facers, Sika Sarnafil
Attachment System: Sarnafil RhinoBond System, Sika Sarnafil