Polyiso Insulation Products Allow Applicators to Manage Adhesive Flash-Off Times

Carlisle SynTec Systems introduces ReadyFlash Technology for SecurShield flat and SecurShield HD polyiso insulation products. ReadyFlash Technology allows applicators to manage adhesive flash-off times by choosing between two different-colored facers on every board. ReadyFlash products feature a dark-colored coated-glass facer (CGF) on one side of the insulation board and a light-colored CGF on the other.

Utilizing the sun’s energy, the dark facer accelerates adhesive flash-off, while the light facer slows it down. Applicators can choose which side of the board to use, helping to offset environmental variables affecting adhesive flash-off such as temperature, sunlight, humidity, wind speed, size of crew, current pace, and time of day. 

ReadyFlash Technology benefits include: 

  • Allows the applicator to speed up or slow down adhesive flash-off time. 
  • Increases surface temperature of the dark facer up to 50°F(28°C) above ambient temperature. 
  • Decreases surface temperature of the light facer up to 10°F (6°C) below ambient temperature. 
  • Provides up to 2x faster adhesive flash-off on cooler days and up to 4x faster on warmer days when utilizing the dark face. 

For more information, www.carlislesyntec.com.

Coated Glass Facers Bring New Performance Advantages to Polyiso Insulation

Photos: Owens Corning

Rigid polyisocyanurate (polyiso) insulation board is one of the most widely-used insulation products on the market today and is manufactured in various forms for use in wall, roof, and other building construction applications. The different types, classes, and grades of polyiso insulation board are defined by the classification system in ASTM C1289 “Standard Specification for Faced Rigid Cellular Polyisocyanurate Thermal Insulation Board” and may be classified by the type of facer or facing material used to manufacture the products.

Polyiso is a thermoset, closed-cell, rigid foam plastic insulation that is manufactured in board form (typically 4-foot-by-4-foot or 4-foot-by-8-foot sizes). Through a continuous lamination process, liquid raw materials that make up the foam formulation are mixed and in a rapid chemical reaction form a rigid and thermally stable polymeric structure. During manufacture, the facers or facing materials enable the manufacturing process by containing the viscous foam mixture as it is poured and cured into the rigid polyiso core.

After manufacture, facers or facing materials perform a number of key functions for the installation and use of polyiso products. At the jobsite, the specific type of facer or facing material can determine the insulation product’s compatibility with various substrates, which is an important consideration where installed as part of an adhered roof system. Once installed in a roof system, the facer or facing material can influence water absorption and water vapor transmission, which can be important characteristics in building envelope applications. In wall applications, polyiso may be used as a drainage plane to shed bulk water and with taped joints between adjacent boards can form both effective water resistive barrier and air barrier component. Facer or facing materials can positively contribute to the fire performance of the product and assembly, reduce air movement through the system, or provide for radiative properties. Finally, it should be noted that the same facer material is typically used on both sides of the polyiso board; however, different facer types may be used to meet specific project design and performance needs.

Facer Types

The three most common types of polyiso facers are aluminum foil, glass fiber reinforced cellulosic felt, and coated polymer-bonded glass fiber mat. The ASTM C1289 Standard contains classifications and descriptions for each facer type:

  • Aluminum Foil Facer (FF) is composed of aluminum foil that may be plain, coated and/or laminated to a supporting substrate.
  • Glass Fiber Reinforced Cellulosic Felt Facer (GRF) is composed of a cellulosic fiber felt containing glass fibers.
  • Coated Polymer-Bonded Glass Fiber Mat Facer (CGF) is composed of a fibrous glass mat bonded with organic polymer binders and coated with organic polymer, clay, or other inorganic substances.

Polyiso products as shown in Table 1 may also be manufactured with other facer types or facing materials such as uncoated polymer-bonded glass fiber mat (AGF), perlite insulation board, cellulosic fiber insulation, oriented strand board (OSB), plywood, and glass mat faced gypsum board. Depending on the particular project requirements, a certain facer type may offer specific benefits and the most attractive option for that application.

Coated Polymer-Bonded Glass Fiber Mat Facer

Coated polymer-bonded glass fiber mat facer (coated glass facer or CGF) is used in polyiso insulation products installed as part the building enclosure, including roof insulation, high-density cover board, and wall insulation products. Coated glass facers consist of multi-layer construction and a coating to impart a versatile weather resistant outer layer. CGF facers offer dimensional stability and resistance to water absorption. The glass fibers in the mat provide tensile strength and moisture resistance characteristics, making the mats an ideal solution for other product applications that require high levels of performance link flooring products, underlayments, asphalt shingles, roof membranes, ceiling tile, and other construction products (i.e., glass reinforced panels and industrial applications).

The CGF Manufacturing Process

For polyiso products, the CGF consists of a non-woven glass fiber mat as the substrate. The glass fibers that make up the mat are formed when minerals are batched together, melted in a large furnace, and extruded into strands through fine orifices in bushing plates. The fibers are mechanically drawn, cooled, and treated to impart the required handling and physical properties for the desired performance.

For non-woven applications, the fibers are chopped to the required length and sent to the mat forming line. The non-woven glass fiber mats (typically produced by a wet laid process on an inclined wire former) are impregnated with a synthetic water-based binder such as acrylic, urea formaldehyde, or renewable organic binders. The impregnated web is dried and cured in a direct gas-heated belt dryer. To produce the final coated glass facer, the rolled mat is coated with a mineral-filled latex coating to seal the mat. The coated mat is rewound and packaged according to individual product and customer specifications. After inspection, the mats are slit and wound in-line on cardboard cores in a turret winder.

The rolls of CGF are delivered to polyiso manufacturers where they are loaded into laminators to become the top and/or bottom facers of the finished polyiso insulation boards.

CGF and Polyiso Performance Benefits

Coated glass facers do more than hold the polyiso together as it cures; they add certain performance characteristics that can enhance the effectiveness of the final polyiso product. CGF as a material is noted for offering the following benefits for polyiso insulation:

  • Mold resistance
  • Enhanced fire performance
  • Excellent strength and durability
  • High moisture resistance
  • Excellent dimensional stability
  • Resistance to delamination
  • A reduction in knit line appearance

Since every type of polyiso product has its unique advantages and uses, choosing the right facer for the right application can have long-term impacts on the entire system’s performance and resilience. For example, some moisture is always present in our environment. CGF can provide added resistance to moisture absorption for polyiso products and help improve the performance and durability of the overall roof system.

Polyiso insulation products offer:

  • A high R-value per inch compared to other insulation products.
  • A certified LTTR value (roofing products).
  • The performance to meet today’s code required R-values while minimizing assembly thickness, and material and labor requirements.
  • Excellent performance in fire tests.
  • Ease of use and peace of mind, as polyiso products are designed for use in an expansive assortment of tested, approved, and code-compliant assemblies.
  • As a thermoset plastic, stability over a large temperature range (-100°F to +250°F) and can be used as a component in roof systems utilizing hot asphalt.
  • Versatility as a multi-attribute weather barrier product.
  • A continuous insulation solution to minimize heat loss through thermal bridges.

In summary, the combination of polyiso insulation and coated glass facers provide building owners and contractors with a solution that can meet thermal, moisture, and durability considerations. A wide variety of CGF polyiso products are available for specific applications in roofing or wall construction. Consult with a polyiso manufacturer for guidance on design and technical information for various insulation systems. Further information can be found at www.polyiso.org, the website of the Polyisocyanurate Insulation Manufacturers Association (PIMA), along with updated Environmental Product Declarations (EPDs), and technical bulletins for polyiso applications.

About the author: Marcin Pazera, Ph.D., is the Technical Director for Polyisocyanurate Insulation Manufacturers Association (PIMA). Dr. Pazera coordinates all technical-related activities at PIMA and serves as the primary technical liaison to organizations involved in the development of building standards. He holds a doctoral degree in mechanical engineering from Syracuse University and, over the course of his career, has worked in building science with a focus on evaluating energy and moisture performance of building materials and building enclosure systems. He has expertise in building enclosure and product manufacturing encompassed-research, testing, product conception and development, and computer modeling/analysis.

Polyisocyanurate Foam Insulation Board

IKO offers Ener-Air, an energy efficient, vapor-permeable, noise-reducing wall insulation board with outstanding R-value. Ener-Air is constructed from closed cell polyisocyanurate foam core bonded on each side to coated fiberglass facers during the manufacturing process. The product is lightweight and easy to cut, thus reducing labor costs on site. Plus, stud and fastener line indicators improve accuracy of installation. Ener-Air serves as a superior building envelope insulation product to meet a wide variety of commercial building needs. IKO Ener-Air has a high thermal R-value of R6 per inch (RSI 1.05 per 25 mm), providing superior insulation protection, which helps to reduce energy costs and increase efficiency.

For more information, visit www.iko.com.

Metal Building Insulation Offers 10-Year Warranty

New rFOIL Ultra White 2600 Series metal building insulation offers a 10-year UV degradation warranty on material flaking and labor cost. According to the manufacturer, Ultra White blocks 97 percent of radiant heat transfer and prevents interior condensation. Ultra White is a single or double layer of polyethylene bubbles bonded to and sandwiched between a radiant barrier metalized foil and white polyethylene sheet. Designed to control heat gain and loss in all types of metal and metal-clad buildings, Ultra White features Quickseam-Taped Tabs for easy handling and installation. Puncture- and tear-resistant Ultra White is not affected by humidity and will not support mold and mildew.

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

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.