Roofs are the often-overlooked superstars of buildings. They are the first line of defense against all types of weather, including heat and cold. As part of a building system, the roof and its insulation are just as important as walls, windows and mechanicals in maintaining comfortable temperatures within a building.
retrofit recently had the opportunity to discuss the benefits of polyiso insulation for roof retrofits with Justin Koscher, president of the Polyisocyanurate Insulation Manufacturers Association (PIMA). The association represents manufacturers of polyiso, raw materials suppliers and businesses that provide testing services to manufacturers, all of whom seek to educate the design and construction industry about the benefits of polyiso.
Q: What makes polyiso insulation a popular choice for reroofing projects?
A: As a rigid foam board insulation, polyiso has one of the highest R-values per inch compared to other insulating options, providing excellent resistance to heat transfer. It is also lightweight and widely available in incremental thicknesses, typically ranging from 1 inch to 4 1/2 inches with greater thickness options available. Because of its proven performance and design versatility, building teams can utilize polyiso in a multi-layered system with staggered joints to successfully achieve the desired R-value in their reroofing projects and meet energy-efficiency goals.
Many architects, specifiers and contractors turn to high-density [HD] polyiso roof coverboards to add R-value while enhancing the overall durability of the new roof system. The high-performance solution can help extend the life of a roof assembly by providing a tough, resilient layer for improved wind-uplift resistance, increased impact resistance from construction/service traffic and high compressive strength. HD polyiso coverboards also are lightweight, which means they are easy to maneuver and install.
Q: One of the primary reasons for roof failures is moisture intrusion or ponding water. Can polyiso insulation products help provide a solution?
A: It makes sense that shedding water is generally deemed one of the primary functions of a well-designed roof assembly. But a roof’s ability to shed or drain water effectively has less to do with the roof membrane itself and more to do with the overall assembly’s ability to control the flow of water and direct it toward proper drainage devices. By employing a tapered roof insulation system, building teams can create slopes in any direction, which can help reduce or nearly eliminate the risk of ponding water. These systems can be particularly effective in retrofit projects that lack proper roof slopes and conditions where achieving the desired slope through structural changes is impractical or cost-prohibitive. The use of tapered polyiso insulation can be incorporated for optimal roof performance.
A code-compliant approach to water management, tapered polyiso insulation systems offer numerous benefits, in addition to providing positive drainage: enhanced thermal performance to meet energy-code requirements, versatility, customization to accommodate project-by-project complexity and compatibility with other roof system components.
Q: What are the energy-code requirements for reroofing projects? Are there benefits to code-compliant roof upgrades?
A: Current energy codes require that new roofing systems—whether installed on new or existing buildings—meet the minimum R-value requirements for the building thermal envelope. This means that if the local codes require roof systems of newly constructed buildings be a minimum of R-25, the systems installed as part of roof replacements also need to meet that criterion. Although the required R-value primarily depends on climate zones and local code adaptation, base values generally range from R-25 to R-35.
In the same vein, reroofing projects that use high-performance insulation can help design teams enhance the energy efficiency of a building envelope and, in turn, reduce its carbon footprint. The quantitative benefits of energy-efficient roof replacements are highlighted in a recent study commissioned by a coalition of insulation trade associations, including PIMA. For example, the study found that over a 30-year service life, simple building envelope insulation upgrades can offset emissions associated with 40 percent of total natural-gas-fired generation in the U.S. The study’s findings underscore the potential of utilizing proven polyiso solutions, like HD coverboards and tapered insulation systems, in reroofing projects to meet energy-code requirements.
Q: What about the environmental impacts of polyiso? Are there resources available that share more details?
A: Yes, PIMA maintains third-party verified, ISO-compliant Environmental Product Declarations, or EPDs, that provide industry-averaged environmental impact information for polyiso roof insulation, HD polyiso coverboards and polyiso wall insulation manufactured across the U.S. and Canada. These cradle-to-grave reports cover the full product life cycle of polyiso insulation over a 75-year building service life as specified in the Product Category Rule for thermal insulation. They include environmental impacts from the supply and transport of raw materials, as well as the manufacturing, transportation, installation, replacement (in the case of roofing materials) and disposal of polyiso products.
In particular, the EPD specific to roof insulation boards covers polyiso roof insulation manufactured with glass reinforced facers and polymer-bonded coated glass facers at specific product thicknesses. The report includes an analysis that explains how the environmental impacts from the manufacturing process are quickly recouped through building energy-use savings when polyiso is installed on existing buildings as part of a roof replacement project. It also illustrates how by utilizing environmentally conscious and high-performing polyiso insulation products, building teams can champion energy requirements and meet sustainability benchmarks.
PHOTOS: Polyisocyanurate Manufacturers Association