Spray Polyurethane Foam (SPF) Insulation on Metal Roof and Wall Panels

With building code compliance and sustainable building envelopes at the forefront in today’s marketplace, spray polyurethane foam insulation (SPF) applied to single skin metal roof and wall panels is an alternative to insulated metal panels with a manufacture-applied polyurethane foam core. SPF insulation improves a building’s energy efficiency and provides thermal, air and vapor barrier capabilities.

What Is Spray Polyurethane Foam (SPF) Insulation?

SPF insulation consists of isocyanate and polyol resin that is chemically combined and applied to surfaces using a spray gun. SPF insulation can be open cell or closed cell.  Open-cell foam provides insulation and air sealing for a building, but is water and vapor permeable. Closed-cell foam provides better insulation than open cell and also functions as an air barrier. Closed-cell foam differs from open cell in that it prevents water entry, minimizes moisture vapor permeability and decreases air leakage, making it the preferred insulation to apply to metal panels.

Spray Foam Insulation with Metal Panels
Spray Polyurethane Foam Insulation with Metal Panels. Image courtesy of Spray Polyurethane Foam Alliance

SPF insulation is well suited for use as interior insulation for metal wall and through-fastened metal roof panels. The traditional thermal insulation layer—one or two layers of batt insulation with a facer—has its intricacies; for example, compressed areas and difficulty taping seams at edges and penetrations for air barrier performance.  But because of SPF’s inherent physical characteristics and spray application method, SPF overcomes many obstacles.

8 Application and Safety Tips for SPF

Using SPF to fully insulate and seal a building with metal panels can have unintended consequences if the material characteristics and project parameters are not well thought out. The Metal Construction Association (MCA) recently conducted research with the Spray Polyurethane Foam Alliance (SPFA) and published their findings in a technical bulletin. It includes the following best practices and considerations for installing SPF.

Image courtesy of Spray Polyurethane Foam Alliance
  1. Utilize a certified foam spray technician to ensure the insulation meets the desired thickness, density and adhesion.
  2. Only apply SPF to clean, dry areas.
  3. SPF should not be used on standing seam metal roof panels because it may restrict the thermal movement of the panels, causing distortion.
  4. Follow a “picture frame” application technique, further detailed here, to prevent SPF from getting between girts and metal panels, causing deformation.
  5. Notify other contractors, including HVAC and electrical, to ensure necessary precautions are made.
  6. Follow building code requirements for fire protection because in some instances SPF may meet thermal barrier requirements.
  7. Prevent SPF chemicals from being drawn into a building’s ventilation system during and after installation. There may be a mandated wait time before other occupants can reenter the space.
  8. Consult with your metal panel manufacturer before applying SPF.

Read more recommendations and findings by the MCA by downloading their technical bulletin, Spray Polyurethane Foam Insulation on Interior Surfaces of Metal Panels, here.

All Those Sustainability Acronyms Mean Something, Right?

PCR, LCA, EPDBy now I’m sure you’ve heard about PCRs, LCAs, and EPDs.  Simply put, a PCR is a set of product category rules; an LCA is a life cycle analysis; and an EPD is an environmental product disclosure.  But what do they mean and what’s the purpose of it all?  In the broadest sense, these are mechanisms used for the sustainability movement.  The most granular is the EPD, which is a product-based discussion (i.e., disclosure) of the environmental effects caused by a specific product or product type.   Architects and building designers use EPDs to compare products in order to select the most environmentally friendly products to be used in environmentally friendly buildings.

Developing an EPD can only happen after the creation of a set of product category rules (PCR).  A PCR sets the rules for creating LCAs and EPDs.  An example of a PCR is “Product Category Rules for Preparing an Environmental Product Declaration (EPD) for Product Group: Insulated Metal Panels & Metal Composite Panels, and Metal Cladding: Roof and Wall Panels,” which was developed by UL through the efforts of the Metal Construction Association (MCA).

Only after a PCR is developed can a verifiable LCA or EPD be developed.  An LCmA and EPD are similar but different.  An LCA uses industry-average data, and an EPD is specific to a product or product type.  For example, “LCA of Metal Construction Association Production Processes, Metal Roof and Wall Panel Products” provides industry-average information about the environmental aspects of three key products: steel insulated metal panels, aluminum metal composite material panels, and steel roll-formed claddings.  This LCA is based on 24-gauge material.

EPDs are typically more product specific.  (An EPD is typically based on an LCA, so most often LCAs are developed prior to EPDs.)  For example, the EPD titled “Roll Formed Steel Panels For Roof and Walls” provides similar environmental data as an LCA, but includes information about 29-, 26-, 24-, 22-, 20- and 18-gauge materials.  This provides additional product specific information that can be used by designers when an industry average is not adequate.  And importantly, more LEED points are garnered from a product-specific EPD than an LCA because of the specificity.  LEED is certainly a driver of this!

LCAs and EPDs used in the roof industry are often focused on cradle-to-gate analysis, and exclude the use phase and end-of-life phase.  Ideally, an LCA or EPD should include the use and end-of-life phases so architects and designers have a complete cradle-to-grave analysis.  Without the use phase, designers are allowed to freely select the service life of a metal roofing product, for better or worse, without industry guidance.  And, the advantages gained through metal recycling at the end of life are also omitted from MCA’s LCA.

It’s all about standardized disclosure of environmentally based product data.

Learn more about MBCI’s LCA, EPDs and other sustainability efforts, here.

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