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Spray Foam Insulation Application On Underside of Roof Decks

Commercial building roofs, typically metal, have large surface areas, which can lead to substantial heat loss and/or gain. Critical design considerations of flat or low-pitch commercial building roofs include:

  • simplicity of the installation
  • thermal performance
  • initial cost, maintenance costs and lifetime costs
  • life expectancy
  • detection of roof leaks

In the 2015 IBC, Section 1203.3, the requirements for unvented attic and unvented enclosed rafter assemblies are noted. As air-impermeable insulation, spray foam insulation can be used in such applications.

Spray foam insulation applied on the underside of the roof deck in cold-climate commercial buildings allows for a significant reduction in condensation potential, particularly compared to interior air-permeable batt systems. In warmer climates, the creation of an unvented attic results in a more hospitable environment for the efficient operation of HVAC equipment.

Warm indoor air can hold a large amount of moisture and can generate serious problems if allowed to make contact with cold roof surfaces. Icynene spray foam insulation inhibits the movement of humid indoor air up to the underside of the roof deck, helping to prevent condensation forming. It’s worthwhile to consider that a vapor retarder may be required where high interior humidity or extreme climate conditions exist or where building codes require it.

Additionally, spray foam on the underside of the roof deck:

  • can reduce construction schedules due to reduced access needs
  • maintains form over the long term
  • adheres to commonly used substrates
  • easily insulates penetrations and unusual roof shapes, including domes and arches