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Unvented Attic Insulation Application

Unvented Attic Insulation Application

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Spray foam in unvented attics

Spray foam in unvented attics allows homeowners to convert the area into a liveable space. Common problems found with traditional insulation in an unvented attic assembly can be mitigated with spray foam insulation like Icynene. Spray foam in unvented attics intended for regular use helps:

  • keep bulk moisture out (closed-cell spray foam is a water-resistive barrier)
  • allow the roof sheathing to dry towards the inside (with open-cell spray foam)
  • protect against condensation and mold growth
  • maintain even temperatures throughout the attic space

In a living space, mechanical ventilation is recommended to maintain the required number of air changes and good indoor air quality. Adding an energy recovery ventilator (ERV) or ventilation with heat exchange and a humidistat/timer can help achieve this.

Unvented attics in hot, humid climates

In a hot, humid climate, an unvented attic assembly with HVAC equipment can be subject to extreme heat conditions. Spray foam in unvented attics helps convert the space for more optimal performance of the HVAC unit. Sealing soffit vents with Icynene can control wind-driven moisture ingress for added durability, and prevent burning embers from entering the attic. Furthermore, insulating the unvented attic assembly with Icynene foam insulation helps:

  • keep any duct leakage within the conditioned space for better efficiency
  • allow for easy detection of roof leak sources for easy repair and return to optimal performance once dried (open-cell spray foam)
  • keep the attic temperature within 5°F - 10°F of the living environment below

Unvented attic code references

Unvented attic assemblies

  • Local codes based on IRC 2009: Section R806.4
  • Local codes based on IRC 2012 and 2015: Section R806.5

Foam plastic (spray foam)

  • Local codes based on IRC 2009, 2012 and 2015: Section R316

Energy efficiency of building thermal envelope

  • Local codes based on IRC 2009, 2012 and 2015: Section N1102