Vent and Insulation Clearance in the 2009 IRC


For rafter framed or truss framed roof construction, not only is ventilation of these cavities required by the 2009 International Residential Code, but a minimum air flow clearance is required to maintain the path of ventilation. Per the 2009 IRC, Chapter 8, Section 806.3, here is the excerpt for this requirement:

R806.3 Vent and insulation clearance. Where eave or cornice vents are installed, insulation shall not block the free flow of air. A minimum of 1-inch (25 mm) space shall be provided between the insulation and the roof sheathing and at the location of the vent. 

Here are a couple more articles related to required attic ventilation, Don’t Make Your Solid Blocking Too Solid – Attic Ventilation Requirements and Typical Rafter Insulation Detail.


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