4.1088.1 Attic Ventilation

Topic: 
Attics
Subtopic: 
Special Considerations
Desired Outcome: 
Properly restored vents minimize moisture and ice dams
For supporting material, see Calculation of the Infiltration Credit, Referenced Standards and Building America Solution Center.
TitleSpecification(s)Objective(s)
4.1088.1a
Air barrier Air barrier The separation between the interior and exterior environments of a building that slows air flow to the point that no smoke movement is visible at 50 pascals of pressure difference across the boundary and thermal boundary Thermal boundary The separation between the interior and exterior environments of a building that slows heat flow

Attic ventilation will be recommended or installed if local code requires attic ventilation during weatherization or retrofits

The presence of an effective air barrier Air barrier The separation between the interior and exterior environments of a building that slows air flow to the point that no smoke movement is visible at 50 pascals of pressure difference across the boundary and thermal boundary Thermal boundary The separation between the interior and exterior environments of a building that slows heat flow between the attic and the living space must be verified and appropriate attic sealing and proper insulation is specified as part of the scope of work

Ensure presence of continuous air barrier Air barrier The separation between the interior and exterior environments of a building that slows air flow to the point that no smoke movement is visible at 50 pascals of pressure difference across the boundary and thermal boundary Thermal boundary The separation between the interior and exterior environments of a building that slows heat flow

4.1088.1b
Vent type

Attic vent types will be made of corrosion-resistant material for their specific location (e.g., exterior soffit, gable end, roof ) and material and intended use (e.g., metal vent on metal roof )

Attic-powered ventilators will not be used

Ensure vent meets proper performance characteristics for location and roofing type
4.1088.1c
Vent location

Placement of attic vents will be considered for proper air flow and prevention of entry of wind driven rain or snow

Encourage proper air flow

Minimize entry of wind driven rain or snow
4.1088.1d
Ventilation baffling

Baffling for attic soffit vents will be installed to:

  • Ensure proper air flow
  • Prevent wind washing of insulation
  • Allow maximum insulation coverage
  • Ensure baffle terminates above insulation

Ensure vent allows proper air flow without compromising insulation performance
4.1088.1e
Ventilation screens

All attic ventilation will have screens with non-corroding wire mesh with openings of 1/16" to 1/4" to prevent pest entry (e.g., birds, bats, bees)

Existing vents that are not screened will be covered with non-corroding wire mesh with openings of 1/16" to 1/4"

Ensure net free area requirements are met

Additional vents or larger vents can be added if screen size is smaller than designated

Prevent pest entry