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Metal Ventilation Guide

Where determined necessary by the building official due to atmospheric or climatic conditions, enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters shall have cross ventilation for each separate space by ventilating openings protected against the entrance of rain and snow. The net free ventilating area shall not be less than 1/150 of the area of space ventilated.

Soffit Vent Net Free Ventilating Area
Hole Size
Point-to-Point
Ground
3/8"
1/2"
3/4"
7/8"
1 3/8"
1/8"
0.75
0.59
0.59
1/8"
1.00
1.77
1.77
1.18
1/8"
1.50
2.36
2.36
2.36
2.36
1/8"
2.00
4.12
4.12
3.53
3.53
3.53
1/8"
2.50
5.30
5.30
4.12
4.12
4.12
1/8"
3.00
5.89
5.89
5.89
5.89
5.89
1/8"
3.50
7.07
7.07
7.07
6.48
6.48
1/8"
4.00
8.25
8.25
8.25
7.66
7.66
1/4" (J Series)
2.00
6.28
6.28
6.28
6.28
6.28
1/4" (J Series)
2.50
7.85
7.85
7.85
7.85
7.85
1/4" (J Series)
3.00
11.00
11.00
11.00
11.00
11.00
1/4" (J Series)
3.50
12.57
12.57
12.57
12.57
12.57
1/4" (J Series)
4.00
14.14
14.14
14.14
14.14
14.14
Note: NFVA is stated in square inches per foot of vent length.

Hole Reference
Vent Holes:
Are for air flow. Available in 1/8” (V) or 1/4” (J)
Weep Holes:
Are for water/moisture release. Available in 1/8” (W), 1/4” (J) or 1/2” (L)
Key Holes:
Are to give mud/stucco something to grab on to providing a mechanical bond. Available in 1/8” (K).
Nail Holes:
Are to allow easy installation by providing pre-spaced holes in the flange to secure the product. Available in 1/8” (N).
Note: Some products may offer both Vent and Weep deferent locations of the same product.