Am reroofing now & adding ridge vent, so need to know my eave air flow.
Have exposed 4x6 cedar rafters with 1x6 between them - no soffit. Each 1x6
has 3 (2" diam) holes backed with wire screen. In theory, I would think I
have 3 x 6.28 sq in air flow reduced by the wire screen (50%?) per 1x6
board. The 'coons & squirrels have gotten through the screen multiple times
over the years, so I've stapled a standard metal 4x16 undereave vent (air
flow rated at 28 sq in each) to the backside of each 1x6. Now what do I
have?

Attic Ventilation rule...

Area of ceiling adjacent to the attic divided by 300 for a home less than 20
years old.
(divide by 150 for older homes)

Take resulting square ft and divide by 2

This will give you the required square feet of upper and matched reqired
ventilation are for lower ventilation.

Example: 2000 sq ft of ceiling / 300 = 6.7

6.7 / 2 = 3.3

The example home needs 3.3 square ft (480 sq inches) of upper ventilation
and the same for lower ventilation.

TAB Dude

TAB Dude wrote:
Attic Ventilation rule...

Area of ceiling adjacent to the attic divided by 300 for a home less than 20
years old.
(divide by 150 for older homes)

Explain this please. It's such a blanket (batt?) statement that I
don't understand what you mean.

R

Attic Ventilation rule...

Area of ceiling adjacent to the attic divided by 300 for a home less than
20 years old. (divide by 150 for older homes)

Thanks for looking, TAB Dude, but that's not the question. I think I know
what my
target *should* be. What I need to know is what rate I'm *now* getting for
the eave part after combining the 2" holes & the metal eave vent.