crawl space ventilation
 

crawl space ventilation
does anyone know the proper area to use for an 8"x16" crawl space ventilation opening. obviously the net area is not simply 8 times 16, and it probably differs from manufacturer to manufacturer but does anyone know a conservative number to use.
the net free area is calculated by multiplying the total area of the vent by 0.44 for consideration of reduction in air flow due to the presence of louvers and screens.
that's probably a good number to use for approximations but various screens, meshes and louvers all have different values. i just did a flood vent for some crawlspaces in a flood zone and the particular screen i used had a net opening of 72% of gross area.