Doug wrote:

"George E. Cawthon" wrote in
:

...

You don't want too much ventilation so don't get over 6
square feet of free air space (or 18 square feet of actual
measured louvered and screened vents).


This is the first time I've ever read that one can have too much
ventilation. Are you sure about that? Every manufacturer's vent
instruction and other recommendations I've read always phrase ventilation
requirements as minimums. Never anything mentioned about problems with
exceeding those minimums. They do indicate a 50/50 balance between high
and low vents is best and, if there's an inbalance, the low vent free area
should be greater than the high vent free area.

Doug

Sure there is, especially in cold climates. If you have a
50 mile an hour wind outside and enough vents to have a 50
mile an hour wind through your attic, that wouldn't be
good. Now if you had 40 inches of insulation and it was
tied down tight, it might be ok.

What you really need (especially in a cold climate) is
enough venting to get rid of the moisture but not so much
that you have to have an unreasonable amount of insulation.
An attic getting warm from sunshine during a cold day is
much preferable to an attic that stays cold because of
excessive ventilation.

Actually you have a point and maybe after you reach 18 to 24
inches of fiberglass or R 66 excess venting may not have
much effect. Unfortunately, you can expect most people
don't have that much insulation.