HeyBub wrote:

I'll disagree to the extent of scrapping the turbines. You are
correct that they don't work as efficiently when there's no wind
- although some heat escapes through those 18" holes - but when
there IS a wind, they will move an enormous amount of hot air.
Plus, they do it at no electrical cost!

Anyone that likes to get a tan in the summer will know this:

When the sun comes out from behind the clouds, the wind mysteriously
dies down. Then when the clouds come back - so does the breeze.

That fact doesn't help you when your chosen method of active ventilation
is wind powered.

Attic fans (typically 1/8 or 1/10 hp) consume pennies of electricity a
day. Worth the cost when they give you a reliable, dependable CFM of
air movement when you want it.

And speaking of ridges, be sure to install a ridge vent. These
are dirt cheap and will probably give you the biggest bang for
the buck.

Depends on the style of roof.

Again, I'll slightly disagree. You're correct that one can't
have too much soffit venting.

Once upon a time, soffits were faced with 1/4 plywood, and you had to
buy and install screened vents that were visible and you had to do a
nice job of cutting the hole and positioning and installing the vents so
you wanted to install the minimum necessary if you were the builder.

But it was a pain in the ass as a home owner to paint the soffits every
5 or 10 years so you got them covered in aluminum, and with slotted
sheeting it wasn't a hassle anymore to create venting anywhere you
wanted it - including the entire length of the soffit. The only problem
is that unless you cut more holes in the original plywood facing, the
extra aluminum venting will do you no good.

The usual standard is one sq ft of soffit venting for every
150 sq ft of living space.

For new construction, you don't even need to put the 1/4" plywood facing
on the underside of the soffit any more. Just mount your J-channel and
slide the perforated aluminum soffit sheeting into place.

The problem with having one vent every 4 or 6 rafters is that you won't
get much airflow along those rafters that don't have a vent down at
their soffet end. Air will preferentially flow along those rafters that
do have a matching vent where they meet the soffet.