Does anybody have any studies that discuss the pros of attic ventilation (i.e. open soffits and ridgevents).

I have heard that they are over rated and mostly created by the asphalt shingle industry.

There's tons of research results on this both at the Texas A & M website, the Florida Solar Energy Center, and Building Science Corp websites. According to BSC studies at worst-case sealing the ventilation and even adding insulation under the roof deck results in a ~10% reduction in shingle life (in cooling dominated climates.) The COLOR and roof pitch has a larger effect on average & peak shingle temps than the ventilation provsions under it.

There's about R1 of wood + roofing felt isolating the shingles from the ventilation air, and R0 between the shingles and the great outdoors- they radation & convection cool quite nicely to the outdoors, and the ventilation under the roof decking is a secondary factor. Higher roof pitch convection cools fairly well, but under 2:12 it can stagnate a bit (which is why CA Title 24 requires low solar-absorption, high infra-red radiating roofing materials for pitches under 2:12.)

The bottom line is, the effect on shingle life is very slight on roofs with of higher than 2:12 pitch. It has only very modest effects on attic temperatures, and can even increase the cooling load on less-tight houses by driving infiltration losses- the attic stays cooler because it's sucking mechanically cooled air into the attic.

Roof/attic ventilation's primary value has more to do with humidity-purging in heating dominated climates, to limit the amount of condensation of humidity leaking into it from conditioned space onto roof decking & rafters, etc. to create rot & mold conditions. But since the openings drive a chimney-effect, it also INCREASES the amount of air leaking from the warm-humid conditioned space into the attic- something of a solution-problem if undersized, and an increase to the heating load to buildings not well-sealed at the attic floor.

Great post. Ton of good information in there.

as a quick clarification, when you saying heating dominated climates vs. cooling dominated climates, you are referring to the actual HVAC end of the equation and not the outside temperature. i.e. heating dominated climate would be those areas North with longer winters and cooler exterior temps...correct?

Yes- heating dominated means there are more heating degree-days per year than cooling degree-days (more heating load than cooling load to the systems.)  This includes most of the lower 48 of the US (and all of Canada.)  Cooling dominated is the converse.

It's easy to figure in most places, but not always. If you're not sure, look up the annual HDD/CDD numbers of the nearest city here:

http://www.climate-zone.com/climate/united-states/

It's affected by many things such as altitude, proximity to water, and prevaling winds, etc. and can't be assumed on a state-by-state basis. for example within GA,  Atlanta is heating-dominated, but Savannah is cooling-dominated. Similarly in AZ, Winslow & Flagstaff are strongly heating dominated, whereas Phoenix & Tucson strongly cooling-dominated.  But north of the Mason-Dixon, it's pretty much heating-dominated.

Mixed climate places like Jackson Kentucky or Meridian Mississippi are pretty much right on the balance point, heating-dominated some years, cooling dominated others.

Around here, most attics are ventilated because people don't want ice dams forming.

Generically, if you are interested in all kinds of things that relate to saving energy in a house, I recommend getting the free HEED 3.0 software and loading in your climate data.

what about soil for green roof applications?

And yet around here people insulate their roof decks because they don't want ice dams forming, since attic ventilation alone doesn't always quite cut it. Clearly YMMV.

Another thumbs-up for HEED 3.0- it's definitely worth spending the time (modeling the problem) before spending the dime (on stuff that turns out to have been a lesser factor than others you had mis-guesstimated.)